May, 191j
T H E J O U R iVA L 0 F I N D GS T RI A L A N D E 11-G I N E E R I 1?;G C H E M I S T R Y
rows for the careful, 1-igorous and painstaking manner which he has subjected t h e solutions and plates t o the various tests t h a t n-ere required t o establish their commercial importance and value. I
-
RESEARCHL A B O R A T O R OFY APPLIED ELECTROCXEMISTRY ASD M E T A L L U R G Y QUEEN'SUNIVERSITY, KINGSTON, ONTARIO
THE FUSIBILITY OF COAL ASH IN VARIOUS ATMOSPHERES' BS A
C FIELDMER A N D A. E. HALL Received April 1, 1915
3 99
governed entirely by t h e relative quantity of eutectic present and its viscosity after melting. If t h e constituents of t h e ash are such as t o form a relatively large proportion of thinly fluid eutectic, t h e deformation point of t h e cone will lie close t o t h e melting point of t h e eutectic; on t h e other hand, if there is a large excess of some refractory component, such as silica or aluminum silicate, or if t h e eutectic is viscous, t h e excess component will form a rigid skeleton which is not pulled don-n b y t h e flowing eutectic. I n t h e latter case t h e deformation point will approach more nearly t h e melting point of t h e rigid component.
IA TRODLCTIOK
I n connection with a general s t u d y of t h e fusibility of coal ash under various fuel-bed conditions, a t t h e Pittsburgh Experiment Station of t h e Bureau of Nines, considerable oxperimental d a t a have been obtained concerning some of t h e factors affecting t h e softening temperature of ash when molded in t h e form of Seger cones. I t was realized t h a t t h e so-called "fusing temperature" tests made b y this method were likely t o give exceedingly variable results in different laboratories, as numerous investigators have shown in t h e case of Seger pyrometric cones, which are of much simpler composition t h a n coal ash. Indeed, L. S. Marks2 has recently called attention t o differences as great as 390' C. which were obtained on t h e same sample of ash b y two different commercial laboratories. I t , therefore, seems advisable t o present in some detail the results t h a t have been obtained in our investigation in order t h a t fuel chemists m a y fully appreciate the empirical nature of the test.
F A C T O R S I S E L U E S C I X G T H E S O F T E N I K G I?OIKT
T h e rate of deformation is also influenced b y t h e rate of heating. Reactions between different constituents take place before their melting points are reached. Some of these reactions are slom-er t h a n others. Also some constituents have a slow ,time-rate of melting, as, for example, silica and feldspar. These substances can be heated above their melting points a n d yet remain in a crystalline form for some time. I t is obvious, t h e n , t h a t t h e deformation temperature of an ash cone must be affected by ( I ) rate of heating; ( 2 ) size, shape and inclination of cone; ( 3 ) fineness of ash; and ( I ) nature of atmosphere in which the cone is heated. I S F L U E K C E O F I R O X OXIDES
On account of t h e presence of iron oxide in considerable quantities in many ashes, the nature of the atmosphere in which the ash cone is heated has a marked influence on t h e softening point. Under suitable conR E L A T I O N O F S O F T E K I S G T E X P E R A T U R E O F ASH T O ditions iron may exist as metallic iron, pure or alloyed MELTING TEMPERATURE O F EUTECTIC with carbon, as ferrous oxide ( F e O ) , magnetite (Fe304), A complex mixture of oxides and silicates like coal or ferric oxide ( F e 2 0 3 ) . On complete combustion ash has no single, definite melting point. On slowly a t low temperatures, the pyrite in coal is converted heating a sample of ash i t successively shrinks, sinters t o Fep03. According t o TT:alden,l ferric oxide (Fe203) a n d t h e n gradually softens into a more or less viscous dissociates a t 1 3 j o " C . , when heated in air a t atmosslag. F r o m t h e viewpoint of clinker formation, pheric pressure, into magnetite (Fe30a) and oxygen. we wish t o know t h e temperature a t which t h e ash Therefore, in determining t h e softening temperature m a y form a slag of sufficient fluidity t o flow or ag- of a n ash cone in a n atmosphere of air (no reducing glomerate in the fuel bed. Since this temperature is gases present), we are dealing with t h e formation of probably belon. t h e temperature of complete melting slags in which t h e iron component enters t h e reaction of t h e ash, i. e., t h e lowest temperature a t which t h e as ferric oxide or magnetite. Peters2 states t h a t melt on sudden cooling is all con\-erted t o glass, t h e "ferric oxide forms compounds with silica which re"softening" or "flowing" temperature of t h e ash when quire a high temperature for their fusion, and is consemade in t h e form of a cone seems a more likely indicator quently an unwelcome base for slags; although this of clinkering tendencies. substance is an almost invariable constituent of 'The deformation of a cone is also a rough measure oxidized ores. it seldom makes a n y trouble in t h e blast of viscosity, which undoubtedly is a very important furnace, for t h e reason t h a t i t is easily reduced by the factor. I t must. however, be kept in mind t h a t t h e fuel gases t o ferrous oxide ( F e O ) . . . . . . . . deformation of t h e cone does not afford a melting "In the more neutral atmospheres of t h e reverpoint or a n y other fixed transformation based on a n y berating smelter, however, i t is likely t o cause delay change of state. X s pointed out b y Day and S h e ~ a r d , ~b y combining with silica. malting i t more difficult a cone made of silicate mixtures, which are capable t o melt the slag." of forming eutectics, begins t o x\-eaken as soon as t h e On the other hand. if t h e ash cone is heated in a eutectic begins t o melt; its further progress is t h e n slightly reducing atmosphere of hydrogen or carbon Published b y permission of the Director C. S. Bureau of hIines. monoxide! the ferric oxide is reduced t o ferrous oxide L. S. Marks, "The Clinkering of Coal." P o m v , 40 (1914), 932-4. A . L. D a y a n d E. S. Shepard, "The Lime-Silica Series of Xinerals." .41so a full discussion of t h e theory of Seger cones, see "The Physical Chemistry of Seger Cones," by R . B. Sosman, Trans. A m . Ccram. Soc., 1 6 (1913), 482-498.
A m . J . Sci., [41 22 (1906). 267.
1 P. T. Walden, "On the Dissociation Pressure of Ferric Oxide," J . A m . Chem. Soc., SO, 1350. 2 Edward Dyer Peters, "Principles of Copper Smelting." Hill Pub. Co.,
Kew York, 1907, pp. 399-400.
T H E JOCRRNA L O F I S D l - S T R I d L A N D E.VGINEERING which is a strong fluxing agent. Steffe’ found t h e following formation temperatures for various ferrous silicates: Formation temperature 4FeO.SiOz.. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2FeO.Si02.. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Fe0.3Si02. . . . . . . . . . . . . . . . . . . . . . . . . . . FeOSiOz . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Fe0.3SiO2 . . . . . . . . . . . . . . . . . . . . . . . . . . .
