Physical Properties of the Metal Cobalt. - Industrial & Engineering

Ind. Eng. Chem. , 1915, 7 (1), pp 6–17. DOI: 10.1021/ie50073a004. Publication Date: January 1915. ACS Legacy Archive. Cite this:Ind. Eng. Chem. 1915...
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T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y

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goes in the expression of appreciation, t h e degree of its knowledge of the most important characteristics of m a n as indicated b y his inner motives a n d desires a n d t h e condition of his mind as he goes t o his home. Finally, all of these elements should be carefully ap-

Vol. 7, No.

I

praised a n d t h e average should be the rating of t h e company. Mr. Hartness thinks t h a t a n investor, considering this h u m a n rating along with t h e treasurer’s statement, would seldom make a mistake in estimating the true worth of a n industrial organization.

ORIGINAL P A P E R S ~

~

~ _ _ _ _ _

~

PHYSICAL PROPERTIES OF THE METAL COBALT’ By HERBERTT. KALMUSA N D C. HARPER Received October 1, 1914

This paper is t h e third of a series describing investigations of t h e metal cobalt a n d its alloys. It is a report on a large number of measurements made a t this laboratory of some of t h e important physical a n d mechanical properties of metallic cobalt. T h e properties which have been particularly studied are: 6 - ~ o l l i n g a n d ~~~~i~~ I-Density Properties 2-Hardness , - ~ l ~ ~Resistance ~ ~ i ~ 3-Melting Point 8 - - ~ ~ a g n e t i cpermeability 4-Tensile Strength 5-Compressive Strength 9-Specific H e a t pREpARAT1oN

OF

’OR

THE S T U D Y O B

ITS PHYSICAL PROPERTIES

It is true of cobalt, as of most metals, t h a t its physical properties are often greatly influenced by t h e presence of small percentages of impurities. It is well

~~

oxide was obtained from t h e smelters, a n d after a crude purification, was reduced t o form what we shall call “commercial cobalt;” also t h e commercial oxide was purified to a high degree, f r o m which has been prepared what we style “Pure cobalt.” These two names are used in this Paper largely for brevity a n d convenience; t h e analysis of each sample is given with the d a t a of its Properties. The Properties of each of these have been measured a n d will be discussed separately. T h e methods of preparation of t h e pure a n d commercial cobalt used in these researches are given in t h e ~ original l paper, a n d outlined in “Preparation of Metallic Cobalt by Reduction of t h e Oxide.”l coLoR-Pure metallic cobalt very much resembles nickel in color, although, when plated a n d polished under proper conditions, while beautifully white, it possesses a slightly bluish cast. Sometimes i t deposits as a black matte. Metallic cobalt which has been reduced from t h e oxide a t a sufficiently low temperature is a gray powder.

TABLE I-DENSITY OF COBALT All samples were cast from just above melting point in an iron mould and allowed t o cool in the mould Except in cases noted, all samples were then turned in the lathe t o their final form DENSITY Sample ANALYSIS Form of Special __h__ DATE sample treatment Value atOC.2 N‘iOM;ERCIAL CoBALT”-~nann’ealed Co 96 8 Fe 2.36 s 0.022 Dec. 8, 1913 Cylindrical bar None 8.7997 1 8 . 5 See Fig. I X log { N i 0:56 C 0.063 P 0.017 CO 9 6 . 5 F e 1.27 S 0.054 Feb., 1914 Thin cylindrical bar None 8.7690 17.0 See Fig. I V 130 { S i 2.0 C 0.305 P 0.015 Average of 5 Co 9 7 . 8 F e 1.46 0.02 Si 0.02 Feb., 1914 Cylindrical bar Sone 8.6658 1 7 . 0 See Fig. VI11 87c { S i 0 . 5 C 0.18 P Trace Ca Trace Average of 4 PURE COBALT-Unannealed Si None Jan.-Feb., 1914 Cylindrical bar None 8.7562 1 7 . 0 See Fig. I Co 9 9 . 9 Fe 0.20 S 0.017 C None Ca None Average of 6 H 2 1 2 { Ni None Apr. 3, 1914 Wire of 0.0901 cm. diam. Swaged, 8.8490 1 5 . 0 See Fig. I11 Si 0 . 1 4 Co 9 8 . 7 1 F e 1.15 S 0,012 H 2 1 4 ( S i None C 0.039 P 0.010 Ca None s e e p . 11 H 193 N. Co 9 9 . 1 F e 0.80 s 0.021 S o v . 15, 1913 Cylindrical bar Sone 8.7889 20.0 1 Sone Ca Trace s 0.019 Si 0 . 0 2 Jan.-Feb., 1914 Cylindrical bar Sone 8.7732 1 6 . 0 See Fig. I1 Co 99.73 Fe 0.14 H 2 1 3 ( N i None C None Average of 3 PURE COBALT-Annealed Co 9 9 . 9 Fe0.20 S 0.017 Si None Jan. 1 2 , 1914 Thin cylindrical bar Annealed 8.8105 14.5 H212 i None C None Ca None from 700‘ C. from 700’ C. PURE COBALT-Rolled H 213 S 0.019 Si 0.02 Jan. 19. 1914 Thin cylindrical bar Swaged 8.9278 1 4 . 0 C c. 9 9 . 9 F e 0.20 S 0.017 Si S o n e Jan. 23. 1914 Wireof0.0840cm.diam. Swaged 8.9227 1 9 . 0 H212 (N 1 None C None Ca hTone

s

{

IN

{E

known, for example, t h a t less t h a n 0.01 per cent of arsenic in copper is sufficient t o account for a drop in its electrical conductivity2 of 3 . 3 per cent. Similarly, for cobalt we find t h a t a few tenths of a per cent of impurities often doubles or trebles its electrical resistance (see Tables VI a n d V I I ) . T h e cobalt for these investigations has been prepared by reduction of cobalt oxide, C0304. Commercial ‘Authors’ abstract of report under the above title t o the Canadian Department of Mines. Published b y permission of the Director of Mines, Ottawa, Canada. T h i s publication is one of a series on the general investigations of the metal cobalt and its alloys, with reference t o finding increased commercial usages f o r them. These are being conducted a t the School of Mining, Queen’s University, Kingston, Ontario, for the Mines 6 (1914), 107 Branch, Canadian Department of Mines. See THISJOURNAL, a n d 115. J. H. Dellinger, “The Temperature Coefficient of Resistance of Coppel;,” U. S. Bureau of Standards, Bull. 7 (1911). 79.

I-DEXSITY

(SPECIFIC G R A V I T Y )

The densities of both cast a n d rolled cobalt were determined in this laboratory by the Archimedes method. -4 sphere or cylinder of the material was mreighed, using a delicate balance, both in air a n d under water. I n t h e computations t h e weighings were corrected for the buoyancy of t h e air, a n d the measurements reduced so as t o be expressed in terms of water a t its maximum density. Table 1 gives the results. A number of density determinations of metallic cobalt, as made b y other investigators, are recorded in t h e literature, most of which, however, were made at an date, and very little is said Of the nature of t h e metal. T h e following table of values is taken 1 THIS JOURNAL,6 (1914), 107; Bull. 259, Mines Branch, Dept. of Mines, Ottawa, Canada.

T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

Jan., 1915

from t h e more recent a n d probably more accurate of them:

-........

DENSITYO F COBALT Other workers

Kalmus and Harper

Tilden(a). 8.718 21° C. Unannealed 8.7918 G. Neumann and F. Strenintz(b).. 8.6 Annealed 8.8105 Copaux(c) ........ 8 . 8 15 ‘c. Wink!er(d) . . . . . . . 7.9678 ... Swaged 8.9253 ( a ) Chemical N e w s , 78 (1898),. 16. ( b ) Monutsheftefiir Chemie, Vienna, 12 (1891), 642. (c) Annulen d e Chimze et d e Physzque, [8] 6 (1905), 508. ( d ) Berg und hiittenmdnnische Zeitung, 39 (18801, 87.

1 7 . 0 a C. 14.5’ C. 16.5’ C.

T h e values from t h e literature are generally lower t h a n those measured b y us, no doubt because of impurities in t h e metal, or because of t h e difficulties of casting without occluding a certain amount of gas.

t h a t we have used for cobalt, a n d a table of these values is given below for comparison. I n each instance t h e value is t h e mean of a number of observations, a n d they are reproducible, on t h e same sample, t o within a few per cent. Different samples of most of these materials give values differing considerably among themselves. This table is given merely t o serve as a rough basis of comparison. COMPARISON TABLE O F BRINELLHARDXESS LOADBRINELL LOAD, BRINELL Lbs. HARDNESS 3500 lbs. HARnNEss COPPER 1000 6 5 . 6 MILD STEEL . . . . . . . . . . . . . 109.9 67.4 Rolled., 1000 Cold rolled shafting.. . . . 126.2 Sheet. . . . . . . . . . . . 3500 75.0 T ~ P S LT E E L .... . . . . . . . ..IJ153.8 Unannealed. . . . . . . 3500 81.9 Crescent”. 130.2 SNEDISH IRON.. .... 3500 9 0 . 7 SPRINGSTEEL... . . . . . . . . . 160.3 1000 68.6 178.0

............ .........

...........

2-HARDKESS

Hardness measurements were made in this laboratory on a standard Olsen hardness testing machine of I O O , O O O lbs. capacity. (Tinius Oisen Co., Philadelphia, Pa.) T h e machine consists of a framework on which is mounted a lever system. T o one end of this lever system a penetrating ball is attached,

7

3500 3500 1000 3500 3500 1000 3500

...

WROVGXTI R O N . .

.......

CAST I R O N . .

