T H E J O U R N A L OF I N D U S T I U A L A N D ENGINEERING C H E M I S T R Y
438
methods of handling t h e product throughout are of t h e greatest importance. If properly prepared, t h e sodalime should absorb in t h e neighborhood of 0.3 g. of carbon dioxide per gram of soda-lime at high rates of flow before its efficiency drops off seriously. I t is reasonably hard, granular, and non-deliquescent. T h e material possesses a further great advantage over t h e ordinary high caustic-absorbing materials for respirators in t h a t it gives off much less heat due t o t h e fact t h a t it evaporates off rather t h a n absorbs moisture. The suggestions made in this section as t o t h e modifications of the a r m y soda-lime for industrial purposes are based on investigations which are as yet incomplete. T h a t t h e recommended procedure will produce an absorbent several times as efficient as any soda-lime now on t h e market has been verified by thoroughgoing tests on all available commercial soda-limes. It should have considerable value for use in steel analyses, where present types of soda-lime do not give satisfactory service, and for other industrial purposes. RESEARCH DIVISION,C. W. S., U. S. A. AMERICANUNIVERSITY EXPERIMENT STATION WASHINGTON, D. C.
EFFECT OF EXPOSURE TO WEATHER ON RUBBER GAS MASK FABRICS' By G. ST. J. PERROTT AND A. E. PLUMB Received March 18, 1919
The purpose of this investigation was t o determine t h e relative desirability for gas mask use of a number of rubber coated fabrics submitted by different rnanufacturers, particularly with regard t o their resistance t o t h e deteriorating effect of exposure t o t h e elements. The desirable qualities in a rubber fabric for gas mask use are: 1-Resistivity to war gases 2-Flexibility and comparative lightness 3-Resistance to deterioration by weather 4-Resistance to deterioration due to exposure to gas
Vol.
11,
No. 5
ing roof with southern exposure. At successive periods samples were cut t o be examined for permeability, acetone extract, and general physical properties.
Acefone Ewtrac+ Per cent.
FIG. I-FABRICS
EXPOSED TO WEATHER, FEBRUARY TO JUNE,
1918.
ACETONE EXTRACT
At t h e time when t h e investigation was started (early in February) it was thought t h a t exposing samples in Florida would give quicker deterioration due t o greater amount of heat, sunshine, and moisture. Accordingly, Samples P-198, P-199, P-197, and P-205 were exposed in Florida. Later other samples were exposed in Washington, of which P-197 and P-200 are duplicates of P-198 and P-199, respectively. I n order t o determine t h e effect of ultraviolet light in t h e sun's rays on t h e rate of deterioration, a portion of each fabric exposed was covered with a sheet of glass in. thick. This shielded t h e fabric underneath from t h a t portion of the sunlight which is of short wave length.
MATERIALS U S E D
Gas mask fabrics consisting of a finely woven cotton sheeting covered with a rubber layer varying from 0 . 0 1 0 to 3 . 0 2 5 in. in thickness were used for t h e tests. FABRIC No. P-190 P-196 P-197 P-198 P-298 P-199 P-200 P-299 P-205 P-366 P-297
Weight Manufacturer Oz./Sa . - Yd 29.06 Plymouth Co. 18.9 U. S. Rubber Co. 15.0 Kenyon Co. 13.9 Kenyon Co. 15.4 Kenyon Co. 19.1 Goodrich Co. 15.3 Goodrich Co. 15.5 Goodrich Co. 16.0 Goodyear Co. 13.8 Goodyear Co. Plymouth Co. 15.9
Thickness of Rubber Layer Inch 0.025
0.015 0.012 0.011 0.011 0.018
0.016 0.012 0.019 0.012 0.010
Date Received Jan. 16, 1918 Jan. 21, 1918 Jan. 21, 1918 Jan. 21, 1918 April 19, 1918 Jan. 21, 1918 Jan. 21, 1918 April 19 1918 Feb. 14: 1918 May 13, 1918 April 19, 1918
METHOD O F EXPOSURE
The effe-t of exposure t o weather (sun and rain) and the effect of exposure t o heat alone have been investigated. For exposure to weather, t h e samples were loosely stretched on wooden frames placed on a slightly slop1 Approved for publication by the Director of the Chemical Warfare Service.
FIG.2-FABRICSEXPOSED TO
WEATHER,
FEBRUARY TO JUNE, 1918.