C. 1158-1 1 i 4 1162-1183 1162-1 181 1 158- 11i 1 1321-1334
The \Tiscosity of ferrous-silicate slags is lower t h a n when t h e iron component enters t h e reaction in t h e ferric f o r m , a s sh0Xv.n b y Greiner;? SO t h e conclusion seems logical t h a t in general lower softening temperatures m a y be expected if the atmosphere surrounding TABLEI-DESCRIPTION
CHEMISTRY
stituents like silica a n d alumina, so t h a t a n y considerable reduction of iron oxide t o metallic iron would t e n d to increase t h e refractory effect of the silica a n d alumina. Hence, lower softening temperatures m a y be expected in tests made in gas furnaces where some reducing gases come in contact with the ash, while higher results should be found both in furnaces where air only surrounds t h e cone and in carbon or graphite electric furnaces where strongly reducing atmospheres reduce the iron oxides t o metallic iron. E X P E KI Y E X T A L
I n t h e following experiments the authors have AND
ORIGIN OF S I > % P L E S
LOCATION OF SAMPLE h-o. LAB. N o 1 2 3 4 5
6 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55
E58 59 60 61 62 63
15840 15841 15842 15843 15844 15845 15846 15847 15848 16018 16019 16243 16583 16584 16585 16586 16587 16589 17081 17189 17534 17590 18248 14762 17563 7244(a) 7305 (a) 7308 7309(b) 18193 18198 18203 18349 18350 18208 18296 18297 18298 18302 18308 18310 18312 18300 18303 18306 18348 18347 18350 12690 12691( b ) 7 228 (a) 7230 141(a) 1458(b) 13316 7548(b) 7381(a) 7490(a) 7494(a) 7522(b) i534 7536(a) 7159(a)
2
DESCRIPTION Bituminous Biturniiious Hituniinoui B It urn moil j Bituminous Riruminoui Bituminous Bituminous Bituminous Bituminous Bituminous Bituminous Semi-bituminous Semi-bituminous Semi-bituminous Semi-bituminous Semi-bituminous Semi-bituminous Anthracite (buckwheat) Anthracite (buckwheat) Anthracite (buckwheat) Anthracite (buckwheat) Anthracite (buckwheat) Anthracite (buckwheat) Semi-bituminous Semi-bituminous ( c ) Semi-bituminous(c) Semi-bituminous(r) Semi-bituminous(c) Semi-bituminous Semi-bituminous
BED Coal Creek American Sterling Jellico Mingo Coal Creek M a r y Lee Nickel plate Thompson Red stone Pittsburgh No. 5 Pocahontas No. Pocahontas N o . Pocahontas No. Pocahontas No. Pocahontas N o Pocahontas A-0.
’
........ ..........
3 3 3 3 3 3
..........
.......... .......... ..........
Georges Creek Pocahontas N o . 3 Pocahontas No. 3 Pocahontas h-0. 3 Pocahontas No. 3 Pocahontas No. 3 Pocahontas No. 3 Pocahontas N o . 3 Pocahontas No. 3 Pocahontas No. 3 Lower Kittanning
..........
Semi-bituminous Semi-bituminous Semi-bituminous Semi-bituminous Semi-bituminous Semi-bituminous Semi-bituminous Semi-bituminous Semi-bituminous Semi-bituminouq Semi-bituminous Bituminous Bituminous ’ Bituminous Bituminous Bituminous Bituminous Sub-bituminou5 Lignite Lignite Lignite . Lignite Lignite Lignite Lignite P e a t briquettes
(a) Clinker from gas producer.
.......... .......... .......... ..........
..........
..........
.......... .......... .......... .......... ..........
Pittsburgh Pittsburgh Pittsburgh Pittsburgh Pittsburgh Pittsburgh
..........
..........
.......... ..........
.......... ..........
NEARESTTOWN Fraterville Parrish Manring Jellico Fork Ridge Oliver Red Star Jefferson Marvel Lemely Jct. Morgantown Booneville Simmons Bramwell Elk Ridge Big F o u r Jenkin Jones Boissevain
.......... .......... Shamokin ..........
1 Herman SteiTe. “On t h e Formation Temperature of a Few FerroCalcic Slags a n d of a Few Ferrous Slags Free from Calcium, t h e Knowledge of which is Significant for tbe Smelting of Lead Ores,” Dissertation, Berlin, 1908. 2 E. Greiner, ‘Weber die Abhangigkeit der Viscositiit in Silikat schmelzen von ihrer Zusammensetzung,” Inaugural Diss., Jena, 1907, p. 5 5 .
AfINE
STATE Tenn. Ala. Tenn. Tenn. Tenn. Tenn. Ala. Ala. Ala. W. Va. W. Va. Ind. W. Va. W. Va. W.Va. W. Va. W. Va.
COUNTY Anderson Walker Claiborne Campbell Claiborne Morgan Walker Jefferson Bibb Barbour Monongalia Warrick Mercer Mercer McDowell McDowell McDowell Tazewell
Va. Pa. Pa. Pa.
Shenandoah
.........
Lonaconing Pocahontas Pocahontas Pocahontas Pocahontas Pocahontas Pocahontas Pocahontas Pocahontas Pocahontas Ebenburg Bering River Field Bering River Field Bering River Field Bering River Field Bering River Field Bering River Field Bering River Field Bering River Field Bering River Field Bering River Field Bering River Field Bering River Field Bering River Field Greensburg Greensburg Marianna Marianna Marianna Carnegie Batan Rockdale Rockdale Lytle Lytle Calvert Calvert Calvert Elizabeth City
( b ) Clinker from boiler furnace.
t h e cone is able t o reduce all the iron t o the ferrous s t a t e before fusion begins. b u t not t o metallic iron, for in t h e latter e r e n t one of t h e most active fluxing constituents is removed from the system. Most ashes have already an excess of high-melting con-
v01, 7 , KO. 5
Pa. ....
..........
Pa. Pa. Md. Va. Va . Va. Va. Va. Va. Va. \‘a. Va Pa. Alaska Alaska Alaska Alaska Alaska Alaska Alaska Alaska Alaska Alaska Alaska Alaska Alaska Pa. Pa. Pa. Pa. Pa. Philippine Pa.
..........
Alleghany Tazewell Tazewell Tazewell Tazewell
T a ze w e11 Tazewell Tazewell Cambria
.......... .......... .......... .......... .......... .......... ..........
.......... ..........
.......... .......... ..........
.......... Westmoreland U‘estmoreland Washington Washington Washington Allegheny
..........
