T H E JOURiVAL OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
Nov., 1919
broad bense or from the standpoint of increased production alone, results from developing more than 2 0 per cent sodium cyanide. In the recovery department the difficulties were largely mechanical and quite unimportant. The purity of the sodium cyanide produced averages g z per cent but it is practically free from alkali, iron, and insoluble matter, the main impurity being cyanates. After the first lot produced, the material was nearly pure white, needing no purification before marketing. COST PER POUND SODIUM CYANIDE Raw Materials Cents Mechanical Preparation.. . . . . . . . . . 2 . 3 2 Retort Department.. . . . . . . . . . . . . . 2 . 3 9 Recovery Department.. . . . . . . . . . . 0 . 7 5 Laboratory. ..................... TOTALS.. ................... 5 : 4 6
...........................
All Other Charges Cents 3.41 8.85 2.83 0.23 , 15.32 5.46
__
GRANDTOTAL. 20.78 OF COSTIN TERMS OF THE WORKPERFORMED ANALYSIS Cost per Pound Per cent of ITEM of N a C N Total Cost 7.4982 37.30 Raw Materials.. ............. 1.5986 7.95 P o w e r . . .................... 0.3038 1.51 Steam (not used as power). , 4.5410 22.59 Direct Labor. 0.4025 2 ,oo Indirect Labor.. 1.9300 9.60 Retort Tubes.. 0.822 4.10 Repairs.. 1.1800 5.87 Depreciation.. Contingencies (10 per cent). 1 ,8260 9.08
. . ............... ............. .............. ................... ............... ..
TOTALS . . . . . . . . . . . . . . . . . 20.1021
I
100.00
1013
The cost of making cyanide, applied exclusively to this plant as operated with its military personnel and post organization, was roughly z o cents per lb., calculated in the usual standard manner of cost accounting to include all charges except royalties and profits. This figure, however, would have no particular significance as t o the cost of making cyanide at this plant if costs were reduced to a reasonable basis by virtue of constant operation at capacity. The nitrogen produced by the Claude process at about 2 5 cents per thousand cubic feet could be positively reduced to about I O cents per thousand cubic feet if the capacity of the plant were required. The Freceding brief tables show the cost in cents per pound of IOO per cent sodium cyanide by departments. These two results are not derived from the same data but are independent observations and while disagreeing sliqhtly, are still a notable check on 20 t o z I cents as the cost per pound. A t the conclusion of the project as far as described above the Bureau of Mines turned the property over to the Ordnance Department as originally planned. The personnel were released and steps taken t o salvage the plant. The Bureau of Mines deserves great credit for efficient clean-cut handling of the project. NITRATEDIVISION ORDNANCE DEPARTMENT WASHINGTON, D C.
CONTRIBUTIONS FROM THE CHEMICAL WARFARE SERVICE, U. S. A. A NEW ABSORBENT FOR AMMONIA RESPIRATORS' By G. ST. J. PERROTT, M A XYABLICK AND A. C. FIELDNER Received January 13, 1919
Protection from ammonia gas is needed by workmen in industries where refrigerating plants are used. Leaks often occur which develop concentrations of ammonia as high as 2 per cent. Protection against concentrations as high as j per cent is probably desirable, although this concentration can be endured only for a few minutes, due t o t h e irritating effect of t h e gas on t h e skin. Loss of much time is avoided if workmen are provided with respirators which will enable them t o make repairs in safety at any bearable concentration and at any degree of exertion. Previously, protection from ammonia has been obtained by filtering t h e inhaled air through pumice stone impregnated with sulfuric acid. This absorbent has the disadvantages t h a t a t high concentrations a n d breathing rates ( I ) a great deal of heat is evolved, making the effluent air too hot t o be breathed unless a cooling device is installed, said cooling device taking up practically as much volume as t h e absorbing material, ( 2 ) caustic fumes are produced which must be filtered out with a cotton or felt pad which increases the resistance t o breathing, (3) t h e resistance, initially high, increases during absorption and becomes unbearable before the absorbent is exhausted, and (4) a specially designed canister t o resist corrosion by the acid must be employed. USE
OF
SALTS
FORMING
METAL-AMMONIA
COMPOUNDS
We have found t h a t certain salts which unite with ammonia t o form metal-ammonia compounds provide 1 Published b y permission of the Director of the Chemical Warfare Service.