PERMEABILITY
The early samples were exposed rubber side up. Surface cracking occurred so quickly t h a t later tests conducted in Washington were run with samples both rubber up and cloth up. The accelerated aging tests were made in a Freas electric drying oven, heated t o 130' C., well ventilated by an electric fan. Temperature did not vary more t h a n a few degrees in any part of t h e oven. No attempt was made t o control humidity. Samples were cut a t successive intervals over a period of 18 hrs.
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
M a y , 1919
TAB&& I
FABRICS EXPOSED IN FLORIDA, FEBRUARY-JUNE 1918 Days Aged 0 11 25 ..... 32 57 77 89.. 100 114.
..... .....
..... ..... ..... ... .....
Minute6 t o Penetration against Chlorpicrin (Saturated Vapor a t 20° C.) PPPP196 198 199 205 35 19 28 34 30 42 50 30 25 44 45 30 20 .. 46 30 21 50 46 30 2 39 45 23 Dis39 23 15 con26 26 15 tinued 17 16
Per cent Acetone Extract PPPP196 198 199 205 5.8 4.4 7.3 5.4 16.6 3.5 6.9 5.5 13.4 5.3 9.2 5.8 23.9 5.7 8.0 6.0 34.7 6.5 8.0 5.7 38.5 6.4 7.4 5.6 Dis7.7 6.2 con9.0 tinued
... ... ......
.......
FABRICS EXPOSED IN WASHINGTON, FEBRUARY-JUNE, 1918 Per cent Acetone Extract Days PPPAged 190 197 200 0. 4.7 2.5 42 12.7 6.3 3.1 52 12.8 20.5 4.5 66..... 13.4 24.4 80 14.0 28.6 6.7 Discon7.1 97... 13.4 112. tinued
...
...
439
....... ..... ..... .. ........
.....
..
...
Minutes of Penetration against Chlorpicrin (Saturated Vapor at 20' C.) PPP190 197 200 92 18 30 25 30 97 7 12 96 9 14 83 Z/I 14 87 Discon13 82 tinued 13
..
TABL 11-FABRICS ~ EXPOSED I N WASHINGTON MAY25 1918-AUGUST 2 1918, SHOWING EFFECT OF EXPOSINQ RUBBERSIDE AND CLOTH SIDE OF FABRICS ~b SUN A ~ DOP SHIELD IN^ FABRIC FROM ULTRAV~OLET LIGHT -P-297-
-3.7 f m
-Minutes
Per cent Acetone Extract-P-298-P-299m - 3
-P-366-
P
g
5.3 5.3 6.5 4.9 5.8 5.5 5.6 6.4
5.3 4.4 6.9 6.4 6.6
rP
t o Penetration against Chlorpicrin Vapor(Saturated a t 20' C.) cP-298CP-299--P-366-
cP-297-
Days Aged
1.7 .. ... ... 2 . 8 14.. . ... 3 . 8 21.. , ... 3 . 7 28.. . ... 4 . 4 42.. . ... 5 . 5 56.. . ... 7.5 70.. . ...10.1
0.. 7..
1.7 2.5 3.8 2.2 2.2 2.2 2.5 3.5
1.7 2.1 3.4 4.4 4.2
...
... ...
3.9 5.7 5.8 10.1 12.7 18.2 22.2 27.2
3.9 3.9 5.8 4.1 5.0 5 . 3 5.7 9 . 4 6.2 11.0 7.1 8.1 8.7
... ... ...
5.3 4.4 7.0 6.7 6.5 7.7 9.2 11.7
5.3 4.4 5.9 4.9 6.9 4.8 4.7 6.0
5.3 4.4 5.1 7.2 7.2
... ...
...
5.3 5.2 6.2 6.2 6.8 6.6 7.2 8.2
I t is important t h a t a rubber fabric for gas mask use should not deteriorate from exposure t o gas. T o determine t h e amount of deterioration, several fabrics were exposed in t h e man-house chamber t o varying concentrations of chlorpicrin a n d phosgene for several days, t h e fabrics being examined a t intervals. TESTS MADE Of t h e fabrics was determined in a specially designed apparatus.' A 4-in. square of t h e fabric is clamped in a horizontal position in a cell which i t divides into two compartments. T h e lower compartment contains a cotton pad saturated with chlorpicrin. The apparatus is immersed in a b a t h a t 2 0 ° C. A current of air is drawn over t h e t o p of t h e fabric, through a silica tube heated t o about 400' C., into a starch-potassium iodide solution. The first trace of chlorpicrin diffusing through t h e fabric is indicated b y t h e appearance of a blue color. The time from t h e beginning of t h e tests t o t h e appearance of t h e blue color is called t h e time t o penetration. After exposure tests had proceeded for a few weeks, an increase in t h e hardness and brittleness of t h e rubber layer which rendered i t susceptible t o cracking was noticed. I n order t o detect this brittleness, a folding test was devised. The ends of a strip of fabric were gripped by two wide clamps. A lead weight was suspended from one of these, a n d with t h e other clamp t h e fabric was drawn over a steel straight edge a t a n angle of 90' back a n d forth I O times under a tension of I lb. per linear in. The permeability was determined after t h e fabric had been folded in this manner. This precaution obviated misleading results due t o stiffening of t h e fabric. A C E T O N E EXTRACT-Rubber, both crude and vulcanized, is insoluble in acetone. When rubber breaks down through aging, oxidation, etc., t h e decomposition products are soluble in acetone. This test is therefore one indication of t h e life of rubber goods; a
PERMEABILITY-permeability
1 A more detailed fabrics will be given in
JOURNAL.