COBALT

FOR

75.2 92.0 83.1 100.2 97.8 84.4 104.5

BRIKELL

TOOLSTEEL

SELFHARDENING . . . . . . . . 180.0 “Rex,” before hardening “Rex,” after hardening.

162.1 240.0

Self hardening from School of Mining Workshop, , . ,

259.0

HARDKESS

MEASUREMEKTS-

T h e hardness of cobalt, like t h a t of most other metals,

TABLE11-BRINELL HARDNESS OF COBALT All samples were cast from just above melting point, allowed t o cool in iron mould and turned in lathe Suecial treatments bevond this are noted below. Load 3500 lbs. unless given otherwise Brinell Sample ANALYSIS DATE Special treatment hardness REXIARKS No. “COMMERCIAL COBALT’’ 111.4 121 9,1913 None H 109 C 0.062 S 0.072 P 0,017 100.9 See Fig. I X 1/14/1914 None 12/11/1913 None 104.4 }Metal soft, tough and turns with medium 11 1 . 7 long curling chip 12/22/1913 Kone 9/15/1914 None 100.2J H 214c Co 97.09 Fe 1.45 Si 0 , 0 1 1 9/15/1914 Annealed from 850° C. 138.6 See Fig. V 9/15/1914 Annealed from 1000° C. N i None C 0.067 P 0 . 0 1 0 136.9 See Fig. VI M n 2.04 S 0.012 Ca None 9/15/1914 None 123.9 See Fig. I11 Co 9 8 . 7 F e 1.15 Si 0 . 1 4 N i h’one C None P 0.011 S 0.012 C a None H 211 c 0.10 1/14/1914 None 128.2 Metal soft and medium tough. Xachines with 9/15/1914 None 130.7 long curling chip. See Fig. X Metal medium hard and tough. Machines with S 0.022 P 0.012 H Sic C 0.13 1/16/1914 None 1 3 1 . 0 { curling chip. SeeFig. VI11 12/22/1913 None 119.2 H Eiaande C 0.22 S 0.03 P None 9/15/1914 Quenched from 1200’ C. 132 9 12111,,lg13 Quenched from 12000 15 Me:;i-short grained. brittle and turns with short H 130 C 0.305 S 0.054 P 0.015

’i ’

1

113 8 s o f t and tough. 1 1 6 . 6 { Metal ee Fig. IV

2500 Ibs. Metal soft a n d hrittle. 129.7 Load with short chip 133.4 131.2 105.5 Load 2500 lbs

S

S

0.016 0.015

P P

Fe C

0.80 None

S

11/15/1913

None

n 212

Fe C

0.20 None

S

12/ 9/1913 11/15/1913 11 911914

None None h-one

H 213

H 217

Co Ni

9.99 None

Co 9 9 . 7 3 N i None c o 99.55

Fe C

0.14 None

None None

0.02 C a Trace

S

0.017

0.019

L.L.P

Quenched from 1200’ C. h-one None None

87dandb C 0.36 C 0.37 PURE COBALT H r93 Co 99.1 N i None

H

I,

9/15/1914 1/14’1914 2 1 1,’1913 2 / 1,’1913

1/14 ‘1914 h-one 1/14/1914 Annealed from i O O o C. 1/14/1914 Annealed from 700° C. 9/15/1914

9/15/1914

Annealed two hours at 600° C . . allowed t o cool slowly. a n d again turned in lathe None

while a t t h e other, weights are attached, which, when applied, cause motion of t h e lever system a n d penetration of t h e ball into t h e metal t o be tested. An instrument is mounted on t h e main lever which measures automatically t h e actual penetration of t h e steel ball t o 0.0001of a n inch. All hardness measurements of t h e metal cobalt made b y us have been computed in t h e Brinell system, a n d have been made with a sphere of one centimeter diameter, a n d with a load of 3500 pounds, unless stated otherwise. We have measured t h e Brinell hardness of a series of common substances under t h e identical conditions

::

Machines with curling chip.

] Very tough t o turn in lathe

soft a n d brittle. 1 2 8 . 7 Metal See Fig. I 130.8 Load 2500 lbs. soft and brittle. 121.0 Metal See Fig. I1 125.9

Machines

Machines with short chip. Machines with short chip

109 5

is determined t o a greater extent b y its physical a n d mechanical treatment t h a n b y slight variations in i t s chemical composition, if we except t h e presence of carbon. Even our “commercial cobalt” contains b u t small percentages of total impurities of which t h e greater part is iron a n d nickel, and which, in t h e small amounts present, would not greatly affect t h e hardness. Table I1 reports t h e hardness measurements made. I n t h e samples under “commercial cobalt” t h e percentage of carbon is given throughout, a n d t h e other impurities are between t h e following limits:

T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y

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S........ 0.010 to 0.070 per cent

.... .....

Ca.. Si..

F e . . . . . . 0.10 to 1 .O per cent N i . . .... Trace to 0.50 per cent C . . ..... 0.10 to 0.60 per cent

Trace to 0.015 per cent Trace to 0.20 per cent

T h e total impurities in a n y one sample of this "commercial cobalt" rarely exceeded I . j per cent. B R I N E L L H A R D X E S S MEASUREMENT-Asingle measurement of the Brinell hardness is given in full t o show t h e concordance of observations among themselves, a n d the details of computation. This may be taken as typical of the large number of measurements which were made. SAMPLEH 193 Initial reading 0.0344 0.0333 0.0309 0.0321

LOAD,3500 LSS. Indentation (in.) 0.0145 0.0147 0.0156 0.0147 AVERAGE,^.^^^^ in. = 0.379 mm. P total pressure in kg' P -area of depression in mm.* 2arh

DEC. 9, 1913 Reading under load 0.0489 0.0480 0.0465 0.0468

-

Brinell hardness by definition where, P = Load in kg. I = radius of indenting ball in mm. h = depth of depression in mm.

.:

Brinell hardness =

1 3 500 X 2 x *x5 x 2.2

HARDNESS O F COBALT AS

0.39 = 133.4

OBSERVED B Y OTHER IN-

VESTIGATORS-There is very little in t h e literature on t h e hardness of cobalt, except a few more or less qualitative observations. However, a careful measurement seems t o have been made by R. Reur a n d K. Kaneko,' from which t h e y compute t h e Brinell hardness of cobalt t o be 132. C O M P A R A T I V E H A R D N E S S O F N I C K E L A N D COBALT-

For comparison we have measured the hardness of both cast a n d sheet nickel under the same conditions t h a t we have used for cobalt, load 3joo lbs., a n d found t h e m t o be, respectively, 83.1 a n d 8 j . I Brinell, t h e latter for a inch sheet. An independent check test on the hardness of cast nickel gave as a result 76.4. CONCLUSIONS-HARDNESS

I-Table I1 shows the Brinell hardness of cobalt cast from just above the melting point, a n d allowed t o cool in a n iron mould, t o be in the neighborhood of 124.0 (load 3500 lbs.). This is t h e mean of nine observations with a n average deviation from t h e mean of 7.9. 11-The hardness of cobalt cast from just above its melting point is considerably greater t h a n t h a t of either iron or nickel, under corresponding conditions. 1x1-The effect of the addition of 0.060 t o 0.37 per cent of carbon on the hardness of "Commercial" cobalt is not sufficient t o offset the effect of slight variations in heat treatment. T h e measurements are not sufficiently concordant t o warrant drawing general conclusions. 3-MELTING TEMPERATURE O F COBALT A considerable number of melting point determinations of t h e metal cobalt were made in a n Arsem electric vacuum furnace (General Electric Company, Schenectady, N . Y.). These determinations were carried out by .the usual cooling or melting curve method, using pure alumina crucibles a n d alundum lined graphite crucibles. Cobalt has a very sharp melting point, differing in this respect from iron, which becomes plastic as i t 1

Feururn, 10, 257; Chern. Abs.. 191S, p. 3591.

Vol. 7 , No. I

approaches its melting point. With iron t h e actual temperature of melting is not sharply defined, there being a considerable transition region, whereas with cobalt quite the reverse is true. Therefore, the melting point of cobalt may be determined with accuracy by the cooling a n d melting curve method. TEMPERATURE ME.4SUREMENTS-TemperatUre observations were made with a Wanner optical pyrometer, which was checked against a n amyl acetate lamp standard before a n d after each set of runs, in accordance with a calibration certificate from the Physikalisch-Technische Reichsanstalt, a t Charlottenburg. This pyrometer was also used t o measure the melting points of copper a n d nickel during t h e period of its use for t h e determinations on cobalt, which measurements agreed with the calibration curve used t o within a few degrees. For this work the melting point of nickel was considered t o be 1444' C., a n d of copper t o be 1084' C. T h e melting point of nickel, considering our calibration curve from the Reichsanstalt t u be correct, was determined six times as follows: c. 1438 1437 1445 1446 1448 1450

Deviation from the mean 6

7 1 2 4 6

-

-

1444 Mean

4.3' C.

Average

T h e nickel (see Fig. X I ) used for these melting point measurements analyzed as follows: C a . . . . . . . None X . . .............. 99.29 Fe ................

S .................

Si ................

0.48 0.025 0.042

C ........ Xone None

Co

.......

TOTAL,99.84 per cent

The cobalt (Sample N o . 212-see Fig. I) used for these melting point determinations analyzed as follows: c o . . . . . . . . . . . . . . 99.9 C a . . . . . . . None Ni. . . . . . . . . . . . . . . . Kone Si . , . . , . . None C . . . . . . . None Fe . . . . . . . . . . . . . . . . 0.20 s . . . . . . . . . . . . . . . . . 0.017 TOTAL, 100.12 per cent TABLE 111-SUMMARY Date of run 27 1912 Sept. 30: 1912 Sept. 30, 1912 Oct. 1, 1912 Oct. 1, 1912 Jan. 13, 1914 Jan. 13, 1914 Jan. 14, 1914 Jan. 15, 1914 Jan. 15, 1914 Jan. 15, 1914 Jan. 19, 1914 Jan. 19, 1914 Jan. 19, 1914 Jan. 19, 1914 Jan. 19, 1914

OF

RESULTSOF MELTINGPOINT DETERMINATIONS Deviation of single obDetermined melting Doint of cobalt servation from the mean 7 1474' C. 5 1472 5 1472 3 1470 5 1472 0 1467 0 1467 7 1460 14 1453 1 1468 1 1468 5 1462 7 1460 3 1470 5 1462 3 1470

Mean melting temperature,

-

-

1467O C.