Milan Milan Medina Medina Robertson Robertson Robertson Pasquotauk (c) Bone coal.
\
Island
Texas Texas Texas Texas Texas Texas Texas A-. C .
studied t h e effect of various factors in the softening temperature of ash, b y making tests on a considerable number of different ashes in different types of furnaces such as are in more or less common use for t h e purpose. Before giving t h e results obtained in each furnace, the coals tested a n d general method of operation will be described. The description a n d origin of t h e coal samples are given in Table I, a n d t h e analyses of the ashes and partial analyses of t h e coals in Table 11. As may be
Nay,
IQIj
T H E JOL-RN-4L O F I X D C S T R I . 4 L A S D EXGIAVEERISG C H E A f I S T R Y
seen from a n inspection of these tables, t h e series of fuels tested include a n t h r a c i t e ? bituminous, semibituminous, sub-bituminous: lignite a n d p e a t ; t h e compositions of t h e ashes cover a fairly wide range, silica varying f r o m 12.3 t o i 6 . 0 Per c e n t ; alumina f r o m 8.6 t o 34.7; ferric oxide f r o m 3.8 t o 69.7; lime f r o m 0.6 t o 18.6; a n d magnesia f r o m 0 . 2 t o 10.0 Per cent. T h e coal samples were ground to 6 0 mesh with crusher. rolls a n d ball mill a s described i n our Technical P a p e r 8.’ T h e 60 mesh material was spread Out 011 shallow, 6-inch, fireclap roasting dishes, a n d completely ashed with occasional stirring i n a muffle furnace at a t e m p e r a t u r e n o t exceeding 7 5 0 ’ c. All TABLE11-PERCENTAGEANALYSES OF ASH A N D D R Y COAL ANALYSES O F ASH Alz03 Fez03 Tio2 CaO hlgO xa20 K20 h:[:c
Sample No, sioz 1 35.7 2 47.3 3 55.8
$ 10 11
12 13 14 15 16 17 18 19 26 27
28
29 49 51
52 53 54 55 56 57 58 59
60 61 62 63
Dy
23.5 34 6 33:s
32.9 9.8 5.0
;:
1;:;
1.2 1.8 0.9
:::;2;: ;$:!i:; .\:: ;:$ 6i:; y::
38.4 50.4 37.1 54.8 54.8 54.1 37.2 51.1 51.8 56.1 68.9 69.4 64.7 69.6 54.7 54.5 53.2 54.6 56.8 15.2 47.9 46.2 43.2 52.5 47.5 39.3 46.5 76.0
24.2 2 2 . 4 24.0 20.4 17.6 35.9 27.0 7.8 29.2 6.9 24.8 9.4 25.5 11.8 25.2 10.1 25.0 9.0 31.4 5.0 21.4 4.5 21.5 4..8 23.2 4.7 19.7 5.2 32.9 8.9 27.0 12.1 26.0 15.8 25.7 1 2 . 4 28.2 1 1 . 3 8.6 13.3 23.7 5,5 24.3 6.2 16,9 7,1 21.5 8.8 29.1 5.3 24.8 3.8 28.4 5.2 ii., 4.5
3.2 1.3 1.5
1.1 0.4 0.7
0.3 2.1
0.5 0.1
::: h:: i:: ;:: ::;i:; :::y:: :::i!:
0.9 0.2 0.9 1.5 0.6 1.4 1.9 1.6 1.5 1.0 0.i 0.8 0.8 0.4 0.9 0.4 0.7 0.6 0.8 10.0 3,3 3.0 l., 2.4
0.3 1.0 0.4 2.2 1.9
1.9 1.0 1.8 1.9 2.1
1.4 0.8 1.3
0.4 0.9 0.8 3.1 0.5 1.4 0.5
3.8 0.3 2.3 0.5 1.0 2.8 5.6 3.1 4.3 0.5
!:: 7:; ;:; ::; g:: ;:: i:! y:? A:;
1.1 1.2
0.)
1.6 1.8 2.3 1.5 1.8 2.0 1.9
2.6
2.0 2.6 2.2
...
1.8 1.4 1.4 1.2
...
2,0 1 8 1:6 1.6 2.0 1.9 2.0 1.0
;::
, . i
1.7 3.2 1.6 1.4 4.0 12.6 5.1 4.0 1.0 2.0 1.6 1.2 2.0 1.6 1.5
1.0 4.3 1.0 18.1 18,6 18.5 12,2
14.4 14.0 14.9 16 1 2:s
2.2 I.,
2.3 3.1
1.0 0.8
0.7
0.6 0.5 0.3 0.4 0.6 0.5 0.3 0.6 0.6 5.3
o.4 0.6
0.5 0.2
1.9 1.6 1.3 1.6 1.8 o,2 0.5
o,2 o,3 0.5 0.4 0.2
0.7
1.0
of t h e ash was finally p u t t h r o u g h a a n d thoroughly mixed.
0.1
...
i:5
... ...
0:4
...
26:Y ,,_
lb:o ...
3.1 1 7 0:8
10.8 17.4 15.6
0.5
1.1 2.5 2.2
2.1 2., 5.5
1.9 10.9 11.5 0.i 8.0 0.7 7.5 0.6 7.1 0.6 5.9 0.6 6.8 0.7 5.6 0 . 7 21.5 0.6 1 7 . 2 0.i 14.8 0.7 14.8 0 . 7 14.1 0 . 9 11.1 1.7 11.4 1 . 7 11.4 1 . 4 12.5 1 . 8 12.3
i : j 12:E ;:: ;$:;
0.2 0.3 0.4 0.2 0.9
12:;
100
mesh screen
...
...