... ... .,.
15
15
15
ii io is 7 7 3 2 1
7 11 8 10
16 16
..
..
....
20
25
25
i o ii is
20
ii
3; 13 18 19, 20 17 . . 15 . . 14 . .
21 14 16 4 3
20 17 19 22 17 11
25 26
.. .. ..
17 13 15 11 7
25
21
ii
ii ii ii
24 6 6 7 2
21 24 12 12 21 19
21
..2 .._ ...
slight increase in acetone extract from time t o time would show normal aging, while a rapid increase would indicate t h a t t h e life of t h e material was a t a n end. Acetone extractions were made on 2-g. samples in a battery of 9 Wyley extractors for a period of 8 hrs. The solution was then transferred t o a weighed, 150-cc. flask, t h e solvent evaporated on a steam bath, using a gentle current of air, dried t o constant weight in a drying oven a t 9 j O C., and weighed. T h e extract was corrected for free sulfur. Free sulfur was determined by adding 40 t o 60 cc. These were alof water and 2 or 3, cc. of bromine. lowed t o digest on the water bath until t h e solution was nearly colorless, then filtered a n d washed. The sulfur was precipitated as barium sulfate a n d calculated t o sulfur.
Ace tone Extrac f -Pe; cen i7 F I G . 3-FABRICS
EXPOSED TO WEATHER, WASHINGTON, MAY 2.5 AUGUST2, 1918. ACETONEEXTRACT
TO
DISCUSSION
Consideration of curves shows that, with the exception of fabrics from t h e Kenyon Company, all samples deteriorated a t about t h e same rate. Fabrics description of methods of testing permeability of aged in Florida and Washington this winter showed a n article by one of us in a future number of THIS no marked increase in acetone extract over a period
440
T H E J O U R N A L OF INDUSTRIAL A N D ENGINEERING C H E M I S T R Y
Vol.
11,
NO.
j
general trend of each curve was considered, and percentage increase or decrease calculated. The fourth column, based on t h e other three, is to some extent a question of judgment. It is apparent, however, t h a t P-196 and P-zoo are best, and P-197 and P-198 poorest. TABLE111-RELATIVE DESIRAIIILITY Time to Penetration
Minutes to Penetration -G-Z5 P I G . 4-pABRICS
EXPOSED TO
WEATHER,
AUGUST2, 1318.
W A S H I N G T O N , MAY
25
TO
PERMEABILITY
of I O O days. The difference in temperature between Florida and Washington did not prove t o be sufficient t o markedly change t h e rate of deterioration. Deterioration in physical appearance had noticeably taken place on all t h e fabrics after one month. The surface became covered with minute cracks which, as time went on, deepened. The Kenyon fabrics (P-197 and P-198) were covered with deep cracks after 6 weeks, and became gummy and quite useless. Of t h e other fabrics, P-196 retained its original flexibility through the entire I O O days. From inspection of Fig. z it is apparent t h a t resistance t o penetration by chlorpicrin increased for t h e first month and then declined. This is evidently due t o t h e increased resinification of t h e rubber (as indicated by increase of acetone extract), making a harder surface less easily penetrated by chlorpicrin. Later, although t h e amount of resin still increased, brittleness and checking of t h e rubber film reduced t h e thickness of rubber effective as a buffer t o the gas. Four samples last received (P-297, P-298, P-299, a n d P-266) were exposed in Washington for a period of I O weeks, May z j t o August 2 . One-half of each sample was exposed with t h e rubber side up and onehalf with cloth side up. A small part of each sample was covered with glass t o exclude ultraviolet light. The samples in which t h e rubber was exposed t o t h e sunlight deteriorated much more rapidly t h a n the samples shielded by t h e cloth backing of the fabric. Acetone extracts and cracking of t h e surface increased much more rapidly t h a n for t h e sa.mple exposed during t h e winter months. At t h e end of I O weeks, increase in permeability, in acetone extract, and in poor appearance, was very marked. I n contrast, t h e samples aged rubber side down were well preserved. The fabric weathered under glass did not differ markedly in properties from t h a t exposed t o t h e full rays of t h e sun. Fabrics have been arranged in Table I11 according t o their efficiency, which is based on permeability t o chlorpicrin, acetone extract, and appearance. The
