162 THE NEW WORLD OF SCIENCE 



needs of the navy, but this absorbent has already found very 

 practical use in connection with refrigeration plants. The 

 previous protection had been obtained by the use of pumice 

 stone impregnated with sulfuric acid. Such protection had 

 serious disadvantages. These were largely overcome by the 

 substitution of certain salts which form metal-ammonia com- 

 pounds. Of these, cobalt chloride or copper sulfate are by 

 far the best absorbents for ammonia. The pumice is added to 

 a solution of copper sulfate and the mixture heated until the 

 salt crystallizes on the pumice and the crystals are nearly dry. 

 Moisture that may be given off by the absorbent is removed by 

 placing a one inch layer of charcoal or preferably silica gel 

 at the top of the canister. With 45 cu. in. of this material, 

 protection is afforded for 5 hours against 2 per cent, ammonia 

 (man breathing at rest) or for 2.5 hours against 5 per cent, 

 ammonia. For periods over 15 minutes 2 per cent, ammonia is 

 unbearable, due to skin irritation. The copper sulfate canister 

 has been named the Kupramite ammonia canister and is being 

 manufactured by at least two concerns at the present time. 



Absorbents, however, were only one, though a very important 

 phase of the work. The great disadvantage of the British 

 Standard Box respirator was the fact that the design of the 

 face piece, consisting as it did of a nose clip and mouth piece 

 as a " secondary line of defense," decreased seriously the 

 efficiency of the men. The French early recognized this and 

 developed their Tissot type of mask for the artillery men. 

 While the English apparently never saw fit to develop this 

 further, the Chemical Warfare Service saw its great advantage 

 and modified it in various ways, producing the Kops-Tissot, the 

 Akron-Tissot, the Miller-Tissot and the Lakeside-Goodrich 

 masks. All of these were designed upon the same basic prin- 

 ciple. The air, passing through the canister, was drawn up into 

 the mask so that it passed over the eye pieces before being 

 breathed. In doing away with the mouth piece and nose clip, 

 it was essential that the rubber face piece should be so rein- 

 forced that it would not be easily torn. This involved intensive 