1.4 1.4 1.4
16.6 16 6 32:s
PREPARATION O F C O S E S
Sufficient ash t o make t h e desired n u m b e r of cones was transferred t o a n a g a t e m o r t a r , moistened with I O per cent
FIG. I-BRASS CONEhIOLD
dextrin and worked i n t o a plastic mass with a s p a t u l a or pestle. After moistening t h e brass mold (Fig. I) with kerosene to prevent sticking, the plastic material was firmly pressed into it a knife spatula, and the surface off smooth to make a neat solid triangular The
was then pushed out of the mold by applying F. 11. S t a n t o n a n d A . C. Fieldner, “ M e t h o d s of Analyzing Coal and Coke.” Technical P a p n 8 , Bureau of Mines (1913), pp. 7-9. 1
401
a small knife blade a t t h e base. W i t h a little practice a n d proper lubrication of t h e mold this can be done a t once after molding viithout waiting for t h e cone t o d r y . A%fterdrying, t h e cones were mounted i n a refractory base made u p of a mixture of t w o p a r t s of kaolin t o one p a r t of alumina (A1203). This mixture wits moistened with water t o m a k e it workable a n d enough t a k e n for t h e base t o be made a n d spread upon a sheet-iron plate; small hole \vas made i n t o lvhich t h e cone TTas set a n d the base material Tyorked around t h e b o t t o m of t h e cone so t h a t i t Yvould be firmly set at t h e desired inclination i n t h e base. T h e iron plate n-as t h e n p u t on a hot-plate a n d t h e mounted cones dried slowly until all water w a s driven off. T h e dext r i n was t h e n burned out b y igniting t h e mounted cones i n a muffle, after which t h e y Rere ready for use. I n t h e earlier experiments t h e cones mere made directly from t h e I O O mesh a s h ; later i t was found t h a t grinding t h e ash t o a n impalpable powder (or a t least t o pass 2 0 0 mesh) made a more substantial a n d more easily molded cone t h a n I O O mesh material. F o u r different sizes of cones were used: S o . 1, side of base No. 2, side of base KO.3, side of base No. 4. side of base
I/, 1/1 3/16
Liz
inch, height 1 inch inch, height 11, z inches inch, height 1 inch inch, height 21,‘~inches
G E N E R A L METHOD O F H E A T I N G
T h e general procedure i n making a softening temperat u r e determination was t h e same with all t h e furnaces used, t h o u g h necessarily t h e details varied i n t h e differe n t furnaces. T h e test piece vias p u t i n t o t h e cold, or nearly cold, furnace a n d t h e f u r n a c e was heated at t h e r a t e of I O t o I j o per minute u p t o a point n o t less t h a n 2 0 0 ’ C. below t h e probable softening point, at which point t h e r a t e (usually z or j” per minute) which h a d been adopted for t h a t particular determination was begun. T e m p e r a t u r e readings were t a k e n every j minutes, a n d more frequently when approaching t h e softening t e m p e r a t u r e . Observations of t h e appearance of t h e cone were m a d e a t least as often as temperature readings ere taken, special care being t a k e n t o note a n y deformation or warping due t o shrinking before actual softening began. T h e point of initial softening or deformation was t a k e n a s t h e t e m p e r a t u r e where t h e first noticeable bending, rounding a t t h e t o p , or swelling of t h e cone took place. Warping of t h e cone d u e t o shrinkage was not considered as t h e beginning of fusion. T h e softening point, deformation point, or “fusion p o i n t ” so-called, was t a k e n as t h e t e m p e r a t u r e n-here t h e apex of t h e cone h a d bent over t o touch t h e base, o r , failing t o bend, h a d fused down t o a l u m p or ball. Sketches (Fig. 2 ) were made of t h e appearance of t h e cone a t t h e initial a n d final deformation points a n d a t several intermediate points of deformation, with t h e corresponding temperatures. Immediately after reading t h e t e m p e r a t u r e corresponding t o complete deformation, t h e current or other source of heat was reduced so t h a t t h e appearance of t h e cone could be verified by examination after remol-a1 from t h e furnace.
T H E J O U R N A L O F I N D U S T R I A L A N D EiZ'GILZ'EERIA7G C H E M I S T R Y
402
T E DIP E R A T U R E 11E AS U R E 11E N T S
T h e t e m p e r a t u r e measurements were m a d e i n t w o ways: ( I ) b y means of a Heraeus P t - P t R h t h e r m o couple with Siemens a n d Halske high-resistance millivoltmeter, in t h e platinum-resistance, Meker a n d muffle Yo. 2 furnaces, a n d t h e down-draft ceramic kiln; ( 2 ) b y means of a W a n n e r optical pyrometer i n t h e molybdenum, carbon-resistance, a n d N o r t h r u p f u r naces. T h e thermocouple a n d millivolt meter were
hhKQa
Original
1240"
1280'
SAMPLE No.16
1300°
1322"
Good bend.
hdaa,,
Original
1330'
13600
SAMPLE No.16
1386O
1400"
1407'
Bent and melted to a ball.
LhagQ,
Original
ll2P
118S0
SAMPLE No.6
Original
1380"
SAMPLE
1390"
1223O
124Lp
1304'
.a 1345'
Beniand puffed.
1400°
5'01. 7 , N O
j
of K a h l b a u m ' s p u r e copper or Kahlbaum's pure nickel in place of t h e cones a n d noting t h e a p p a r e n t melting t e m p e r a t u r e . This was clone a t least once a w-cek, a n d a t t h e beginning a n d t h e e n d of each series of tests. T h e results obtained in these checks will lie given in t h e discussion pertaining t o each furnace. R E S VL'I S 0 B T AI S E D I S D I F P E R E S T P U R S A C E S A-UEKER
MUFFLE F C R S A C E NO.
29
This furnace (Fig. 3 ) is a simple gas muffle furnace. It consists of a sheet-iron shell, with a refractory fireclay lining. T h e muffle Q is of magnesite a n d rests on t h e front of t h e furnace a n d on t w o points at t h e rear. E x c e p t t h a t a t t h e front i t is entirely surrounded by t h e combustion space over t h e hIeker burner b , which is supplied with t w o inlets, one for gas a n d one for air under pressure, t h e gas burns under a n d a r o u n d t h e muffle a n d t h e products of combustion pass o u t of t h e chimney. I n order t o a t t a i n t h e higher temperatures it was necessary t o a d j u s t t h e gas a n d air so t h a t a slight flame issued from t h e chimney. I n operation, t h e cones c, generally four i n n u m b e r , were set in one base a n d t h e base raised a b o u t 3 / 1 ~ inch from t h e b o t t o m of t h e muffle b y small s u p p o r t s a t each e n d . T h e f r o n t mas closed b y a n asbestos board door, d , with a slit in i t just large enough t o a d m i t t h e thermocouple e, which could b e moved so t h a t t h e couple could be placed very close t o each cone a s i t went do-ivn. T h e thermocouple was protected f r o m reducing gases b y a glazed h l a r q u a r d t t u b e 6 m m . in diameter a n d closed a t one e n d . T h e maximum variation in t e m p e r a t u r e i n moving t h e couple along
No.11 Bent and melted to a ball.