Average,

4.4O C.

From these observations the melting point of pure cobalt would appear t o be 1467' C. * 1.1' C. [Note, however, conclusions below, second paragraph. 1 I t should be noted t h a t Burgess a n d Waltenberg' use t h e value 1452' C. as the melting temperature of nickel. If we adopt this value instead of 1444' C. (see below), our value for the melting temperature of cobalt would be practically identical with theirs, namely, I4780 c. 1

United States Bureau of Standards, Bull. 10 (1913),6. 1

T R E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y

Jan., 1915

9

THE MELTINGPOINTOB COBALTAS DETERMINED B Y OTHERINVESTIGATORS pyrometer Melting

Purity

Method of measurement

INVESTIGATOR temperature Per cent Burgess a n d Waltenberg(a) . . , . . Burgess a n d Waltenberg(a). . . . . G. K. Burgess(b). H. Copaux(c). . . .

.

Micropyrometer

1477' C. 9 9 . 9 5

.. 1478' 1464' . 1530

Crucible melts in electric furnace Micropyrometer Interpolation between gold and platinum points

C. 99.95 C. Very pure Not given

Guertler a n d T a m m a n ( d ) . .. . . . . . 1528

98.3 Cooling curve Rest largely Ni and F e

Guertler a n d T a m m a n (e) . , . . . , . . 1468 98.3 Cooling curve Guertler and T a m Cooling curve manir).. . . . . , . . 1505 98.3 Guertler a n d T a m 98.3 Cooling curve m a n ( e ) . . . . . . . . 1455 R . R u e r a n d K. K a n e k o k ) . . . . . 1491 (a) Bureau of Standards, Bull. 9 (1912), 475; Bull. 10 (1913), 13. ( b ) Ibid., Bull. 3 (1906), 350. ( 6 ) Annalen d e Chimie et de Physique [SI 6 (1905) 508. ( d ) Zeitichrift j d 7 anorganische Chemic, 42 (1904). 553. (e) Their value corrected f o r melting point of nickel = 1451 instead of 1484 as taken b y them. (fi Zeitschrift j d r anorganische Chemie, 45 (1905), 223. ( 8 ) Ferrum, 11 (1913), 33-9.

C 0 N C L U S I 0 N S-

M E L T I N G T E M P E RAT U R E

The melting temperature of cobalt, as determined b y us, is 1467 =F 1.1' C. This is for metal 99.9 per cent pure, a n d is t h e mean of 16 determinations by the cooling and heating curve method. This value of t h e melting temperature is based upon

calibration curves, considering the value of t h e melting temperature of nickel t o be 1444' C. If we adopt t h e more probable value 14j2' C., for t h e melting temperature of nickel, our melting temperature for cobalt is 1478"C. * I . I ' C.

4- T E N S I L E S T R E N G T H JIE A S U R E ME N T S The tensile strength tests were made on a Riehle universal standard vertical screw power testing machine (Riehle Testing hlachine Co., Philadelphia, Pa.), of I O O , O O O Ibs. capacity, operated by direct connection t o an electric motor. T E S T BARS-AI~ bars for tensile strength measurements have been "Proportional Bars," as recommended and adopted by the International Association for Testing Materials. Table IV reports t h e data for our measurements on "commercial cobalt" and on pure cobalt. There is almost no literature on t h e tensile strength of cobalt, although Copauxl gives-cobalt 69,000 lbs per sq. in., nickel 58,000 lbs. per sq. in. We measured t h e tensile strength of pure iron a n d pure nickel a t this laboratory, under conditions similar 1

Annalen d e Chirnie et de Physique, [8] 6 (1905), 508.

TABLE IV-TENSILE STRENGTH MEASUREMEKTS OF COBALT All samples (except wires) were cast from just above melting point in a n iron mould and allowed to cool in the mould SDecial treatments bevond this are noted below LBS.PER SQ.IN. PERCENTAGE Tensile Reduc- Elon. Sample ANALYSIS breaking Yield tion in gation No. DATE Special treatment load point area in 2 in. REMARKS "COMMERCIAL COBALT"-Unannealed H 109 Co96.8 F e 2.36 S 0.022 12/ 9/1913 None 48,700 33,800 7 , 7 5 . 5 Fairly fine-grained fracture 12,' 9/1913 None N i 0 . 5 6 C 0 . 0 6 2 P 0.017 52,800 33,800 8 . 7 2;:; { T o u g h and difficult t o machine in Si None Ca None 12/16/1913 None 57,200 15,300 24.5 lathe. Long curling chip Fracture coarsely granular and not uni12/22/1913 None 64,100 9,360 25.4 27.0 form in appearance Fe 1.0 2/15/1913 None c o 98.5 s 0.020 H 15 76,700 33,800 7 . 7 6.5 Ca hTone C 0.18 Ni 0 . 3 Si None P None Co97.8 H 87c F e 1.46 Si 0.020 1/23/1914 Xone 56,100 30,600 5 . 3 Metal medium hard and tough. Long " O Ni 0.5 c 0 . 1 8 Ca None curling chip. See Fig. VI11 s 0.02 P 0.012 Si 0 . 0 2 0 Co98.7 Fe 0.80 H 87f 4/ 5/1913 None 75,000 33,iOO 2 5 . 4 29.7 Very tough t o machine in lathe c 0 . 2 2 'P h-one Ni 0 . 2 S 0 . 0 2 9 Ca None F e 0.80 H 876 Co 98.5 Si 0 . 0 2 0 2/10/1913 None 63,200 33,100 24.1 24.0 H 87d Ni 0 . 2 C 0.37 P None 2/10/1913 None i i . 7 0 0 33,900 2 3 . 8 24.0 S 0.016 C a None C 0.18 H Zl,! S 0.08 P 0.031 12/22/1913 None 31,000 31,000 None None Segregation of impurities. See Fig. X c aIMMERCIAL c:OBALT"- .Annealed H 109 Fe 2.36 Si None 1 / 9/1914 Annealed [rom 700' C. 56,100 29,300 1 3 . 3 13.0 Co 9 6 . 8 Metal soft and tough. Machines with N i 0 . 5 6 C 0.062 P 0.017 medium long curling chip 1/14/1914 Annealed from 700' C. 52,600 31,600 1 3 . 3 s 0.022 Ca None 13.5 See Fig. I X H 2146 Si 0 , 0 1 1 C o 9 7 . 0 9 F e 1.45 5/19/1914 Annealed a t 850' C . 70,500 37,100 5 . 1 8.0 Very fine grain, uniform. See Fig. V Ni None C 0.067 P 0 . 1 0 5/19/1914 Annealed a t 1000' C. 75,200 25,500 6 . 1 10.0 Very fine grain, uniform. See Fig. V I M n 2.04 s 0.012 Ca None H 87c F e 1.46 C097.8 Si 0 , 0 2 0 4/22/1914 Annealed a t 850° C. 60,200 40,800 1 . 5 Very fine grain, uniform. See Fig. VI1 1.5 Ni 0.5 C 0.18 P 0.012 5/19/191 4 Annealed ut 850° C. 55,700 . . . , . , . . . . 2.0 s 0 . 0 2 Ca None 6 / 2/1914 Annealed a t 850° C. 63,800 61,300 0 . 6 1 Very fine grain 0.5 6/ 2/1914 Annealed a t 850° C. 58,000 56,100 0.3 Very fine grain 1.5 6/10/1914 Annealed a t 9.50' C. 57.000 18,000 2 . 5 7 2.0 Fracture fine-grained b u t not uniform in 58,500 20,400 3 . 4 2.0 appearance 65,000 55,000 3 . 1 1.9 62,300 40,800 3 . 1 1.9 Fine-grained fracture 42,600 40,800 0 . 6 1 0.5 56,000 46,000 1.0 1.3 PURECOBALT-Unannealed H 212 Co99.9 Fe 0.20 1/ 9/1914 None 29.600 10,200 1 . 5 2 . 0 Fracture coarse-grained and crystalline S 0.017 1/16/1914 None N i None C None 35,400 31,400 0 . 5 4 . 0 Metal soft and brittle. Short chip 1/23/1914 None 43,400 43,400 None None Fracture coarse-grained and crystalline o.5 Frsatc:uuc;eucEarse with radially crystalline 1/23/1914 None 45,800 25,500 I,5

{ {

1

H213

Co99.73 NiNone

PURE

H212 HZ17 WIRES H213

Fe 0.14 C None

COBALT-Annealed Co99.9 F e 0.20 N i None C None

Co99.2 N i None A1 0.021 Co99.73 Ni None

F e 0.730 C 0.036

S 0.016 Fe0.14 C None s 0.19

S 0.019 Si None CaNone s 0.017 Si 0.091 P 0.0077 CaNone

1/26/1914 None

23,000 23,000 None

iYone

2/ 3/1914 1/23/1914 1/23/1914 1/23/1914 2/ 3/1914

37,900 30,600 30,100 23,000 45,300

None None None None 3.0

None None None None 3.6

Fracture coarse with radially crystalline structure. Metal soft a n d brittle. Short chip Fracture good with fine grain. See Fig. I / Fracture coarse-grained, crystalline. Metalsoft and brittle. Machines with short chip Fracture good, fine-grained. See Fig. 11

1/14/1914 Annealed from 700' C. 1/27/1914 Annealed from 700' C.