ideal absorbents for use in a n ammonia respirator. These salts have great activity and capacity, the heat effect during absorption is negligible, no fumes are produced, the resistance increases very little during absorption, and no specially designed container is necessary. Among t h e best known of the metal-ammonia compounds a r e those containing trivalent cobalt, chromium, iridium, and rhodium, and divalent copper and zinc. Salts of iron, magnesium, strontium, barium, mercury, cadmium, calcium, and some other metals form similar compounds. Where anhydrous ammonia acts on the anhydrous salt, a compound of the general formula MXn(NH3)mis formed. When ammonia gas is passed over a salt hydrate a compound of t h e general formula M X , ( N H S ) ( ~ - ~ ) . X H ~ Omay be formed, although in many cases it is probable that a mixture of basic salt, ammonium salt, and metal-ammonia salt is formed. Some of the metal-ammonia compounds have a considerable decomposition pressure of ammonia at room temperature and are not formed a t all a t the coricentrations of ammonia in which we are interested; several others are stable a t room temperature. METHOD O F IMPREGNATING PUMICE STONE WITH THE SALT
I n determining which of a number of salts was most efficient for our purpose, t h e following procedure was carried out: Pumice stone, 8 t o 14 mesh, was impregnated with about 7 0 per cent of its weight of salt. I n carrying out the impregnation, pumice is mixed with salt in t h e ratio 60 per cent pumice by weight t o 40 per cent salt and t h e whole covered with water. The solution is then boiled down with constant stirring until t h e salt has crystallized on the pumice and is almost dry. The
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
1014
material is then spread out and allowed t o dry in the air, after which the fines are screened out on a 14 mesh sieve. This procedure gives us the salt in very fine crystals which have been found t o be more active t h a n larger crystals. The pumice base prevents increase of resistance during service due to the salt dissolving in the water evolved. COMPARISON O F EFFICIENCY
O F VARIOUS ABSORBENTS
The various absorbents were tested for efficiency in small scale tube tests. A j per cent ammonia-air mixture, dried over fused caustic, was passed through 5 in. of the material contained in a tube 7 in. in diameter, a t a rate of 3 liters per min. Presence of ammonia in the effluent air was detected by smell. I n this way the several salts were very quickly rated in order of efficiency. I n order t o get a rough idea of the capacity of the absorbent, the ammonia mixture was run through the absorbent for 30 min. t o I hr. after the first trace of ammmonia was detected in the effluent air, and the change in weight of the absorbent tube and the tube containing fused caustic noted. Obviously the algebraic sum of the gain in weight of the two tubes is equal t o the amount of ammonia absorbed. I n many cases it will be noticed t h a t the salts lost slightly in weight, as is t o be expected where ammonia is displacing water. With a few salts a slight gain in weight is noticed, due probably t o the fact t h a t all the water evolved had not been carried over into the caustic tube. The silica. gel absorbs the ammonia with practically no evolution-of water.
Vol.
11,
So.
11
molecules of ammonia per molecule of cobalt chloride. Copper sulfate comes second, lasting about I O min., and absorbing about 2 0 per cent of its weight of ammonia a t equilibrium or 3 molecules of ammonia per molecule of salt. Silica gel absorbs nearly 2 0 per cent of its weight of ammonia a t equilibrium, but has a considerable vapor pressure of ammonia before equilibrium is reached and hence is not as efficient for our purposes as the cobalt or copper salt. I t has a use in the ammonia canister, however, which will be referred t o later. Cobalt sulfate is not as good an absorbent as copper sulfate. Salts of magnesium, nickel, zinc, aluminum, fgrrous iron, and boric acid also show considerable absorptive power. The copper sulfate absorbent, khich for reasons appearing later is believed t o be the most satisfactory for our purpose, has been named kupramite. MAN
TESTS
OF
CANISTERS
PACKED
WITH
VARIOUS
ABSORBENTS
After the several salts had been rated by the tube test, some of the best of them were packed in canisters and subjected t o actual man tests. Fig. I shows the
TABLE I-TUBE TESTSCOMPARINO EFFICIENCY OF VARIOUS MAT~RIAL ASS ABSORBENTS FOR AMMONIA
ABSORBENT
............
