THE CHEMICAL WARFARE SERVICE 159 



keiselguhr, which seems to increase the degree of hardness. 

 The sodium hydroxide served to give the granules considerable 

 more activity and at the same time maintains roughly the proper 

 moisture content. 



The above mixture is dried to about 8 per cent, moisture 

 and then sprayed with a solution of sodium permanganate. 

 This acts as the oxidizing agent in the finished granule. Of the 

 five commercially available permanganates, sodium was the 

 only one meeting all the requirements. It makes up about 3 per 

 cent, of the granule, the moisture content of which ranges 

 about 13 per cent. 



The use of large amounts of sodium permanganate neces- 

 sitated the working out of a method for its manufacture. It 

 was found that a 30 per cent, solution could be prepared by 

 the fusion of sodium hydroxide and manganese dioxide, leach- 

 ing, and chlorination of the sodium manganate in the presence 

 of a catalyst. Another method developed consisted in the 

 electrolysis of sodium carbonate solution in a diaphragm cell 

 with ferro manganese anodes. The current density used is 

 about 1 20 amperes per square foot and the temperature may 

 be about 20 C. The anodes gradually accumulate a skin of 

 oxides of iron, manganese and silicon, which is easily removed 

 every 24 hours by sand blasting. It is not feasible to run 

 beyond an 8-12 per cent, solution of sodium permanganate, 

 which is then concentrated to about 30 per cent. Under war 

 conditions, the cost was estimated at about 60 cents per pound. 



CARBON MONOXIDE ABSORBENT 



Another very important phase of work on absorbents was 

 concerned with carbon monoxide. While not sufficiently toxic 

 to be used as a poison gas, it is a source of serious danger both 

 in marine and land warfare. It is encountered as the result 

 of defective ventilation in boiler rooms of ships, in pill boxes 

 and in tanks and in mining and sapping work. In times of 

 peace, the gas is also a serious hazard and it was realized that 

 the successful solution of the problem of protection against 