41,200 41,200 None 28,100 28,100 None

None None

Fracture coarse-grained, crystalline Fracture fairly fine structure. See Fig. I

6)16/1914 Annealed a t 950" C. 6/17/1914 Annealed a t 950° C.

34 800 26,600 43,600 30,600

None None h-one None

37,900 30,600 30,100 23,000 23,000

'

1/29/1914 Swaged t o wire after 2/11/1914) special treatment 3/24/1914 (see pp. 11 & 12)

101,800 . . . . . . 77,000 . . . . . . 90,500 . . . . . .

0.30 1.3

0.25 1 .O

5.0 1.0 8.3

8.2 2.0 ,, ,

*

\

1

Fracture fine-grained and uniform

DIAM. 0.117 in. 0.124in. 0 . 0 7 6 in.

Fine-grained fracture

T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y

IO

t o those for our cobalt tensile strength measurements. The iron used for these measurements analyzed: Fe ....... . . . 99.9 per cent M n . . , . . . 0.031 per cent 0.023 per cent S . . . . . . . . .. . C u . . . .. . . 0.028 per cent P ........... 0.004 per cent Si ....... . Trace C.

.........

0.010 percent

NiandCo

None

The nickel (see Fig. XI) used for t h e tensile strength tests was t h e same as t h a t used for the melting point determinations. A large series of measurements on nickel a n d iron would be required to fix t h e values of the tensile strengths with any definiteness; our measurements show t h e m t o be approximately as follows: Cast Nickel-Tensile Breaking Load 18,000 Lbs. per Sq. In. Cast Iron-Tensile Breaking Load 23,000 Lbs. Per Sq. I n .

The rate of cooling of cast metals from the fluid t o the solid state is such an importanf factor in determining the mechanical properties of the metal, t h a t it is just as necessary t o know the dimensions of the test bars as it is t o know t h e chemical composition. The above values, for iron, nickel a n d cobalt, all of which have been made under exactly the same conditions, with a standard “proportional” test bar, are strictly comparable, although they should not be compared with values obtained by other observers on bars of different sizes. COKCLUSIONS--TENSILE

STRENGTH

I-The tensile strength of pure cobalt, cast and unannealed, is in the neighborhood of 34,400 lbs. per sq. in. This is the average of I O measurements on cobalt cast from just above its melting point, allowed to cool in iron mould, and machined in lathe t o test bars. 11-The effect on the tensile strength of annealing cast cobalt is t o increase its value slightly, although this effect is not marked. The average value of our determinations was 36,980 lbs. per sq. in. for the annealed samples, as compared with 34,400 lbs. per sq. in. for the unannealed samples. 111-The percentage reduction in area and elongation are small for cast pure cobalt as would be expected for the pure metal. Iv--The tensile yield point for pure cobalt is in general very close t o the tensile breaking load. v-The tensile strength of pure cobalt increases very rapidly as the metal is rolled, as is common for most metals. It may easily reach over I O O , O O O lbs. per sq. in. by being swaged down t o a wire. VI-The tensile breaking load of pure cobalt, cast from just above the melting temperature, allowed t o cool in iron mould a n d turned in lathe t o test bar, is greater t h a n either t h a t of iron or nickel prepared a n d tested under the same conditions. “COMMERCIAL COBALT.” vII-The effect of the addition of carbon is to increase the tensile breaking strength of cobalt very markedly, the value rising from 34,400 lbs. per sq. in. for the pure cast and unannealed metal t o in the neighborhood of 61,000 lbs. per sq. in. for cobalt carrying from 0.060 t o 0.30 per cent carbon. More exactly, the average of eight measurements, with a carbon content of approximately 0 . 0 6 2 per cent, is 59,700 lbs. per sq. in. Similarly, PURE

COBALT.

Vol. 7, No.

I

the ‘average of fifteen measurements, with a carbon content varying in the neighborhood of 0 . 2 j per cent, is 61,900 lbs. per sq. in. However, the average deviation of these individual measurements among themselves is such t h a t no more specific conclusion can be attached thereto. These values refer to cobalt cast from just above the melting point, allowed to cool in iron mould, machined in a lathe, and tested unannealed. The increased tensile strength may not be entirely due to the presence of carbon, for these tests were made on “commercial cobalt.” vm-The effect of carbon a n d other impurities in the “commercial cobalt” is t o greatly increase the percentage reduction and elongation, which rises in most cases well above 20 per cent. 5-COMPRESSIVE

STRENGTH MEASUREMENTS

The measurements of the compressive strength of cobalt were made in the same Riehle universal standard vertical screw power testing machine, of IOO,OOO lbs. capacity, t h a t was used for the tensile strength measurements. T E S T B A R S - A ~ ~ bars for compressive strength measurements were I * / *in. long and 3 / 4 in. in diameter. There is practically no literature on the compressive strength of cobalt. We measured the compressive yield point of pure nickel (see Fig. X I ) under conditions identical with t h e above measurements for cobalt a n d found it t o be ~0,000 lbs. per sq. in. This was for a sample cast from just above t h e melting temperature, allowed t o cool in iron mould, and tested unannealed. C 0 N C LU S I 0 N S-C

0 MP R E S S I V E S T R E N GT H

P U R E COBALT. I-The compressive strength of pure cobalt, cast a n d unannealed, is in the neighborhood of 1 2 2 , 0 0 0 lbs. per sq. in. This is the average of 5 measurements on cobalt cast from just above its melting point, allowed t o cool in iron mould, a n d machined in lathe t o test bars. 11-The effect of annealing on the compressive strength of cast pure cobalt is not very marked; the average of j measurements of the compressive strength of annealed cast cobalt is 1 1 7 , 2 0 0 lbs. per sq. in. There seems to be a tendency t o lower the compressive strength by annealing. 111-The compressive yield point of pure cobalt is 56,100 lbs. per sq. in. for the annealed samples, compared with 42,200 lbs. per sq. in. for t h e unannealed samples. Thus the yield point seems t o be slightly raised by annealing. Iv-The compressive yield point of pure cobalt, cast from just above the melting temperature, allowed to cool in iron mould and machined in lathe t o test bar, is considerably greater t h a n t h a t of either pure iron or nickel prepared a n d tested under the same conditions. “COMMERCIAL COBALT.” v-The effect of the addition of carbon is t o increase the compressive breaking strength of cobalt, the value rising well above 175,000 lbs. per sq. in. by the addition of from 0.060 t o 0.30 per cent carbon. These values refer to cobalt cast from just above the melting point, allowed to cool in

Jan., 1 9 1 5

T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y

iron mould, machined in lathe, a n d tested unannealed. The increased compressive strength m a y not be entirely due t o t h e presence of carbon, for these tests were made on “commercial cobalt.” VI-The effect of carbon a n d other impurities in t h e “commercial cobalt” does not seem greatly t o affect t h e yield point through t h e range of our observation, although on t h e average from 0.20 t o 0.30 per cent of carbon, with t h e other impurities shown, tends t o lower i t from 5 t o I O per cent for both annealed a n d unannealed metal. vII-The effect of annealing “commercial cobalt” is t o lower its compressive strength, our values averaging 140,000lbs. per sq. in. for t h e annealed samples, compared with 183,obo Ibs. per sq. in. for t h e unannealed samples. vm-The compressive yield point of “commercial cobalt,” similarly t o t h a t for t h e pure metal, is slightly

I1

may be readily swaged down from cast t a r s t o wire of a n y desired diameter. S W A G I N G MACHINES-FOr our experiments on the swaging of cobalt, we used a No. 3 Dayton swaging machine, manufactured b y t h e Excelsior Needle Company of Torrington, Conn. With this machine the metal is not drawn out, as is t h e case with wire-drawing machines, but is rather hammered down b y being placed within a pair of dies, carried in a slot in the face of a revolving mandrel, outside of which is a n annular rack containing a number of hardened steel rollers. The dies thus revolve rapidly around the work which is hammered by them as they pass between opposite pairs of rolls on either side of it. With this machine i t is comparatively easy t o swage hard steel into fine wires. The steel will pass through the dies either hot or cold. However,