CoC1~.6Hn0 CuSOa.5HzO.
Mg(NOa)z.6HnO.. . . . . . .
.......... Ah(SO&.l8HzO.. ...... CoS04.7HzO..
ZnCln.
.................
FeSOa.7HnO . . . . . . . . . . . NiS04.5HzO.. .. Citric a c i d . . Boric acid'..
...........
..........
40.51 39.37 39.12 44.60 41.40 41.44 41.10 41.43 35.78 36.71 44.63 43.79 34.79 40.50 42.40 39.76 32.87 45.57 29.86
+0.04 -0.57 -0.89 4-2.35 -0.07 -0.13 -0.23 -0.89 -1.20 -0.97 -0.16 -0.12 -0.25 -0.10 -0.25 -0.22 -0.08 -0.45 4-0.72 I 2 9 . 5 2 4-0.78 37.91 Jr0.21 38.71 4-0.27
CO(NO3)z 6HzO ....... j, (so4) ............. Ba(N0s)z. ............. CaCln.Z1/zHaO. ........ Sr(NOs)z.4HzO......... 6
2
4.01 3.80 3.47 0.07 1.45 1.47 2.20 2.74 2.57 2.21 2.33 2.32 1.37 0.37 0.64 0.70 0.45 2.75 0.80 0.16 0.45 0.67
4.05 3.23 2.58 3.42 1.38 1.34 1.97 1.85 1.37 1.24 2.17 2.20 1.12 0.26 0.39 0.48 0.37 2.30 1.52 0.94 0.66 0.94
10.0 8.2 6.6 7.7 3.3 3.3 1.7 2.4 3.7 3.4 4.8 5.0 3.2 0.6 0.9 1.2 1.1 5.0 5.1 3.2 1.7 2.4
25.0 20.5 16.5 19.1 8.3 8.3 4.4 6.1 9.2 8.5 12.0 12.5 8.0 1.6 2.3 3.J 2.8 6.7 12.7 8.0 4.4 6.1
12 f5 1 0 . 5 75 9.0 .. 6 . 5 60
5.0 4.8 4.0 4.0 4.0 4.0 3.0 2.8 2.5 2.0 1.5 2.0 1.5 8.0 0.8 1.0
60
..
60
..
60
..
30 30 45 45
,.
.. 60 60 30
..
1 . 0 30 0.5 _ .
3.
Crz SO4)a.KaS0~.24HzO.. C O I N 0s)z.4HzO.. MnS04.2HzO.. Fez(SOa)s.9HzO. 1 Mixture of 35 parts kieselguhr and 100 parts boric acid (channelling).
...... ........
........
Cobalt chloride appears t o be the most efficient absorbent investigated. I t let through no trace of ammonia for I 2 min. and absorbed 2 5 per cent of its weight of ammonia, an amount corresponding t o about 3.5
FIG. ~-KUPRAMITE AMMONIA CANISTER
standard army canister used in this series of tests. I t is an elliptical container of sheet metal with a capacity of about 45 cud in. of material. This canister was employed in connection with t h e Tissot type mask shown in Fig. 2 . In carrying out the man tests, a gas chamber of about 19,0001. capacity was employed. Canisters were tested a t concentrations varying from 2 t o 5 per cent. It was found t h a t concentrations of ammonia of 2 per cent could not be endured for longer periods than 1 5 min. due to the irritating effect of the gas upon the skin. The canisters were accordingly not run to break down with men inside the gas chamber. Tests t o determine the total life of the canister were run with the canister inside the chamber and connected t o the outside by a rubber tube. The observes was thus enabled
'
XOV.