Acetone Extract P-196 P-205 P-190 P-366 P-299 P-199 P-200 P-297 P-298 P-197 P-198
Appearance P-196 P-205 P-190 P-199 P-200 P-366 P-299 P-298 P-297 P-197 P-198
Averane
P-200
P- 199 ~. ~
'
P-366 P-297 P-298 P-197 P-198
There is apparently a fairly close relationship between increase in permeability and increase in acetone extract. Such a relationship is logical, since increasing acetone extract is an evidence of t h e decomposition of the rubber. ACCELERATED AGING
Rubber manufacturers in determining t h e best composition of a mix make use of an accelerated test t o determine t h e relative aging properties of different samples. I n this test t h e sample is heated in an oven and the change in properties noted a t t h e end of several hours. Our experiments showed no relation whatever between results of actual weather exposure and accelerated aging. Fabrics heated in an oven a t 70° C. for 2 0 0 hrs. showed no perceptible deterioration. A series of fabrics was run a t 130' C. and results compared with those obtained by weather aging. Acetone extracts and permeability were determined every 3 hrs. for 18 hrs. Figs. j and 6 show t h e results. Acetone extract increased for 9 hrs. and then remained stationary. Resistance t o gas increased for 9 hrs. and then decreased, due t o cracking of t h e rubber when creased. There is, however, no relation between these values and those obtained b y exposure t o weather. P-zgg stood up best against weather aging, P-298 poorest. I n t h e accelerated test, P-298 was as good as ever after 1 2 hrs. heating; P-zgg was hard and brittle. The method might have some value
FIG
5-ACCELERATED
AGING AT 130"
c
ACETONE EXTRACT
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 CHEMISTRY
klay, 1919
as a check on successive mixes of t h e same composition, b u t is apparently not dependable where a number of different samples of varying compositions and treatments are being tested. ELECTRIC DRYINGOVEN Minutes t o Penetration against Chlorpicrin Vapor (Saturated a t 25' C.) PPPP297 298 299 366 2.5 21 1.5 20 22 40 56 29 48 36 89 41 23 42 69 35 36 43 81 42 39 47 120 57 31 27 26 24
TABLE IV-ACCELERATDDACING AT 130' C.
Hours 0
3 6 9 12 15 18
,
Per cent Acetone Extract PPPP297 298 299 366 5.3 3.9 .i3 1.7 2.8 5.6 5 9 9.3 10.7 8.0 17.0 11.7 13.3 14.0 22.1 20.9 11.3 13.5 19.7 22.3
.. ..
..
..
.. ..
..
..
IN
E X P O S U R E T O GAS
ANALYSIS
I n order t o obtain, if possible, an idea of why cert a i n fabrics deteriorated more rapidly t h a n others, a chemical analysis was made of t h e samples under consideration. SPECIFIC GRAVITY was determined b y weighing a sample of stripped fabric in air and in water, using an analytical balance and a beaker of water set on a bridge over t h e balance pan. The sample was suspended from t h e beam b y a hair. THICKNESS was determined b y an Ashcraft microgauge reading t o thousandths of an inch. Thickness as here given is t h e thickness of t h e rubber coating of t h e fabric. ASH was found b y igniting a one-gram sample a t t h e lowest possible heat and weighing. The ash was t h e n used for t h e inorganic analysis. MATTER INSOLUBLE IN HC1 was found by boiling with I : I hydrochloric acid, filtering, washing, and weighing. CALCIUM,
P E T R O L E U M W A X was determined by charring an acetone extraction with 2 or 3 cc. of concentrated sulfuric acid, neutralizing with alcoholic potash, extracting with petroleum ether, evaporating in a weighed flask, and weighing.