TABLEV-COMPRESSIVE STRENGTH MEASUREMENTS OF COBALT All samples cast from just above melting point, allowed t o cool in iron mould and turned in lathe LBS. PER SQ. IN. ComprerANALYSIS Special sive break- Yield Sample No. DATE treatment ing load point REMARKS “COMMERCIAL COBALT”-b-nannealed 172,000 29,000 H 876 ‘2098.5 F e 0.80 S 0.014 Si 0,020 2/10/1913 None Ni 0.20 C 0 . 3 7 P None C a N o n e Metal hard and tough. hfachines . medium 178,000 52,100 1/16/1914 S o n e H 87c Co97.8 Fe 1.46 S 0.020 Si 0 . 0 2 0 .’ medium long curling chip with P 0.012 C a N o n e Ni 0 . 5 0 C 0 . 1 8 184,000 47,600 H 87aand e Co98.7 Fe 0.80 S 0.030 Si 0.020 12,/22/1913 None Ni 0 . 2 0 C 0 . 2 3 P Trace C a N o n e H 87d Co98.5 F e 0.80 S 0.016 Si 0 . 0 2 0 2/10/1913 N o n e 184,000 31,200 h7i 0 . 2 0 C 0 . 3 7 P Sone C a S o n e H 109 Co96.8 Fe2.36 S 0,022 12/22/1913 None 197,500 35,000 Ni 0 . 5 6 C 0 . 0 6 2 P 0.017 Low value due t o segregation of imH 211 S 0.080 C 0 . 1 7 P 0.031 12,’22/1913 None 922000 41,000 purities. Fig. X Metal short-grained and brittle. MaH 130 C o 9 6 . 5 2 F e 1 . 2 7 S 0.053 12,’22/1913 S o n e 94s000 36,000 chines with short chip Ni 2.00 C 0.305 P 0.015 “COMMERCIAL COBALT”-Annealed H 211 C 0.17 S 0.080 P 0,031 1/10/1913 Annealed from 700’ C. 98,200 54,300 Impurities segregated. See Fig. X S 0 , 0 1 2 Si 0.011 41’21/1914 Annealed a t 850’ C. 144,000 40,700 Fine-grained and uniform H 214 Co98.71 Fe 1.45 S i S o n e C 0.067 P 0 , 0 1 0 CaiVone M n 2.04 H 87c Co97.8 F e 1.46 S 0.020 Si 0.0 5/19/1914 Annealed a t 850’ C. 124,000 56,500 P 0.012 Ca None 6/17/1914 Annealed a t 950’ C. 148.000 61,000 Ni 0.50 C 0.18 PURE COBALT-Unannealed Metal soft and brittle, turned with H 212 Co99.9 F e 0.20 S 0.017 Si S o n e 1/10/1913 S o n e l ~ ~ very ; short ~ chip~ ~ hTi None C None Ca S o n e 1/24/1914 S o n e 154.000 36.200 H 213 ‘2099.73 Fe 0.14 S 0.019 1/24/1914 None Ni S o n e C None H 193a Co99.6 Fe 0.41 S 0.025 Si S o n e 12/ 9/1913 None 135,800 39,200 H 193 Ni Trace C None P Trace C a N o n e 1/10/1913 None 123,900 54,200 P U R E COBALT-Annealed H 212 Co99.9 Fe 0.20 S 0,017 Si None 1/16/1914 Annealed from 7OOOC. 129,100 63,400 N i None C S o n e Ca S o n e H 213 Co99.73 F e 0 . 1 4 S 0.19 1/16/1914 Annealed from 700° C. 114,300 65,600 M $ $ ~ o ~ ~ ~ d with Ni None C None H 217 C 0 9 9 . 2 0 Fe 0 . 7 3 0 S 0 . 0 1 6 Si 0.091 5/19/1914 Annealed a t 850’ C. 102,000 45,200 5/20/1914 Annealed a t 850’ C. 106,000 65,600 Ni S o n e C 0 . 0 3 6 P 0.0077 Ca None A1 0.021 6/17/1914 Annealed a t 950’ C. 134,800 40,700

.

{

{ {

22,;:;

{

{

raised b y annealing; our values average 39,000 lbs. per sq. in. for unannealed samples, compared with 53,000 lbs. per sq. in. for the annealed samples. 6--MACHINING, R O L L I X G AXD SVI’AGIXG OB M E T A L L I C COBALT T C R X I N G PRoPERTrEs-Pure metallic cobalt may be readily machined in t h e lathe, although i t is somewhat brittle a n d yields a short chip. The addition of small amounts of carbon renders cobalt less brittle and t h e metal then yields a longer curling chip upon turning. S W A G I X G O F CoBALT-Cast cobalt of extreme purity, which has been cast either in iron or sand moulds, whether cooled slowly or rapidly, cannot be directly swaged down t o a fine wire without special mechanical heat treatment. On the other hand, “commercial cobalt” containing small percentages of carbon as described in this paper,

when a bar of pure cobalt, which has been turned in a lathe t o give i t a smooth uniform surface, was placed in the swaging machine cold, i t cracked along its entire length, and broke off a t many places. This was repeated several times with different bars of the metal, each time with the same result, showing t h a t the metal could not be swaged cold,. It became evident t h a t pure cobalt must be given some heat treatment before i t could be swaged a t all. Hence a bar was first annealed from a temperature of 7 0 0 ° C., b y heating i t slowly t o this temperature in a gas muffle furnace, holding i t there for a short time, and then allowing i t t o cool with the furnace, during several hours. It was then heated t o different temperatures before being placed in the swaging machine, with the following results: A t 900’ C., t h e metal crumbled in t h e machine as

T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

I2

Fie. I

x

130

P u m C o e n r . ~ t1 212

ser.; Mrp 8. 1914 Etehing---Strong iodine for 3 minutes Analysis--.Co, 99.9; Pe, 0.20: s. n.017; ~ i , C. ea. si. h-one Density-8.7562 at 1 7 * C. Exposuce--l

Brinell Hardness-128.7 Tensile Breaking Load-37,900 lhs. per sq. in. Melting Point---147X0 C . i l 1 . l " e. specific ~ i t c t r i c a iR C S ~ S L ~ ~ ~ ~ - S B . O Xin-, ohms per C m l

x

x

130 C

i?rpnsurr-i

EeC.;

ik:. 11

Etching-Strong

O

M

coBALI ~ ~ 11213 ~

s, 0.019; si.

at 16* C.

Brinell Iiardnesr--1

21.0

Tensile Breaking Load-45,100

though i t were extremely hot short, although the sulfur content was as low as 0.018 a n d 0 . 0 2 0 per cent. cracked and broke A t 7 o o o C . to ao0" C. i t very badly in the machine. A t joo' C. t o 600' C., however, the bar could be passed through one or two dies without any apparent cracking. It would not go further t h a n this, although t h e bar was reannealed after each pass, and reductions in. bar in diameter of only 0.002 to 0.003 in,, on a were made a t each pass. A t lower temperatures than this t h e metal would crack still more, and hence i t is obvious t h a t thc mctal must be given some special treatment t o render i t more ductile before i t can be swaged down t o a wire. Cobalt, like iron and certain other metals, will absorb considerable quantities of gases when i t is in thc molten s t a t e ; and as the' gases in the metal wiU, i n all probability, have a bad effect on its swaging properties, an attempt was made t o remove any of these gascs t h a t may have hecn dissolved in the metal and which still remained in the solid bar. With this in view, a bar which had been cast in an iron mould was heated slowiy in a good vacuum t o a tempcrature of about joo' C., where it was held for several hours, a t the end of which time the bar was allowed t o cool slowly i n t h e furnace. This treatment is claimed t o have rendered tungsten more ductile; b u t on attempting t o swage a cobalt bar which had been treated thus, very little, if any, improvcment was obscrvcd in its swaging properties. The method which finally succeeded consistcd in sloivly cooling t h e bar from a high temperature, liooC t o 1 1 5 0 ' C., under a high pressure. This was accomplislicd i n the following way: The bar was placed within an iron mould, squeezed tightly by means of clamps, and the whole heated slowly t o the above temperature. The mould, with bar, was then removed from the furnace, a n d t h e outer portions of the mould

Ihs. per sq. in.

I

~ I11 ~ X ~130 COVMZRCLAI. Pro. Cosarr H 214

Bxposuie-2

iodine for 5 seconds

~ n a i ~ ~ 99.73; i ~ - ne. ~ ~0.14; , 0.020; Ni, C. Ca, P, None Deosity-8.77SZ

~

nSny 9, 1914

Vol. 7, No.

i e ~ M; a y I . 1914

Etclli"g--stro"g

iodinr

IO?

!4 minutes

P ~ ,L I S ; si, 0.14; s, n.012; P. 0.011: ~ i ca, . C ,N~~~

A ~ ~ I ~ s ~ ~ -98.7: co.

Density-8.8410

et I S ' C.

This sample shows polyhedinl crystalline structure, with impurities rejected to the boundarien of the crystalline grains.

chilled while the inner portion still remained hot. The consequent contraction through cooling of the outer portio* exerted a considerable pressure on the inner hot bar of metal. The cooling under this pressure continued for three of four hours, after which the metal swaged at a dull red heat with verylittle difficulty. The process of swaging consisted in passing the metal, heated t o a dull red heat, through successive dies, which hammered i t down until a wire of the required diameter was obtained. However, the temperature at which the bar was passcd through the dies had t o be carefully regulated, as the metal apparently would not swage a t all when cold, and when hot only between 500'' and 600" C. By t h u s controlling the temperature, and feeding in the bar very slowly good, smooth, uniform wires were obtained. CONCLUSlO)iS-hlECHANICAL

A N D SPECIAL TREATMENTS

I-Pure cobalt may be machined in a lathe as readily as pure nickel or pure iron, although i t is somewhat brittle and yields a short chip. ~r-"Comrnercial cobalt," containing small percentages of carbon, machines very readily after the manner of mild steel. 111-Cast cobalt of extreme purity cannot be rolled or swaged without developing cracks, unless given a special mechanical heat treatment. iv-Cast cobalt of extreme purity may be rolled or swaged t o a n y extent b y cooling the casting under extreme pressures, iollowed by passing through rolls or dies a t temperatures between 500 t o 600° C.. reducing the bar by small percentages at each pass. v-"Commercial cobalt," containing small percentages of carbon, may he rolled or swaged down from cast bars t o any extent, provided t h a t the metal be worked at a red heat. 7-bEEASUREXENT

OF ELECTRICAL RESISTAXCE

The potentiometer method of electrical measurement, which is in reality a measuremcnt of t h e drop