F I G .Z-APPEARANCE
OF
ASH CONESAT VARIOUS S T A G EOF S SOFTENIKG
s t a n d a r d i z e d f r o m t i m e t o time in t h e physical laborat o r y of t h e Bureau under t h e direction of D r . J. K. Clement b y comparison with a s t a n d a r d t h e r m o couple. T h e cold junction was k e p t a t t h e temperat u r e of melting ice during standardization a n d during use i n measuring t e m p e r a t u r e s . F u r t h e r checks on t h e system of furnace a n d pyrometer were obtained b y placing crystals of pure diopside' in t h e positions occupied b y t h e ash cones a n d noting t h e t e m p e r a t u r e of melting; usually t h e crystal melted between 1381 a n d 139 j C. (corrected t e m p e r a t u r e readings). T h e melting point of diopside is 1391' C.* T h e Wanner pyrometer, which was originally s t a n d ardized b y t h e Reichsanstalt, was rechecked b y t h e Bureau of S t a n d a r d s after most of t h e work described in t h i s p a p e r was completed a n d found t o conform t o t h e original standardization. It was checked daily against t h e a m y l acetate flame. As t h i s pyrometer mas used only with those furnaces which h a d strongly reducing atmospheres, i t mas possible t o check t h e accuracy of t h e pyrometer readings a n d t h e blackb o d y conditions of t h e furnace b y placing t h i n strips 1 Obtained through t h e kindness of D r . Arthur L. D a y , Director of t h e Geophysical Laboratory. Arthur L. D a y and R . B. Sosman. "The hlelting Points of hlinerals in t h e Light of Recent Investigations on t h e Gas Thermometer," A m . J . Sci., [4] 31 (1911), 346.
FIG
3-ArEKER
3fUFFI.E
FURNAC NE O 29
t h e line of cones from one side of t h e muffle t o t h e other " Inasmuch a s four different was from I O t o ~ j C. cones \\-ere h e a t e d simultaneously i t was n o t possible t o begin t h e 2O-per-minute r a t e of heating at zooo
T H E J O U R N A L OF I N D C S T R I A L A N D E,VGINEERIXG C H E M I S T R Y
M a y , 19x5
belox t h e approximate softening point of each cone. Csually t h e furnace was heated up t o about 1 0 0 0 ~ C. in I hour. T h e r a t e was t h e n decreased t o z o per minute until t h e last cone had fallen, provided i t would soften in t h e possible range of t h e furnace: 1437' C. was t h e highest temperature t h a t v a s reached. and in m a n y cases, owing t o fluctuating gas pressure, 13; j o was t h e upper limit. S a t u r a l l y t h e rate of heating a t t h e higher temperatures was unavoidably reduced t o I a n d even per minute. S a t u r a l gas and air a t a pressure of about 11; pounds per square inch n e r e available. N o a t t e m p t was made t o remove reducinggases from t h e muffle by circulating air, hence, variable quantities of reducing gases undoubtedly Penetrated the magnesite muffle. -411 t h e results obtained, using two different sizes of cones, are given in Table 111. TABLE1 x 1 - C O X P A R I S O N
OF
SOFTENISC
TEMPERATURES OBTAISED
IN
NEKER MI:FFLE F U R N A C E , USINGTn-o SIZESOF COKES R a t e of heating, 2" per minute; 100 mesh ash; cones inclined 35' from t h e vertical Softening point Cone 1 Cone 7 Difference Average soften1 1 4 in. '/a in. Difference in in average ing interral X X duplicates of values of Sample l;/2in. 1 in. Cones Cone 1 C y e 2 NO. C. C. Cone 1 C o n e 2 1&2 C. C. 10 1235 ... .. .... 115 1239 11 ... .... , . ... .... .. .... ... 1323 ...
.
...
Dental Company burner, using natural gas and compressed air. T h e operation of this furnace u-as similar t o t h a t of t h e Xleker muffle furnace. t h e front being closed by a door of asbestos board with a slit in i t for t h e thermocouple. T h e essential difference between this furnace a n d t h e LIeker furnace was in t h e size and t e s ture of t h e muffle, i t being larger: 8 inches long, 4 inches wide, and 3 inches high. .Us0 the fireclay, being quite porous, permitted easier penetration of the furnace gases t h a n t h e dense magnesite muffle of the l i e k e r furnace. TABLEIV-COMPARISON
....
1281
14
15
16
. . .
....
18
1
1273 1403 1431 ~
1417 1200 1171
....
....
-
..
50
.. ..
.... .... .... ....
. , .
133
48
..
. . .
...
28
..
: 6
... ...
..
..
....
li
...
2
13
-
1212 1190 1174
-
1242 1271 1306
1187 1223 1185
...
121
10
1237
49
11
....
...
, . .
...
...
...
... 68
... ...
~
-
-
1289 1164 1303
1204
, . .
....
....
1234 1265
16
..
..,.
38
i 8 5
...
..
....
.,.
...
..
io ..
44
....
... ...
....
77
...
1310
..
35
139
iioo
....
..
60
74
...
... ...
-40
....
24
... 96
....
...
...
,..
....
34
...
... 57
I . .
38
... , . .
...
13
. .
~
5 6 8
iiii
1305 1376 ( a )
. . .
1350 1336
... ...
+12
....
220
...
14
..
+ii ....
...
,..
,..
..
~
0
....
.. ..
...
....
1437 135;
..
' 8
...
. .
45
... ... 46
...
1343 1309 1327
...
18
+17
'35
220
1318
...
..
.... -
... -
~ -
. . . . . . . . . 55
23
+46
92
60
1335
....
...
...
~
Average
-
....
... ... ... ...
...
12
1192 1226 1320 1320 1316
....
....
...
~
....
.... ....
...
54
.... 1276
8 9
... ...
29
1225 1278 1206
15i 19;
....
...
4
.. .. ..
1186 1213 1211
1307 1233 1216
I7
1298 1248
.... ....
....
12
... ... ... ... ... ... ... ...
....
1255
. 1406
SOFTESISG TEMPISRATURZS O B T A I N E D U S I N G '!?>TO S I Z E S OF C O N E S
IN
R a t e of heating, 2 0 per m i n u t e ; 100 mesh ash; cones inciitied 35O from t h e 7-rrtical lverage SOFTSNIXC POINT Difference DiffFrence soitening Cone 1 Cone 2 in in interral Sample 1rin.X 1 i n . 1 , i n . X 1 1 ?in. duplicates aversye Cone 2 so. c. C. of Cone 2 value> O C. 1 .... 1195 .. .... .. .... 1189 , . .... , .
~
12 13
OF
MUFFLEFURNACE h-0. 2 ,
I
..
403
1318 ....
1251 1242 1325
....
6
....
..
i-50
.. ..
....
..
.... ....
38 19 73
...
...
4
. ... .
1.53 ...
..
.... ....
... ...
..
..
....
94
1284 1212 1186
83
....
....
....
85
....
..
1199 1212 1215
26
.. ..
+38
..3..8..
1214 1195 1168
3
..
i 5 2
....
..
....
1182
27 -
.... .... -
....
....
....
-
1268
.... .... ....
....
....
..
~
....
34
... ... 135 -
.................... 25 +47 74 9 s shou-n in Table IT t h e average softening intervals, differences in average values of Cones I and 2 , and differences in duplicates, are practically t h e same a s those obtained in t h e l l e k e r furnace. However, a striking difference is shown on comparing the softening points of those samples which were r u n in both furnaces, under apparently t h e same conditions; with Average..