18
/5 /2
9
6 I33
It is important t h a t a gas mask fabric should not deteriorate from exposure t o gas. To determine t o what extent t h e fabrics under consideration were affected b y such exposures, they were left in a gas chamber containing a concentration of phosgene of 10,000 p . p . m. for I j hrs. Other samples of t h e fabkics were exposed for 1 5 hrs. t o a concentration of 2,000 p. p. m. of chlorpicrin. The cloth backing of all t h e fabrics was rotted by both gases. The rubber of P-196 was unaffected b y either gas. Phosgene deteriorated t h e rubber of t h e other fabrics. Chlorpicrin caused deterioration of t h e rubber of P-298, but not t o so great a n extent as phosgene. Apparently t h e high percentage of carbon i n P-196 protected it against t h e action of t h e gas ,(see Table V).
LEAD, IRON, ALUMINUM,
44 1
AND
MAGNESIUM
were determined gravimetrically. Zinc was titrated with standard potassium ferrocyanide ( 2 2 g. per l.), using uranyl nitrate indicator. A C E T O N E E X T R A C T S were made as already described. Following this, a chloroform extraction was made on t h e same 2 g. sample for bitumen, asphalt, coal tar, pitch, etc. BITUMEN was calculated empirically from the per cent of chloroform extract b y subtracting 0.5 and multiplying b y j.
$ 0
4!
'1 15
12 9
6
3 O - ' r '
/5
l>IC.
'
30
'
45
'
' 60
75
'
'
90
0
'
15
m
'
30
'
45
'
Minutes t o Penefra +ion - G-zs 6-ACCELERATED AGINQ AT 130' c. PERMEABILITY
'
60
C A R B O N was determined b y digesting I g. of a fresh sample successively with concentrated nitric acid, dilute ammonia containing ammonium chloride, a n d finally dilute hydrochloric acid. It was filtered through t h e same tared filter paper each time and thoroughly washed with hot water. The paper was dried in a n oven a t about rooo C., desiccated, a n d weighed. The difference between this weight and t h e filter paper tare gives t h e weight of carbon plus t h e mineral. By igniting this in a porcelain crucible t h e carbon is burnt off, leaving t h e mineral. The loss in weight is t h e carbon. T O T A L S U L F U R was found by continuously fusing a fresh ]jz-g.sample with a mixture of sodium carbonate and potassium nitrate, lixiviating with water, filtering, precipitating as sulfate, and calculating t o sulfur. "GUM" is found b y difference, as there is no satisfactory method for determining i t directly. It is therefore subject t o t h e accumulation of errors in t h e balance of t h e analysis, which may a t times be considerable. For instance, in t h e calculation of bitumen from chloroform extract, t h e result is only a very rough approximation. Therefore, t h e extra table of analytical d a t a giving t h e compounded materials in round numbers based, as clo:jely as possible, on t h e actual analysis, and on manufacturers' custom in compounding, is helpful in comparing t h e composition of fabrics. The methods of analysis of t h e rubber part of t h e fabric are exact except in three instances. T h e percentage of bitumen is very approximate because it is calculated on t h e per cent of chloroform extract, which represents a n amount ranging from I O t o 30 per cent of t h e bitumen present in t h e compound. Crude gum is determined b y difference and may vary b y several per cent, since t h e percentage is affected b y
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
44 2
TABLEV-CESMICAI.
SAMPLB No. Sp. Or. P-196
1.50
P.197
1.25
P-198
1.30
P-298
1.29
P-199
1.01
P-200
(1.01)
P-299
(1.01)
P-297
1.51
P-205
1.04
P-366
1.03
Insol. in Thick- HCI Pb ness Per Fe+A1+0 Per Inch cent P e r c e n t cent Barytes Sulfate 0.01531.7 0.7 5,.2 Talc Oxide 0.012 13.6 0.9 10.2 Talc Oxide 0.011 12.5 1.2 10.2 Talc Oxide 0.011 17.2 0.6 9:O Talc Oxide 0.018 0.7 0.5 2,8 Talc Oxide 0.016 0.7 0.8 2.9 Talc Oxide 0.012 0.7 0.3 3.2 China clay Sulfate 0.010 36.9 10.2 Talc Oxide 0.019 1.2 Trace 1,2 Talc Oxide 0.8 Trace 2.3 0.018
...
Total of ZOO MgO 6Cols. Per Ca(0H)z Per Precent Percent cent ceding
...
1.5
3.1
1.9
3.5
... ... ...
-Original-
wt.1
P-196 P-198 P-199 P-205 1 Wt.
18.9 60 14.0 55 17.1 60 16.7 41 0 2 . per sq. yd.;
.
-
w1
Per cent
-
ChloroAcetone Free Acetone form BituExtract S Extract Extract men Uncorr. Per Corr. Per Per Per cent cent Percent cent cent
PetroCar- leum Total bon Wax S Per Per Per cent cent cent
Gum Per cent
6.1
0.8
5.3
2.4
9.5
21.7
1.0
3.1
25.6
0.3
4.3
7.4
34.5
6.4
...