Jan., 1915

T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

in potential along a known length of wire when a definite current is flowing through it, was employed for our measurements on pure a n d “commercial” cobalt. DESCRIPTION OF APPARATUS-Fig. A is a diagrammatic sketch of t h e electrical circuits as they were used in the potentiometer method of measuring t h e electrical resistance of cobalt. W is a storage battery, t w o volts, which sends a current through t h e circuit W R D A M C B W , which flows in the direction from R t o B. This circuit is known as the potentiometer circuit. AC is a series of fifteen 5 ohm resistance coils, a a d CB is a 5 ohm slide-wire, consisting of several turns of constantan wire mounted on a marble cylinder. St’d is a cadmium standard cell, electromotive force 1.0189 volts, which bears the certificate of t h e United States Bureau of Standards. The standard cell is connected from a point X in the coils AC t o t h e switch T, which is set a t a point in the resistance DTA, such t h a t the electromotive force between T a n d X, due t o the battery W, is exactly equal t o t h a t of the standard cell. This balanced condition is determined by t h e galvanometer G which is connected in t h e circuit of the standard cell by throwing the switch U into the dotted position. The resistance R is adjusted until there is no deflection of the galvanometer, which signifies the balanced condition above mentioned. The resistance coils from A t o C are a set of fifteen 5 ohm coils, a n d the point X is such t h a t ten of t h e m are included between A a n d X. A T D is a standard resistance such t h a t there is included between A and T exactly 0.945 ohm. When the balance was made, there flowed, therefore, through the potentiometer circuit, a current I = 1.0189/50.945 = 1/50 ampere. This adjustment is made so t h a t for this current in the potentiometer circuit, the drop in potential across a n y two adjacent coils along AC is exactly 1 / 1 0 of a volt. T h e switch used is now thrown t o connect a n unknown electromotive force (E. M. F. in the diagram) through the galvanometer, a n d in such a way t h a t the current from the new source flows in the same direction as t h a t from the standard cell. The sliding contact M1 is brokzht t o the zero end of the slide wire, a n d the moving contact M is shifted from C towards A, step by step, until the galvanometer deflection is reversed in direction. M is left st the last point for which a galvanometer deflection is in t h ? same direction as when M was a t C. Then the contact ill1 is moved along the slide wire until t h e galvanometer deflection is zero. The reading of the contact point M gives the value of the Clectromotive force in tenths of a volt, a n d t h a t of M1 from hundredths t o hundred-thousandth‘s of a volt. Thus a very accurate measurement of the unknown electromotive force is obtained in terms of the known standard. The unknown electromotive force in these experiments is not a cell, but is t h e drop in potential along S. S is a given length of the cobalt wire, whose resistance

I3

is to be measured, through which a small current is passing from battery W1 connected as shown in the diagram. I n this latter circuit WIS there is also connected a standard resistance S1 of 0.1ohm. By throwing the switch U1 into the dotted position the drop in potential along SI was measured. Knowing t h e drop in potential along S a n d also along SI, when t h e same current is passing through each, the resistances are known from the following equation: Unknown Resistance S Drop in Potential along S Known Resistance SI = m i n e n t i a l along SI

M E T H O D O F COMPUTATION-The length s between two knife edges, which formed t h e contact points between which the electromotive force was determined, was carefully measured to tenths of a millimeter. The average diameter of the wire was measured t o thousandths of a millimeter, a n d from these data the specific resistance of the wire in ohms per cubic centimeter was calculated t o be 1 RA R=p-orp=-

-

A 1 ’ R total resistance of S in ohms, 1 = length of S in centimeters, A = average cross section of S in square centimeters, U = specific resistance in ohms per centimeter cube.

where

After this measurement the wire was cut t o the exact length S, carefully weighed t o t h e nearest milligram, a n d the density of the wire determined by the Archimedes principle. From these data the resistance

U

D

FIG. A-ARRANGEMENT OF CIRCUITS FOR ELECTRICAL RESISTANCE MEASUREMENTS W and W1-2

Volt and 4 Volt Storage Batteries, Respectively R and Rl-Adjustable Rheostats U and ULDouble-Throw Switches *Galvanometer R and R L S m a l l Resistances for Protection of Galvanometer in Making Adjustments St’d-Standard Cell, E. M. F. = 1.0189 Volts S-Wire Tested SI-Standard Resistance of 0.1 Ohm Correct to 1/25 of One Per Cent, and with N o Temperature Coefficient

E x p o s u r e 2 scc.; May I . 1914

Etching--Strong iodine for 7 mi". Analysir-Co, 96.5; Ni. 2.0: Fe. 1.27; C , 0.505; S. 0.054; P, 0.015 ~ ~ ~ ~ i t ~ - 8 .at7 61 7% 0 C.

n = si.

D = M ...--, R

from which

where

-

V I*

Dp% =

M IA kll

.G,

or A = - M Di' RM or k = T - ,

R = Reairtnnre of S in ohms. M = Mars of S in grams. D c Density Of S, k S~ecificresistance of S in ohms per meter gram, v E Volume of S in cubic centimetew.

-

times i o 4 . T h e following values of the specific resistances of cobalt and nickel are taken from the literature: SPBC~PIC ELBC~P-ICAL RBS~TANEB Specific resistance in ohms per centimeter cube

'remperhtuie Copaux(o) . . . . . . . . . . . . . . . Room . ReuerandKaneko(b) ..... R w m aofman(c) . . . . . . . . . . . . . . noom Knatt C. G . ( d ).......... 10U0C. Knot; C. G . ( d ) . . . . . . . . . . 200- C. Rtichardt ( e ) , 99.8% Co... 20' C .

--

CO~ALT

55 X 1 0 - 7 6 4 X IO-, 97 IO-; I21 X IO159 X 1W7 97 X IO-'

x

NICXrL

64 X IO-' 77.2 X IO-?

io

x

10-7

69 X 10-7 119 X IO-' 103 X lW7 (a) Annolrn dr C h i m i r et de PhysiPXe. 181 6 (1905). 508. (b) Perrum 10 257; Chrm. A b s . , 11s 3591. (C) .'G...r.hl Metallurgy,,. 191S,,P.$9. (d) Prorerdcngr of Ih? Royal Soc~elyof Edinburgh, 18 (1891), 303. (e) Annden de P h w d 141 6 (1901) 832. Procrrdingr of the koyol Socicty,'66 (1900). 50. ( 8 ) Linrei Rend. I l l 16 (1906). 757. I21 (1907). 185. (6) Prorrrdingr bf the Phyrrrol So&. 18 (1902). 57; Philoraphirol ~161 (1902). ~ 177. ~ ~ i ~ ~

cn

a

'The samples of metal which were used were all cast from just above their melting points, allowed t o cool slowly in an iron mould, and thereafter swaged down to wires of given diameters according to the method described under "Swaging of Pure Cobalt." Our results are given in Tables VI and VII. A N E E A L I N G OF WIRES-The effect of annealing on the conductivity of both pure and "commercial" cobalt was studied. I n this connection t h e annealing was accomplished by two methods. (I)

P A S S I N G A SUITABLE ELECTRICCURRENT T H R O U G H

THE WIRE I N vAcuo-The annealing furnace used consisted of a cylindrical giiiss tube about +. ft.long a n d 2 in,

Exposvi-2

in diameter, and sealed off a t the ends with rubber stoppers. Through the ends protruded copper leads and a connection t o a vacuum pump. The slack in the cobalt wire, developed upon heating, was taken u p b y a coiled spring. The approximate temperature was measured by a thermocouple placed against the annealing wire. Ij

For a comparison of k a n d p i t should be noted t h a t k is equal t o fi multiplied by the density of the wire

I

o a r m H 214c em.; M r y 2, 1914 Etching-Strong iodine for 9 min. Aoalysir-Co, 97.09; Fe, 1.45; C, 0.067; S, 0.012; M n , 2 . 0 4 : Si, 0.011; P, 0.010; Ni, Ca, None Annenlrd st 1000' C. Tensile Breaking Load-75.200 lbs. per sq. in.

EXPOYU~P-I set.; May 6, 1014 Etching-Strong iodine for 5 min. Analysis-Co, 97.09; Fe. 1.45; C, 0.067; S, 0.012; M n , 2.04; Si. 0.011; P, 0.010; Ni, Cu, None Annealed at 850" C. Tensile Breaking Load-70,500 Ibs. per sq. in.

of the wire in ohms per meter gram was calculated as f 0110ws : 1

~

Vol. 7 , No.

T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y

I4

3

-

T a a ~ sVI-ELECTRICALRESLSTANCB 08 UNANNBALBD COBALT WIRE D&TA DITS

ti,

z.5

f?

zLI

.n

-

"CoMnmacrN Coa*LT" 21.2 83.25 0 . 0 0 ~ ~ 6 8.w881 229.6 21.0 50.20 o.ooss68 2.4051 231.2

I i 192 1117 ~ ~ 9 9 . 6 3 1117 Ni None 11/7 Fe 0.60 S 0.023 C 0.09

21.8 50.20 0.005568

2.9051

231.5

si Trace e a Trace

H 193 lI/8 ~092.36 11)s Ni 2.73 Fe 4.49 s 0.018 C None H 214 413 ~ ~ 9 8 . 7 1 413 413 N i None F~ 1.15 413 4/6 Si 0.14 4/6 Ca None s 0.012 417 417 C 0.039 P 0.010

PUR*

,H 212 Co 99.9

Xi N o n e F~ 0.20 s 0.017

21.9 75.07 0.01885 22.0 51.67 0.01885

22.5 22.5 22.0 22.0 16.0

74.95 74.95 52.64 52.64 82.56 15.5 82.56 18.0 59.95 18.0 59.95

COSALT

1/22 17 Same 17 Same 17

same17

C None si N~~~

same 14 Same 14 same14

c~~N;;;

same 412 22 14

Co99.6 xixone 0.19' s 0.ou C None Si 0.084 NOD^ P 0.006g

4/4 414 414

92.81 92.81 50.23 50.23 79.41 79.41 48.98

0.006374 0.006374 0.006419 0.006319 0.006319 0.006319 0.006305 0.006305

12.3871 144.4 8.526 144.5

4.304 4.304 3.023 3.023 4.723 4.723 3.429 3.429

0 . 0 0 ~ 8 9 0 4.863 0.005890 4.863 0.005890 2.631 0.00~890 2.631 0.005822 4.113 0.005822 4.113 0.005~22 2.538

48.98 95.38 0.005822 0.006~47 22 95.38 0.006547 23.0 95.38 0.006547 2 3 . 0 95.38 0.006547

2.~38 5.432 5.432 5.432 5.432

105.8

105.8 105.1 104.8 104.2 103.8 104.7 104.7 87.27 88.04 88.08 88.22 86.66 86.80 85.80

x

X IO-'

IO-? IW

1.977 1.992 1.993

X IW'

1.271

x

x

l e i 1.271

x IO-' x X IO-' x

0.9530 0.9530 0.9545 10-7 0.9524 X 1U-' 0.9431 X lW' 0.9403 IO-' 0.9502 X IO-' 0.9502 10-7

x x

10-7

0.7766

X lU-' 0.7834

X IO-'

0.7838

x 1 0 - 9 0.7840 X 1 0 - 7 0.7713 X IW' 0.7727

x x

IU-T

85.55 89.17 IW' 10-7 89.98 X 10-1 89.98 IW 90.26 10-7

x

x

0.7637 0.7616 0.7756 0.7826 0.7826 0.7852

( 2 ) H E A T I N G W I T H I N A N ELECTRIC F U R N A C E I N A C O S

ATMOSPHERE-The furnace used consisted Of an iron tube about 4 ft. long and 2 in. in diameter, wound with suitable insulated nichrome wire. T h e ends, which

.