TABLEV-COXPARISON OF SOFTENIKG TEMPERATURES OBTAINED IN ~ I E K E FURNACE R AND MVFFLEFURNACS No. 2 R a t e of heating, 2' per minute; 100 mesh ash; cones inclined 3 j 0 from t h e vertical SOBTENING - POINT - . ~.. Muffle furnace Meker Sample Size of cone No. 2 furnace No. Inches * c. c. Difference 4 1;4 x 1112 1226 1310 -84 5 1:4 x 11;2 1320 1376 --56 1343(a) --92 1251 8 ' 1 4 x 1'12 1318(a) --34 1284(a) 9 1 1 4 x 11;* 10 114 x 1 1237 1235 T 2 11 114 x 1 1268 1281(0) --I3 -Average, - 4 6
' a ) Averace oi t n o determinations.
T h e ' / 4 inch by I~,'? inch cone gave more definite indications of softening t h a n t h e inch by I inch cone as shown bx t h e smaller softening interval (temperature range from initial t o final deformation) a n d smaller differences in duplicate determinations. T h e softening points of t h e taller cone average 46' less. as would be expected on account of t h e greater bending moment.
b u t one exception t h e results of t h e muffle furnace S o . z are from 13 t o 9 2 ' lower t h a n those of t h e 1Ieker furnace. t h e aL-erage difference as given in Table Tbeing 4.6'. (This difference is belie\-ed t o be due t o n greater reduction t o ferrous iron due t o t h e greater penetration of reducing-furn::ce gases through thc walls of the porous fireclay muffle t h a n through t h e denser magnesite muffle of the bleker furnace.) Both furnaces were usually operated with some flame appearing :>t the Lbininc> since it m a s only hy this method of adjusting gas and air t h a t the higher temperaI
B-NUFFLE
PURXACE S O
2
This f u r n x e w a s a fireclay assay muffle set in a chamber made ot firebrick and heated b y a Buffalo
T H E J O C R N A L OF I l V D C S T R I A L A N D ENGINEERI;VG C H E M I S T R Y
404 1500
y
'400
0 I-
H
l3O0
z
z
v01. 7 ,
KO. 5
tween the exactly centered alundum tubes. After I O or ~j runs, heating became irregular, due t o oxidation of t h e resistor, which then necessitated repacking the resistor and sometimes renewal of the alundum tubes. I n view of these difficulties, the interior of the furnace deviated somewhat from black-body conditions, which introduced a n error in the absolute values of t h e temperature measurements. Observations of the melting points of copper and nickel indicated t h a t this error was usually less t h a n 30' a t the copper point. and less t h a n j o o C. a t t h e nickel point. All the softening temperatures determined in t h e carbon resistance furnace are given in Table VI. The rate of heating, fineness of ash, size and inclination of cone were t h e same a s in the preceding series. T h e I
1200
51 10
11
4
9
5
8
15
13
18
17
16
ASH NUMBER
FIG.
OF SOFTENING TEMPERATURES OBTAINEDI N MEHER FURNACE A N D MUFFLEFURNACE No. 2
4-COMPARISON
tures could be attained a t the desired rate of heating.
As a matter of fact, t h e gray appearance of t h e base material, in which t h e cone was mounted, in many of t h e tests was in itself an evidence of reduction, since when heated under strictly oxidizing conditions i t took on a slight reddish tint. The marked lowering of softening temperature b y partial reduction is shown graphically in Fig. 4, where the muffle and hIeker furnace results are compared with those obtained on the same ashes in a platinumresistance f u r n a c e . Obviously n; reduction could t a k e place in t h e electric furnace. Differences of over 200' C. were found in some cones. C-CARBON
RESISTANCE
FURXACE
On account of ease of construction and ability t o attain high temperatures, various forms of granular carbon, graphite, or kryptol resistance furnaces are often used f o r determining t h e softening temperatures of refractory materials.' -i A furnace of this t y p e was built as shown in 'C Fig. j . The resistor or FIG.5-Carbon resistance furnace: b, fireclay cylinder, 8 inches external diam- heating element was t h e eter, I O inches high, I-inch wall; d, fire- 1,l4 inch thick annular I-i
clay cover plate, 2 inches thick; m. fire- . clay plate covering peep-hole; f,alundum ring Of granular carbon, tube, 3-inch bore, 4 inches long, 5/16- a , between t h e two inch wall; e, alundum tube, 2-inch bore, concentric a1 d 9 inches long, l/r-inch wall; a, granular carbon resistor consisting of electrode tubes e and .f. This carbon crushed t o pass a 6-mesh a n d re- heating. zone was 4 main on a 12-mesh screen; i , i , wrought- . inches high. The curiron electrodes; 0 , granular carbon; $, magnesia insulating material; I, inverted rent of 2 0 t o jo amperes alundum crucible; h. ash cone. was regulated with a
-
water rheostat, the temperature being measured with a Wanner optical pyrometer. A uniform heating zone was obtained by carefully packing the carbon be1 A. V, Bleininger and G. H. Brown, "The Testing of Clay Refractories, etc.," Technologic Paper X o . 7, Bureau of Standards, 1911, p. 14; Zay Jeffries "Notes on the Gran-Annular Electric Furnace," Met. and Chem. Eng., 12 (1914). 154-157.