0.5
25.4
3.9
2.1
3.4
33.3
35.4
4.6
0.3
4.3
8.3
39.0
4.7
...
0.6
22.4
3.0
0.7
3.3
33.8
33.6
4.7
0.8
3.9
2.4
9.5
5.0
2.7
1.6
47.4
0.5
2.5
0.6
7.6
7.9
5.4
...
2.7
1.0
8.1
7.9
5.4
0.3
5.0
4.9
7.2
0.6
...
47.7
49.1
2.7
. . . . . . . . . . . . 3.3 ... . . . . . . . . . . . . 1 . 6 ... 1.9 5.3 . . . . . . 3.1 ... 1.0 1.7 ............
...
4.0
0.7
7.1
6.8
8.6
1.8
6.8
1.4
4.5
5.5
1.8
2.0
79.1
2.4
1.0
1.4
7.9
7.5
7.3
2.0
5.3
0.9
2.0
6.0
...
3.0
81.1
0.5
...
...
PetroMag- Car- Bitu- leum Sulnesia bon men Wax fur Gum Per Per Per Per Per Per cent cent cent cent cent cent 20 0 10 0 1 . 0 3 . 0 30 0 3:s 5:o 36:o 0 . ~ 5 2510 3.5 5 . 0 36.0 0.5 25.0 4.0 5.0 10.0 2.5 1 . 5 45.0 3.0 2.5 88.0 3.0 2.5 88.0 3.0 4.5 88.0 4 . 0 50.0 5.0 5.0 1.5 2.0 80.0 5.0 2.0 3 . 0 85.0
... ...
I t appears t h a t , up t o I O per cent, bitumen is not harmful, and probably desirable as far as weathering is concerned. Whether t h e poor quality of the Kenyon fabrics, P-197 and P-198, is due t o too much bitumen or insufficient gum, or both, cannot be said with certainty. Magnesia and zinc oxide should be left out, and probably petroleum wax might better be omitted. Litharge and basic lead sulfate should not be present in too great amounts.
86.6 87.9
5.0
86.9
4.8
47.5
TENSILE STRENGTH
Tensile strength of t h e fabrics weathered in Pensacola was tested by the Bureau of Standards a t various times. Tests were made by t h e strip method, using a strip I in. by j in. with a 3 in. separation of the jaws. The d a t a set forth in Table VI1 show P-196 to be as strong as ever after exposure t o weather for 4 mo. Tyie other fabrics have lost from 15 per cent t o 30 per cent of their original tensile strrength. This loss in tensile strength is due t o weakening of the fabric which determines t h e ten:ile strength of the combinatm.?. P-196 probably resisted weathering better becai,se t h e rubber film was still unimpaired after 4 mo., while t h e other samples were more or less crncked and allowed light t o penetrate t o t h e fabric. Deterioration in tensile strength is apparently not sufficiently rapid t o impair the usefulness of the fabric over a period of 6 mo.
TABLEV I I - E ~ ~ ~ E R I O R A T IIN O NTENSILE STRENGTH Fabrics set out io Pensacola, Fehruary 18, 1918, rubber side up -April 21, 1918-May 20. 1918-June 5, 1918--Wt. w F Wt. F wt. w F 19.2 54 61 18.0 61.5 42 17.5 58 51.3 14.2 49 48 13.5 55.3 39.7 13.0 47 36 16.5 51 51 16.4 50.5 45.7 16.2 46 39.3 16.0 50 49 15.4 53.8 47.8 15.4 53.8 47.8 Warp; P Filling.
-
2.5 2.4
It is desirable t h a t fabrics be under-vulcanized when manufactured with enough excess sulfur t o allow a slow after-vulcanization on exposure, thus insuring t h a t the fabric remain soft and flexible for a longer time. The poor quality of P-197 and P-198, Kenyon samples may be due t o insufficient sulfur as well as too large a percentage of bitumen and too small a percentage of rubber. Likewise the poor elastic properties of P-199 and P-200, Goodrich, may be due to insufficient sulfur (see Table VI).
w
F1 52 53 54 57 W
Ash
4.6
filler a n d 2 0 per cent carbon, and has by far t h e best appearance. Whether or not its excellence is due t o t h e large amount of carbon it contains is a question. There are not sufficient d a t a to conclude t h a t a large amount of carbon preserves t h e efficiency of rubber, but i t is not unlikely, inasmuch as it would protect the rubber from the action of sunlight. An analysis for carbon alone on P-190, an e-trlier sample from the Plymouth Company, supports this view, as it contains about 2 0 per cent carbon and is one of t h e three best fabrics investigated.