Jan., 1915

T E E J O U R N A L OF I N D U S T R I A L A N D E R C I N E E R I N G C E E M I S T R Y

x 130 COXYBBCIILC o a ~ r tH 87 c

FmVIX X I30 Com&PBEI~CoB*m€I 87 L

Fro. VI11

Expposur-1 see; MBY6, 1914 Etebing-Srong iodine for I O min. Analysis-Co. 97.8: Ni. 0.50; FE. 1.46: S. 0.020: C. 0.18; Si, 0.020: Ca. F. Trace. Annealed at 850O c. Density-8.6658 at 17' C. Tensile Breaking Load-60,ZW Ibs. per 9q. in.

E x p o s u r e 2 sec.: Mey 5, 1914 EtChing4trong iodine for 1 mia.

Fe, 1 . 4 6 ; Ni. 0.50; C, s, 0.020; s i , 0.020; P,0.012; c a . None

A o a l y s i s 4 o . 97.8; 0.18:

Tensile Breaking Load-56.1W Ibs. per sq. in.

were sealed off with rubber stoppers, were water cooled a n d contained a suitable gas inlet a n d outlet. CONCLUSIONS---ELECTRICAL RESISTANCE COBALT. I-The specific electrical resistance of cobalt wires of extreme purity is 89.64 X IO-' ohms per centimeter cube, or'o.7769 ohms per meter gram,

PURE

Tns~mVII-ELUCTSICAL

RBSISTANCB OP ANNSALBDC o s a ~ i

.

..

.

350 2 Vac.

350 5 200 5 200 5 300 2 300 2 400 2 400 2 5w 2

COI

co*

CO, CO, CO,

co, co, co*

500 600 600 700

2

350 350 350 350 4w 4w

5 Vac. 5 vac. 5 Vee.

I 1 1

700 1 so0 1

'

Vac.

COS COB COI COI

co*

5 Vse.

2 co, 2 co, 500 l.5C01 500 1.5cO. 600 1 Cor 600 I CO, 700 1 CO, 7 0 0 1 co, 800 0.5 co, 8W 0.5 co. APE. 21-23, are all the same vice, annealed

(a) Samples H 214 SeLieE, and ulranoealed. (6) Note drop in resistance between 500° and 600- C

at 18" C. This is t h e average of twelve observations agreeing well among themselves, a n d is for wires unannealed after swaging. This is approximately five times t h a t of pure copper. XI-The effect of annealing cobalt wire of extreme purity i n zlacuo, at about 3 5 0 ° C. for several hours, by passing an electric current through t h e wire is t o diminish its electrical resistance b y about 5 per

x

FIO. IX 130 .connsscrs.cos.ux H io9 Ezporure1/%seec.: May 6, 1914 E t e h i n g 4 V o n g iodine for 30 E ~ C . AnalPi-Co. 96.8; Ni, 0.56: Fe, 2.36; S. 0.022; C, 0.063; P. 0.017 Density--8.7997 st 1 8 . 5 0 . c . Brioell Kardne-I07 Tensile Breaking Iasd-52,600 Ibs. per sq. in.

cent. This is not as much a s is true of some metals, as for example, aluminum, the resistance of which is diminished about xo per cent by annealing for 2 hours a t 2go' C.' XxI-The effect of annealing cobalt wires of extreme purity in an atmosphere of carbon dioxide gas b y beating from a n external source is a t first t o increase t h e resistance, b u t with continued annealing at increasingly higher temperatures u p t o 800' C., the specific resistance drops again. It is particularly noticeable t h a t there is a drop of about 7 per cent i n the specific electrical resistance of cobalt wire of extreme purity, annealed in a carbon dioxide atmosphere a t 600" C. compared with one similarly annealed a t 500' C.. This drop was from I O I X IO-' ohms t o 93.5 X IO-' ohms per centimeter cube. rv-The f a c t t h a t annealing in DUCUO diminishes the electrical resistance of pure cobalt, whereas annealing in an inert gas a t low temperatures increases its electrical resistance, which is again lowered by heating at higher temperatures, tends t o show t h a t t h e specific electrical resistance OF cobalt is largely influenced b y t h e presence of occluded or absorbed gases. t< COMMERCIAL COBALT." v-The specific electrical resistance OF cobalt, as with copper and most other metals, increases tremendously by the addition of small percentages of impurities. Less than 0.5 per cent of impurities may treble t h e electricat resistance. VI-The specific electrical resistance of "commercial cobalt" varies between 231 X IO-' and 103 X IO-' ohms per centimeter cube, for t h e cases we have studied, depending upon t h e nature of the small percentages of impurities present. These figures are for wires unannealed after swaging. vrx-The effect of annealing "commercial cobalt" by passing an electric current through the wire in BQCUO, is to greatly reduce its specific electrical resistance. Annealing in this way a t 350' C. for 5 hours 3

K. Gwnercke, Elmbirian. IP, 450; Chcm. Ab&, 1914, 1049.

Vol. 7 , No.

T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y

16

Fio. X X 130, COMMBRCIAL C o B . ~ i i €1 211 Exposure-i sec.: M a y 5. 1914 Etching-Stions iodine for i mill A ~ ~ ~ Y s ~ s -0-. 1 - c8 .;s, n.080; P, 0.031 ~ r i o c l iHardness--128.2 Tensile Breaking Lo.td--31,000 lhs. per 14. in. This $ample show3 "ghosts" or "ghost lines" because of its impurities. c, S. nnd P. Metids of this kind sre usuuiiy brittle, week and hard, which sre the characteristics of this particular sample BI shown under the tables of prerccding.

reduced the specific resistance b y approximately 14 per cent. vnr-The effect of annealing "commercial cobalt" in a n atmosphere of carbon dioxide gas by heating from a n external source is in genera! t o decrease its resistance. As in t h e case of pure cobalt, there is 3 sharp decrease in resistance i n the sample annealed in an atmosphere of COZ gas a t 600' C. compared with t h a t similarly annealed a t joo' C. These conclusions ail refer t o measnrements on wires made from bars CdSt from just above melting temperature, allowed t o cool in an iron mould, and then swaged t o wires of approximately 0.03 in. diameter, in t h e manner described on pages X I and 1 2 . 8--MAGNETIC

PEKMEASILITY

AND

HYSTERESIS

SUREMEKTS OF P U R E COBA1.T

HEAT MEASUREISEXIS

The specific heat of cobalt was determined by the method of mixtures, and the resnlt is probably accurate t o within 0.j per cent. T h e method employed consisted in heating a weighed amount of metallic cobalt in t h e form of short pieces of wire t o 100' C., by bringing them into temperature equilibrium with steam a t norma! temperature and pressure, a t the same time having them enclosed so t h a t they were perfectly dry. This >vas accomplished by a simple boiler device. When the metal was t h u s brought t o looo C., which temperature was read on a suitable thermometer, and after constant temperature readings on this thermometer had been obtained for a period of minutes; it was dropped directly from the heater into a suitable calorimeter. Prior t o dropping the cobalt a t roo' C .

x

130

PIIRY.NICKBL

Brinell i-Iaidoer3-83.1 7 , 1914 Efrlinig--Nitric acid (SP. 6'. 1.42) for 4 set. ~ n e i ~ s i s - ~99.29; i, *e, 0.48; 0.025; si. 0.042; co. ~ a C. . ~ o o e Exporure--Z

J ~ C ;&lay

s.

Tenoile Breaking Load-I8000 lbs. per 19. in. Melting Point-1444' C. This nickel shows poiyhedial eryrtalline structure of the pure metal.

into the calorimeter, preliminary temperature readings of the water in the calorimeter were made over a period of minutes. These readings were continued with uniform stirring of the calorimctcr liquid, after the introduction of the cobalt, until the final equilibrium calorimcter temperature had been reached. The thermometer was read t o o . 0 1 ~C., and readings were takcn every 2 0 seconds. This method obviously gives us the mean specific beat between looo C. and room temperature, approximately 15 C . HATEnrAr,-The cobalt used for the specific heat measurements was Sample No. H 213 (see Fig. 11) and analyzed as follows: eo

...........