b5M
NUMBER
FIG. COMPARISON OF SOFTENING TEMPERATURES OBTAINEDIN THB CARBONRESISTANCEFURNACE, MEKER FURNACE AND MUFFLE FURNACE h'o. 2
essential difference was a reducing atmosphere of carbon monoxide which reduced the ferric oxide of t h e ash more or less completely t o metallic iron. Consequently, the softening points obtained bear little relation t o TABLE VI-COMPARISON
OF SOFTENIHG TEMPERATURES OBTAINEDIN THE CARBONRESISTANCEFURNACE, USING T W O SIZES OP CONES R a t e of heating, 2' per minlite; I00 mesh ash; cones inclined 3 5 " from vertical
.- g*
K W N
SOFTENING POINT I N 7
C. F
e: *
2
I -
- E + C
Maximum d difference E > of deter- 0 & minations Eo
2 E
m
UG
o n:
Cone 1 Cone 2 e, l/i in. X 1 in. '/a in. X 11,'s in. XI.- Y Individual Individual Y U E w g Ash determina- AverdeterminaAver- Cone Cone;; 2 % $.zO IL-0. tions age tions age 1 2 e 8 1 I100 . . . . . . . . 1100 1076 1 I O 4 , . , . 1090 . . . . . . . . + I 0 88 68 f 3 8 53 2 1675 1.587 . . . . 1631 1587 1562 1630 1593 . , . . 1562 25 . . . . -4 . . . 1562 1558 1570 1545 . . . . 3 1335 1241 1494 1357 1182 i i i j 1210 . . . . 253 . . . . . . . . . . . . . . . . . . . . . . . . . . . 1210 1480 1540 1306 . . . . 358 + 5 l 70 1331 l 3 i 1 1500 1401 1259 1263 1402 . . . . . . . . . 1502 . . . . . . . . 1356 ,.. .... . . . . 1179 1260 1161 i i$S 12Oi 1179 1630 1695 . . . . 1663 1645 i636 , , , , 1638 1I92 I I64 1167 , , . , 1166 1185 1I99 1365 1 2 7 1 ijis 1327 1245 1 2 i l 1230 1249 10 1185 1188 . . . . 1187 1161 I l i 3 . , , , 116; 11 1133 1206 . . . . 1190 1 1 2 3 11.55 , . . , 1139 1088 12 1084 1092 . . . . 1088 1088 1088 i 3 1. 3. 1322 13 1380 1400 . . . . 1390 1322 1331 142; . . . . 1424 1420 1520 14 I520 1520 . . . . I5 1322 1300 . . . . 1311 1 2 i 4 1 2 4 1 1134 1250 16 1402 1385 . . . . 1394 1350 1331 . . , , 1341 l i 1267 1234 . . . . 1251 1241 1210 1210 1220 18 1331 1300 . . . . 1316 1241 1255 1255 1250 Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average, excluding 4 and 5 , . . . . . . . . . . . . . . . .
+5i
+3i
+58
t23
+41
64
those obtained subsequently in air as shown b y comparison with t h e platinum-furnsce series in Fig. 8 ; with but one or tm-o exceptions t h e results are considerably 1on:er ( I j o t o z j o o C , ) . X closer relation is shown between the carbon-furnace series and t h e t v o muffle-furnace series as plotted in Fig. 6 . -4s in the muffle- and Lleker-furnace tests, the ' 1 4 inch b y rl/, inch cone softened a t from I O t o 90' lower in temperature t h a n t h e '/1 inch b y I inch cone, t h e average difference being 41' and t h e former
RIay, 191j
T H E J O L - R S d L OF I n ' D C S T R I d L A N D E S G I N E E R I S G C H E M I S T R Y
cone giving better duplication. T h e average softening intervals a n d t h e average differences in duplicates of Cone z were practically t h e same as in t h e gas furnaces. D-KORTHRUP
PURKACE
T h e Northrup high-temperature electric furnace' 2 has a cylindrical heater unit of Acheson graphite which is surrounded b y a refractory cylinder a n d non-conducting material. T h e whole is enclosed in a n air-tight monel-metal jacket. Carbon monoxide is formed b y t h e oxidation of a thinwalled graphite cylinder which fits snugly within t h e heater u n i t ; this reducing atmosphere protects t h e resistor from rapid oxidation. Fig. 7 is a vertical section through t h e heater unit with t h e ash cone in FIG.i-Arrangement f o r softening-temperature test in X o r t h r u p furnace: f. graphite heater position for testunit; b , graphite t u b e f o r protecting heater ing. f r o m oxidation, 1-518" internal diameter, lP/d T~~~~ a e inches long; e. solid graphite cylinder, 2 inches high, d inverted a l u n d u m extraction capsule, 3 inches high: a , a refractory plug: i,i,observation holes, 1/4 inch diameter
ea e ents were made with a Wanner optical pyrometer which was sighted directly on t h e cone a n d its base through t h e peep-hole i in t h e center of t h e cover plug a. T h e degree of accuracy of t h e temperature measurements is shown b y t h e following melting points of copper a n d nickel obtained under test conditions: Apparent Apparent K a h l b a u m ' s pure copper melting Kahlbaum's pure nickel melting M. P. = 1083' C . ( a ) point hI p. = 1450' C . ( a ) point July 10, 1914 . . . . . . . . . . . . 1088 July 11, 1914 . . . . . . . . . . 1448 July 14, 1914 . . . . . . . . . . . . 1088 July 22. 1914. . . . . . . . . . 1455 July 2 i , 1914.. . . . . . . . . . . 1096 July 2 i , 1 9 1 4 . . . . . . . . . . 144; .!lug. 13, 1914. . . . . . . . . . . 1088 l a ) Provisional temperature scale used by Bureau of Standards.
X change of procedure was niade in t h e S o r t h r u p furnace series, in t h a t t h e ash was ground t o an impalpable powder a n d molded into a 1 8 inch b y I inch cone which was mounted vertically. It will be shown hereinafter in t h e discussion of t h e tests made in t h e molybdenum a n d platinum furnaces t h a t the difference in softening points due t o changing these factors is small. usually less t h a n 3 0 ' . a n d , therefore, not sufficientto iiiateriallyaffect t h e comparison of the S o r t h r u p furnace series with t h e other furnace series. t o show t h e influence of different atmospheres. 1 E. F. S o r t h r u p . "A S e w High-Temperdture Electric Furnace," M e t . and Cliem. l i n g . , 12, 31.
405
Since both t h e Northrup a n d granular-carbon resistance furnace produced atmospheres of carbon monoxide, similar softening temperatures were expected in t h e t w o series; t h a t such did n o t prove t o be t h e case is shou-n in Table 1-11 and Fig. 8. I n 16 of 18 samples tested, t h e softening points in t h e Xorthrup furnace were higher t h a n in t h e carbon furnace; t h e maximum was 396' a n d t h e average difference for t h e series was 134'. T h e check made on materials of known melting points, a t various times during t h e course of these experiments, effectually rule out t h e possibility of attributing these large differences t o errors of temperat u r e measurement. T h e only explanation we have t o offer is t h a t in t h e carbon furnace t h e reduction of ferric oxide t o metallic iron did not proceed a s rapidly or as completely as in t h e Northrup furnace; in the TABLEV I I - C O M P A R I S O K
OF
SOFTEhIKG
TEMPERATURES OBTAIhED
IN
NORTHRLP GRAPHITERESISTANCE FURNACE WITH THOSE OBTAINED I N CARBON RESISTAKCE FURNACE
Reducing atmosphere of carbon monoxide, r a t e of heating, 2' per minute Softening point in C. Softening interval, in C Ash Northrup(a) Carbon@) Northrup Carbon No furnace furnace Difference furnace furnace 1 1090 67 8 1131 t 41 1593 167 53 1645 52 1502 1562 - 60 100 ... 1360 1306 181 70 54 1645 1356 30 121 +289 4-275 18 I179 1455 355 70 1645 1638 75 1166 +396 56 1562 392 51 +I91 1249 9 70 1440 10 1218 1167 i2 31 1385 11 46 1185 1139 85 24 - 8 1088 12 16 30 1080 1322 198 13 129 1520 18 1424 14 2; 124 136 1551 1250 1427 t177 140 15 83 1341 16 1470 4-129 48 94 li 1220 +liO 1390 95 39 1250 18 1455 +205 124 83
+ + + ,
+
B
+ ++
-
~
(a)
vertical (b) average
-
Average, +134 120 64 Ash ground to a n impalpable powder; 3/18 inch by 1 inch cones in position. Single determinations only. 100 mesh ash; inch by l!/, inch cones inclined 35' from vertical; of t w o or more determinations in most cases.
latter furnace t h e ash cone is heated in a closed t u b e of graphite which excludes practically all air circulation so t h a t only nitrogen, C O , a n d a fractional per
1105
RaniF.,D,*
FIG
U
W
I4
P
IO
9
7
70
9
II
5
8
7
.