No.
COMPOSITION
38.1
... ... .. .. .. .. .. .. .. ... ... . . . . . . . . . . .... . . . . . . . . . ..... .. .. .. .. ... ... .... ... ...... ...
FABRIC
No. 5
34.9
COMPOSITION OF MIX
Basic HYSul- Lith- Zinc drated Filler fate arge Oxide Lime SAMPLEPer Per Per Per Pes No. cent cent cent cent cent 1 0 P-196 30.0 5.0 P-197 15.0 io16 i:o 2:o - ~. 15.0 10.0 3 . 0 2 . 0 P-198 18.0 P-298 10.0 3 . 0 1.0 P-199 1.0 3.0 0.5 2.0 1.0 3 . 0 0.5 2.0 P-200 1.0 3 . 0 0.5 P-299 35.0 10.0 1.0 P-297 1.0 1.5 4.0 P-205 1.0 2.0 2.0 P-366
11,
33.2
Trace39.1
t h e total analytical error. It is also difficult t o determine whether lead is present as basic lead sulfate or litharge. But few generalizations can be made from t h e results of chemical analysis of t h e several fabrics. It will be observed t h a t t h e six best fabrics, with t h e exception of P-196, are mostly gum., From this i t appears t h a t fabrics without considerable filler are perhaps best. P-196, however, contains 3 2 per cent inorganic TABLE VI-PROBABLE
Vol.
-July Wt. 18.7
15, 1918-
W 51
F 49.5
.. .. .. .. .. .. .. .. .. .. 46 36.5
14.6
EBFECT O F W E A T H E R CONDITIONS
Fabrics exposed in Washington during the pericd from May to August (average temperature, 73' F.) deteriorated much more rapidly than those exposed during the winter months (average temperature, 58' F.). This was due undoubtedly t o the increased temperature and increased total radiation. D a t a on weather conditions are given in Tables VI11 and IX.
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 CHEMISTRY
May, 1919
WASHINGTON TABLFVIII-DATA c)N WEATHERCONDITIONS,
Total Averaee - - - - - RadiaP.re: Average - M e a n tion cipi- Days on Rela- Temper- Cals. tation which It tive Hu- ature per Sq. Inch Rained midity Deg. F. Cm. 45 16,588 0.136 18 64 52 4,856 0.006 1 56 50 4,183 0.331 7 75 58 6.758 0.137 6 60 69 9,061 0.086 5 66 75 7,514 0.085 5 73 .. 48,960 0:i34 66 55 43 7 3,111 81 75 0.084 4 3 622 68 76 4 0.087 4:085 71 0.061 60 4 69 0.010 3,627 61 2 6 465 69 67 5 0.080 6:935 72 63 6 0.128 6,941 78 74 7 0.130 34,786 69 i3 497 0 : 092 A". . .-
No. DATES Days Feb. 14-Mar. 2 7 . . . 42 Mar. 28-Apr. 6 . . 10 Apr. 7-Apr. 20 ....... 14 Apr. 21-May 4 14 M a y 5-May 21.. 17 M a y 22-June 5 . . 15 TOTAL 112 DAILYAVERAGE M a y 25-May 31. Tune I-Tune 7.. June 8-june 14. 7 June 15-June 21.. 14 June 22-July 5.. 14 July 6-July 19.. 14 July 20-Aug. 2.. TOTAI 70 DAILYAVERAGE..
.. .... ....... .... ....
............ .......
...... i6 ... ..... .....
.....
.............
.....
TABLEIX-DATA
~
.. ..
..
..
WEATHERCONDITIONS, PENSACOLA, FLORIDA Average Averaqe Precipi- Days on Average Mean TemNo. tation which It Relative perature DATES Days Inch Rained Humidity Deg. F. 11 0.050 2 84 61 Feb. 18-Feb. 28 14 0.004 1 90 67 Mar. 1-Mar. 14... 7 0.011 1 70 61 Mar. 15-Mar. 21.. 25 0.231 6 79 62 Mar. 22-Apr. 15.. 20 0.415 6 85 66 Apr. 16-May 5 12 0.095 1 87 72 M a y 6-May 17.. 11 0.001 1 80 75 M a y 18-May 28.. 3 7P 79 M a y 29-June 11.. 14 0.058 67 DAILYAVERAGE,. 114 0.147 82 ON
..... .... .. ...... ... .. .. .
..