9Y.73

MEA-

A considerable series of measurements on the magnetic properties of pure cobalt have been made in this laboratory, b u t as they are extended in length, and as they have bearing OR certain interesting magnetic cobalt alloys, which are also being studied, these measurement6 will form part of an independent paper, which is i n process of writing. 9--SPECIFIC

rile. X I

I

C ............. None

Si . . . . . . . . . . . . . 0.040 Ca ............ None P ............. None

The mean of 21 series of specific beat measurements, made as indicated above, gives us the Mean Specific Heat of Cobalt between I j-xooo C. = 0.1053.

with an average deviation of single observations from the mean of about o. j per cent. T h e writers wish t o acknowledge their indebtedness t o Professor W. J. Drisko of the Department of Physics. Massachusetts Institute of Technology, Boston, who was good enough t o have several specific beat measurements of our material made under his direction a t the Massachusetts Institute of Technoiogy. These measurements were made on the same material as above. Following are the measurements: SAMPI.. li 213. MARCH 18. 1914 Specific heat Deviation of a single of cobalt obrervnlioo lrom the meen 0.1070

0.0014 0.0019

0.1037 0.1058 0.1060

0.0002

0.0004

__ Mean.

0.1056

~

~

~

e

~n.onio . ~

~

.

k4ean Specific Heat of Cobalt between 15-roo' C. o.ro56 F- o.oooj. T h e following values of the specific heat of cobalt are taken from the literature: =

THE JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY

J a n . , 191j

TEMPERATURE

TEMPERATURE

R ~ N G E SPECIFIC R$NGE OBSERVER C. HEAT OBSERVER C. Tilden(a).. -182 t o 15 0.0822 Copaux(c).. 500 78 t o 15 0.0939 800 15 t o 100 0.1030 1000 15 t o 185 0.1047 CoDaux(d). . 20 t o 100 15 t o 350 0.1087 Kdmus'and 15 t o 435 0.1147 H a r p e r . . . 15 t o 100 Drisko.. . . . . 15 t o 100 15 t o 550 0.1209 0.1234 15 t o 630 Tilden(b).. 20 t o 200 0 . 104 (n) Proceedings of Royal Sociefy, 66 (1900). 244. ( b ) I b i d . , 71 (1903), 220. (c) Comfit. rend., 140.(1905). 657, ( d ) Annulen de Chim+e el de Physqlue, [SI 6 (1905), 508

-

SPECIFIC HEAT 0.1451 0.1846 0.204 0.104

0.1053 0.1053

F r o m these figures t h e t r u e specifc heat a t a n y temperature m a y be computed from o o to 890' C . Specific Heat = 0.10j8 o.oooo4j7t o.ooooooo66t2.

+

+

MI CR 0 P H 0 T 0 G R A P H S

N o a t t e m p t has been made t o make a minute or complete microphotographic s t u d y or analysis of cobalt with t h e small percentages of impurities with which we have t o d o in this paper. Such a s t u d y would be decidedly interesting b u t , unfort u n a t e l y , is n o t possible in t h e time a t o u r disposal. T h e microphotographs shown (Figs. I t o X I ) are rather characteristic, and require no further explanation t h a n t h e notes accompanying t h e m a n d t h e references in t h e t e x t a n d tables. T h e analyses throughout this paper were made by Mr. R. C. Wilcox, part-time assistant i n this laborat o r y ; valuable assistance was rendered in certain of t h e experiments by b4r. W. L. Savell, B.Sc., a n d by n l r K. B . Blake, S.B., likewise both part-time assistants T h e authors wish t o acknowledge their indebtedness t o these gentlemen. RESEARCH L A B O R A T C ROY F APPLIED

ELECTROCHEMISTRY A N D I\f

TALLURGY

QUEEN'SUNIVERSITY, K I N G ~ T ONTARIO ~~V

I7

ciple of t h e procedure rests on t h e fact t h a t t h e gases at different stages in t h e analysis are subjected t o temperatures a t which certain constituents can be removed by a mercury p u m p from certain others which have lower vapor tensions a t t h e temperatures selected. It was found impossible t o make a clean separation in a n y case a t one fractionation, hence distillates a n d residues were refractionated until t h e separation was as complete a s was desired. T h e following groups show t h e constituents in artificial gas t h a t can be separated at different temperatures. T h e first column shows t h e distillates t h a t can be obtained a t a particular temperature a n d t h e second column t h e residues, i. e . , those gases t h a t have appreciable vapor pressures a t the temperatures given: TABLE I-GROUPS SEPARATED FROM ARTIFICIALGAS AT VARIOLX TEMPERATURES

-

DISTILLATES RESIDUES Boiling ---A point Nameand B. P . h-ame and B. P. Name and C. formula C. formula OC formula Liquid air temperatut ' e . -18.50 CI Methane, C H I . . , -165 E t h a n e , C ~ H E. ., . . -93 -103 Propane, C3Hs.. . . -45 -5 1 h-itrogen, Nz.. , . , -195 Oxygen, 0 2 . . . . . . -183 N - b u t a n e ( a ) , C ~ H0I 1 Carbon monoxide, Iso-butane, C4Hm -10 -4 co. . . . . . . . . . . -190 80 Hydrogen, Hz.. . . -253 Below -140° C. Propane, CsHs.. , , -45 Propylene, C3Ha -5 1 Ethylene C ~ H I .,. -103 1 Iso-butylene, "butane, CaHlo.. E t h a n e , &IS.. . . -93 -4 Iso-butane, CIHLO -10 C4Hs.. . . . . . . . Benzene. CoHs. 80 Below -120° C. 1 Iso-butylene, Propane, C3He.. . -45 N-butane, CIHIO.. Propylene, CaHe.. -51 C4Hs.. . . . . . . . -4 Iso-butane, C4H1o -10 Benzene, CeHs.. 80 - 7 ~. 1 0 ~

c -.

K - b u t a n e , C4HlO. 1 Benzene, CsHe.. , , 80 Iso-butane, C4H10 -10 Iso-butylene, C4Hs -4 ((I) T h e boiling point of N-butylene could not be f o u n d in the literature. T h e N-butylene was not separated from t h e iso-butylene; neither was t h e N - b u t a n e separated from t h e iso-butane.

TABLEIT-COMPOSITIOS

THE SEPARAT1'L"NCF THE ILLUMINANTS IN MIXED COAL AND WATER GAS* B y G. A. BURRELLAND I. W. ROBERTSON

I n this paper are shown experiments, made b y t h e Bureau of Mines, t h a t resulted in separating t h e illuminants i n t h e artificial gas of Pittsburgh. This gas is made by mixing I part carbureted water gas with three p a r t s of coal gas. T h e separation was made by fractionally distilling t h e gas in a vacuum a t low temperatures, a n d follows t h e method detailed b y t h e Bureau i n separating natural gasesS2 I n b o t h t h e n a t u r a l gas work a n d coal gas work, advantage was t a k e n of t h e work on t h e subject b y P. Le Beau a n d A. D a r n i e n ~ ,who ~ separated mixt u r e s of t h e paraffin hydrocarbons a n d coa1,gas b y t h e s a m e method. T h e Bureau, however, separated t h e paraffin hydrocarbons into single constituents a n d found i t necessary t o refractionate distillates a n d residues in all cases t o obtain pure gases. Le Beau a n d Damiens make no mention of this latter necessity a n d separated t h e paraffins i n pairs. F u r t h e r , there is shown in this paper a simple method for t h e determination of benzene in artificial gas. T h e prin1 Presented at t h e meeting of t h e American Gas Institute, October 20, 1914, New York City, with t h e permission of t h e Director of t h e U.S. Bureau of Mines. 2 Burrell. G. A. and Seibert, F. M.. "Gas Analysis b y Fractional Distillation a t Low Temperatures," J. A m . Chem. Soc.. 36 (1914), 1538-1548. 8 Comfit. rend., 156 (1913), 325; 166 (1913), 797.

OF THE ARTIFICIALGAS OF PITTSBURGHAS ~ N A LYZED BY ORDINARY METHODS (SEPTEMBER 1, 1914) Constituents Per cent Constituents Per cent Carbon dioxide, C O z . , . . . . . . 2 . 6 4 Methane, C H a . . . . . . . . . . . 3 0 . 9 6 E t h a n e , CzHe.. . . . . . . . . . . 1 . 8 2 Oxygen, 0 2 . . . . . . . . . . . . . . . . 0 . 8 1 Nitrogen, N z . . . . . . . . . . . . 4 . i 2 Illuminants.. . . . . . . . . . . . . . . 8.67 Carbon monoxide, C O . . , , . . 1 3 . 3 4 __ Hydrogen, H1.. . . . . . . . . . . . . 3 7 . 0 4 T o t a l . 100.00

I n making t h e analysis in Table I1 t h e carbon dioxide was removed by t h e caustic potash solution, the oxygen by alkaline pyrogallate solution, t h e illuminants b y fuming sulfuric acid, t h e hydrogen by absorption i n colloidal palladium' solution, t h e methane a n d ethane by slow combustion, a n d t h e nitrogen by difference. T h e above gas was next subjected t o fractional distillation a t various low temperatures i n t h e appara-, t u s shown a t Fig. I. A t a is shown a Dewar flask t o hold t h e refrigerant used in cooling t h e gases; b is t h e bulb i n which t h e gases were cooled; d is a gas-analysis burette a n d G another gas container for measuring t h e gases prior t o cooling; e is a pressure gauge for registering pressures i n t h e Topler p u m p ; f is a drying t u b e containing phosphorus pentoxide for removing t h e water vapor from t h e gases; g, h a n d i are containers for trapping t h e gases over mercury as t h e y were removed from t h e p u m p ; h a n d i are provided with 3-way stopcocks. T h e , particular advantage of containers such a s are shown a t h a n d i 1 See Burrell, G. A. a n d Oberfell. G. G.. "The Absorption of Hydrogen b y Colloidal Palladium Solution." THISJOURNAL, 6 (19141, 992.

-