.
$0
10
I
10
8-COMPARISON OF S O F T E N I N G T E M P E R A T U R E S O B T A I N E D I N S O R T H RCP C A R B O N RESISTANCE AKD P L A T I K U M F C R N A C E S
cent of CO1 mould surround t h e ash a t temperatures above 1100'. Such a n atmosphere would reduce the ferric oxide t o metallic iron a n d t h u s prevent t h e formation of a low melting ferrous silicate eutectic. On t h e other h a n d , t h e carbon furnace permitted air t o leak into t h e heating space as shon-n b y t h e appearance of carbon monoxide flames a t t h e peep-hole a n d arouqd the cover-plate. Sufficient carbon dioxide m a y , therefore, have been present t o retard t h e reduction t o metallic iron. t h u s leaving enough of t h e strongly fluxing ferrous oxide in the ash t o form a low-melting fluid
406
T H E J O C R i V A L O F I N D U S T R I A L A N D EXG14VEERIiVG C H E M I S T R Y
eutectic which caused t h e cone t o collapse a t a comparatively low t e m p e r a t u r e . ExBmination of polished sections of fused cones f r o m b o t h furnaces disclosed more metallic iron i n those from t h e N o r t h r u p furnace. (Tobe concluded in June issue) BUREAUOF MINES,PITTSBURGH, PA.
PRACTICAL METHODS FOR THE DETERMINATION OF RADIUM‘ I-INTERCHANGEABLE ELECTROSCOPE AND ITS USE By S. C. LIND Received January 4, 1915
T h e interest i n radium-bearing ores a n d other radioactive p r o d u c t s intermediate between ores a n d highgrade r a d i u m s a l t s h a s become so general t h a t t h e q u a n t i t a t i v e determination of r a d i u m has ceased t o be a problem exclusively of t h e physicist or t h e radioactivitist. T h e t i m e a p p e a r s t o h a v e come when a n y good analyst or assayer should be prepared t o make r a d i u m determinations, a n d i t is t h e object of t h i s p a p e r t o describe a modified form of electroscope a s well a s some methods which i t is hoped m a y prove useful i n t h i s direction. T h e “ e m a n a t i o n -method,” which will he fully described in P a r t 11 of t h i s p a p e r , is recognized as t h e most accurate method for determining r a d i u m in small quantities. T h e t w o difficulties against its general employm e n t are a t present t h e t i m e required a n d t h e expense of t h e necessary a p p a r a t u s . T o o b t a i n t h e highest degree of accuracy with present methods, accumulat i o n of e m a n a t i o n i n a closed volume for a m o n t h is required i n m a n y instances t o insure t h a t t h e q u a n t i t y of e m a n a t i o n is proportional t o t h e r a d i u m content. This delay of one m o n t h i n obtaining t h e results is for practical purposes almost prohibitive.’ F u r t h e r m o r e , only one determination per d a y can be conveniently carried o u t with one electroscope, so t h a t in a laboratory where a n u m b e r of daily determinations are t o be made t h e initial expense for electroscopes becomes excessive. T o overcome this l a t t e r difficulty a n electroscope of simple construction has been devised. All of i t s p a r t s except t h e telescope can be m a d e b y a n y mechanic. Its chief a d v a n t a g e lies, however, in t h e fact t h a t i t is constructed i n two easily detachable p a r t s ; t h e upper p a r t , consisting of t h e telescope a n d leaf s y s t e m , m a y be transferred t o a n y n u m b e r of separate discharge chambers. T h e l a t t e r are inexpensive a n d hence t h e interchangeable t o p permits one t o employ a n y desired n u m b e r of i n s t r u m e n t s with little additional expense. X e t h o d s of shortening t h e time required for a n analysis t o a few days without sacrificing accuracy can also b e a t t a i n e d a n d will be described with examples i n a second paper. T h e classes of substances which one h a s t o analyze f o r r a d i u m , are, i n America, chiefly t h e u r a n i u m ores, c a r n o t i t e a n d pitchblende, a n d t h e crude radiumb a r i u m sulfates or chlorides of varying degrees of concentration of r a d i u m . T h e practice u p t o t h e present with respect t o ores has been t o estimate t h e r a d i u m from t h e uranium content, while buying 1
Published with permission of t h e Director of t h e Bureau of Mines.
2
For further discussion see paper t o follow.
Vol. 7, No. 5
a n d selling exclusively o n t h e l a t t e r . Whatever unc e r t a i n t y m a y h a v e been involved, due t o t h e supposed variability of t h e R a / U ratio i n carnotites a p pears t o h a v e been removed b y ’ t h e recent establishm e n t of i t s constancy a t normal value.‘ T h i s would appear t o justify more t h a n ever t h e existing practice, b u t , o n t h e other h a n d , i t is incontestable t h a t t h e accurate determination of u r a n i u m is difficult a n d time-consuming. I t is t h e author’s opinion t h a t r a d i u m can be determined directly with more accuracy t h a n u r a n i u m , a n d hence i t is recommended t o replace t h e u r a n i u m determination b y a direct electroscopic measurement of r a d i u m b y t h e emanation method. Of course i n dealing with a n y ore in which uranium has been removed or added, or t h e R a / U ratio i n a n y
FIG.
1
nray disturbed, i t becomcs essential t o determine r a d i u m directly. This applies also t o crude sulfate or chloride, or a n y kind of mill products, a n d t o a n y ore suspected of addition of u r a n i u m , or t o one from which r a d i u m h a s been wholly or p a r t l y removed. or t o a n y sample of ore t o n-hich a spurious addition of r a d i u m has been made. It m a y also be mentioned t h a t t h e failure of m a n y a t t e m p t s t o extract r a d i u m profitably on a commercial scale m a y be a t t r i b u t e d in most cases t o t h e neg1
Lind and Whitternore, J . A m . Chem. SOC, 36 (1914). 2066.