SUMMARY
With t h e exception of Kenyon Company fabrics, P-298, P-197, and P-198, t h e different. fabrics deteriorate only very slowly over a period of 100 days; there is a general relation between increase in acetone extract and increase in permeability; t h e
r
fabrics exposed from February t o June (average temperature 58' F.) deteriorate more slowly t h a n those exposed in the warmer weather from June t o August (average temperature 73 O F . ) ; fabrics exposed with rubber side down showed no appreciable deterioration over t h e whole period; fabrics exposed rubber up, b u t shielded from ultraviolet light, deteriorated at about t h e same rate as those exposed t o t h e direct rays of t h e sun; and there is no apparent relation between t h e results of weather aging and an accelerated aging test a t 130' C. Tensile strength of all fabrics is decreased about 1 5 per cent b y t h e exposure. Exposure t o high concentrations of phosgene for I j hrs. rots t h e fabric and rubber. Chemical analysis of t h e fabrics appears t o indicate t h a t over I O per cent bitumen is undesirable and t h a t as high as 2 0 per cent of carbon tends t o preserve t h e fabric, especially when exposed t o sunlight. Fabrics with a high percentage of gum are, in general, more resistant t o t h e effects of weather t h a n those containing a large amount of filler. Results indicate t h a t any of t h e fabrics tested, with t h e exception of t h e Kenyon Company fabrics, are satisfactory from t h e point of view of resistance t o weather. GAS MASK RESEARCHSECTION RESEARCHDIVISION, C. W. S , U. S. A. STATION AMERICANUNIVERSITYEXPERIMENT WASHINOTON, D. C.
I
ORIGINAL PAPERS
THE DETERMINATION OF THE FREEZING-POINT CURVES AND DENSITIES OF DENATURED ALCOHOL-WATER MIXTURES By CLARKEE. DAVIS AND MORTIMERT. HARVEY Received December 27, 1918 INTRODUCTION
The great importance of denatured alcohol as a means of protecting t h e radiator and cooling system of automobiles, air planes, and trucks from freezing has prompted t h e authors t o undertake a n investigation of t h e freezing-point curve of mixtures of completely denatured alcohol and water. This information is necessary in order t o determine how much denatured alcohol should be added in order t o secure protection t o a particular temperature. While t h e curve for mixtures of ethyl alcohol and water has been previously investigated, we have found no record of any work on completely denatured alcohol-water mixtures. The object of this investigation has been t o determine t h e temperatures at which equilibrium exists in systems in which t h e liquid phase is composed ofcompletely denatured alcohol and water and in which t h e solid phase is ice. H I ST ORICAL
Raoultl states t h a t mixtures of alcohol and water when subjected t o low temperatures congeal b u t never completely solidify. T h a t which solidifies con1
443
Compt. rend., 90 (1880). 865.
sists of plates of pure ice and can be freed from alcohol by simple mechanical means. Alcohol Volume in 100 g. Alcohol Water Per cent Grams 0.0 0.0 1.6 1.32 3 2 2.65 4.8 3.97 6.3 5.50 7.8 6.62 9.2 7.95 10.6 9.27 11.8 10.60 13.1 11.90 14.2 13.00 16.4 15.30 18.7 17.80 20.4 19.80
.
Temperature of Congelation Deg. C. -0.0 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0 -3*5 1 -4.0 4 . 5
-5.0 -6.0 -7.0 -8.0
Volume Alcohol Per cent 21.9 23.3 26.4 29.1 31.3 33.8 36.1 t38.3 40.0 41.6 43.7 46.2 47.9
Alcohol in 100 g. Water Grams 21.90 23.60 27.60 31.30 35.10 39.00 42.80 46.60 50.60 54.80 59.20 64.40 70.00
Temperature of Congelation Deg. C. -9.0 -10.0 -12.0 -14.0 -16.0 -18.0 -20.0 -22.0 -24.0 -26.0 -28.0 -30.0 -32.0
These results are graphically represented by t h e curve of Fig. I . Pictetl gives t h e following results of t h e determination of t h e freezing points of mixtures of ethyl alcohol a n d water. Alcohol
Per cent
by Weight 2.5 4.8 6.8 11.3 13.8 16.4 17.5 18.8 20.3
Point of Crystallization Deg. C. -1.0 -2.0 -3.0 -5.0 -6.1 -7.5 -8.7 -9.4 -10.6
Alcohol Per cent b y Weight
Point of Crystallization Deg. C.
46.3
-33.9 -41.0 -51.3
56.1 71.9
The author noted t h e temperature a t the appearance of crystals while t h e mixture was being cooled. 1
Compt. rend., 119 (1894), 678