T H E J O L:R N A L 0 F I N D U S T R I A L A JVD E N G I N E E R I N G C H E M I S T R Y
1919
to wear the mask outside the chamber and t o continue breathing until the absorbent was exhausted without the discomfort of being in the gas. I n the column under breathing rate (Table 11) i t will be noticed t h a t this ran a4 high as 6 0 1. per min. These different breathing rates were brought about by having the men ride a bicycle ergometer with different currents flowing through the electromagnetic brake. The average man breathes about 81. per min. a t rest, 32 1. per min. indicates moderately severe exercise and causes exhaustion in half an hour, a t 60 1. per rnin. exhaustion occurs in about 5 min. The importance of testing the absorbents a t high breathing rates is evident. An absorbent with a large capacity might offer no protection a t all a t high breathing rates due t o the fact t h a t it did not possess sufficient activity. TABLE11-MAN
TESTSOF CANISTERS PACKED WITH DIFFERENT ABSOR-
IO1j
A defect of the metallic salt absorbents, which was a t first noticed and has now been eliminated, was the tendency of the water given off during absorption t o condense on the eyepieces of the mask and diminish the clearness of vision. To remedy this defect a I-in. layer of silica gel or active charcoal is placed on top of the ammonia absorbent. This has been found t o keep the humidity of the effluent air sufficiently below saturation t o prevent condensation on the eyepieces. P O S S I B I L I T Y O F D E T E R I O R A T I O N O F A B S O R B E N T WITH AGE
There is no reason t o suppose t h a t the absorbent will not retain its efficiency indefinitely. We have not yet had time t o conduct any extensive series of aging tests; such tests are, however, under way. Canisters tested three weeks after packing have shown no apparent decrease in life.
BENTS
FILLING CoCh.6HzO.
.....
,. .. ,. ....
. 50 .. 50
CuSO4.5HaO..
?O ..
..
BeSOr.7H9O.. ~ . . _ .
...
50 70 70 70 50
..
5 5 5 5 5 3
5
50 45 45 47 34 45 47 54 52 45 42 42 48 48 64 50 50
60 60 58 53 38 58 60 58 58 53 60 43 61 60 70 65 58
192 122 13 16 4 240 240 120 110 184 166 48 26 31 5 160 120
8 8 32 32 60 8 8 8 8 8
8 20 32 32 60 8
8 Silicic acid.. ................. 5 0 per cent boric acid, 50 per 50 cent kieselguhr. ........... . . 60 120 8 The weight of the 45 cu. in. of impregnated pumice is between 500 and 550 g.
The three salts, copper sulfate, cobalt chloride, and ferrous sulfate were put on 8 t o 14 mesh pumice in the manner previously described. Silicic acid was made by the decomposition of sodium silicate with acid and subsequent partial dehydration of the resulting product a t a temperature of about 125’ C., after t h e method of Patrick.’ The figures under pressure drop show the resistances of the canister a t the beginning and end of the test expressed in millimeters of water when a n air flow of 85 1. per min. is passing through the canister. Results of the man test show t h a t either cobalt chloride or copper sulfate give a n absorbent with a capacity more t h a n adequate for any conditions which i t is possible t o conceive the canister might meet in service. For a man a t rest t h e canister filled with either of these absorbents has a life of about 5 hrs. against 2 per cent ammonia, a concentration which is unbearable, due t o skin irritation, for periods over 1 5 min. The canister has even longer life on a n intermittent test. A canister filled with the copper sulfate absorbent was run on t h e regular man test against 2 per cent ammonia for I hr. a day on successive days until breakdown. T h e total service time of the canister under these conditions was 8 hrs. and 56 min. A canister filled with silicic acid and tested in a similar manner, lasted 4 hrs. and 8 min. 1
W. S. Patent 1,297,724.
FIG. &-AMMONIA
RESPIRATOR, SHOWING CANISTER
C A R R I E D ON
BACK
It has been found t h a t the efficiency of the absorbent one day after preparation is somewhat greater than the efficiency a week after preparation. Further exposure does not cause any‘ apparent decrease in life. If the absorbent is allowed t o stand over I : I sulfuric acid for a week, t h e life is cut in half, while if t h e absorbent is allowed t o stand over water for the same time t h e life is increased about 2 5 per cent. Evidently it is necessary t h a t the copper sulfate be present in the form of the pentahydrate and undoubtedly a slight excess of water would aid in prolonging the life. It is possible t h a t the addition of a small per cent of a deliquescent material t o the original mix would prove of benefit. Tge whole question of increasing the life of the absorbent is being investigated in some detail. Very promising results have been obtained by making granules of a mixture of copper, sulfate, kieselguhr, and a cement. I n this way an absorbent can be made which contains a very large proportion of the active material in a finely
1016
T H E J O U R X A L OF T 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
divided state and a relatively small proportion of inert material. RE C 0 $1 M E i i D E D C 0 N ST R U C T I 0 N 0 F A M M 0 pi1A R E SPI RAT 0 R P R E P A R A T I O N O F ABSORBENT-Pumice Stone, 8 t o I 4 mesh, and technical copper sulfate are placed in an evaporating pan in the ratio of one part by weight CuSO4.5H2O t o 1.5 parts pumice, and the whole is covered with sufficient water t o dissolve t h e salt a t boiling temperature. The mixture is then boiled down with constant stirring until crystallization takes place on t h e pumice and t h e crystals are nearly dry. The pumice thus treated is then removed from the dish, spread out and allowed t o dry in the air. The fines are then screened out on a 14 mesh sieve. Care must be taken in the evaporating process t h a t t h e absorbent is still slightly moist when taken from the pan.
voi.
11, NO.
II
eyepieces of the mask and thus impairing the vision of the wearer. To remedy this defect a I-in. layer of kupramite a t the top of t h e canister is replaced by activated charcoal or silica gel, preferably silica gel. This decreases the humidity of the effluent air sufficiently t o prevent dimming of the eyepieces. If charcoal is used, a 2-8. cotton pad (Eastern Star Furrier Co., Pawtucket, R. I.) is substituted for the toweling in order t o remove charcoal dust. The canister complete weighs about 1 . 7 lbs. T Y P E O F FACEPIECE-The present standard type of army gas mask with mouthpiece and noseclip may be used, in which case no silica gel or charcoal need be placed in the canister. On the other hand the Tissot type facepiece shown in Figs. z and 3 is much more comfortable t o wear because of the elimination of mouthpiece and noseclip; furthermore, t h e wearer has a larger range of vision and can work t o better advantage. The photqgraph shows the canister carried on the back; the position on t h e chest as used by the Army is probably better for certain kinds of work. The complete respirator weighs about 3. j lbs. A simple mouthpiece and noseclip and separate goggles should never be used, as no goggles have yet been p u t on t h e market which will protect t h e eyes from ammonia in high concentration. We wish t o express our appreciation of the cooperation of Louis Jordy and 0. P. Gephart in conducting the man tests, and of J. H. Yoe in conducting machine tests. Acknowledgment is due t o the Bureau of Mines and especially t o the Director, Van' H. Manning, for initiating t h e work on t h e industrial gas mask and for t h e valuable assistance of the Gas Investigations Labofatory of the Pittsburgh Station of t h e Bureau of Mines. SUMMARY
Pumice stone impregnated with copper sulfate has been shown t o have a large capacity for absorbing ammonia. A canister containing 4 j cu. in. of this material will protect a man breathing a t rest for a t least 5 hrs. against z per cent ammonia and for z1/2 hrs. against 5 per cent ammonia, Tests at high breathing rates show t h a t the canister affords ample protection even a t severe exertion. Several other salts, and boric a n d silicic acids are also good absorbents. The advantages of the present absorbents are large capacity and activity, negligible heat of absorption, and cheapness. GASMASKRESEARCH SECTION RESEARCH DIVISION, C . W. S., U. S. A. AMERICAN UNIVERSITY EXPERIMENT STATION WASHINGTON,
FIG. 3-AMMONIA
RESPIRATOR, S H O W I N G RELATIVE SIZE
OR C A N I S T E R
CANISTER-Fig. I shows the standard army canister packed with kupramite. A layer of toweling is placed on top of the absorbent t o filter out any fine particles which might be drawn up from t h e %bsorbent, and the whole is held in place by t h e usual heavy wire screen and spring. This method of packing is t o be used with the present mouthpiece type of army mask described below. If the new Tissot type mask is used, a modification of the packing is desirable in order t o eliminate t h e trouble due t o moisture given off by the absorbent during service condensing on the P A C K I K G OF THE
n.c.
EFFECT OF MOISTURE CONTENT ON THE PERMEABILITY OF FABRICS TO MUSTARD G A S B y GEORGBH. CLOWES,G. S T . J. PERROTT, BENEDICT GORDONA N D
E. L.
GREENSFELbER
Received August 25, 1919
The purpose of this paper is t o determine t o what extent the permeability of various fabrics t o mustard gas may be modified by the addition of varying proportions of moisture. Since mustard gas is only slightly soluble in water, and in aqueous solution undergoes hydrolysis with 1 Published by permission of the Director of the Chemical Warfare Service, U . S. A.
D
