TRANSACTIONS OF SECTION B. 677 



Silver nitrate taken, 1-7068 grm.; sulphate found, l'5660grm.; calculated, 

 1-566 grm. 



Potassium nitrate taken, 0-9490 grm. ; sulphate found, 0-816 grm. ; calculated, 

 0-8170 grm. 



Chlorates. — The only salts of this class examined were those of barium and 

 potassium. The first result of impact of the SOo was the liberation of chlorine 

 peroxide, which escaped along with the excess of S0„ as long as the temperature 

 did not rise above about 60° ; at a little higher temperature there was a slight 

 flash in the tube and formation of white fumes of SO.,. The escaping gases then 

 contained chlorine, SO3 and S0„. The yellow but clear mixture of sulphur di-oxide 

 and chlorine peroxide became cloudy from formation of SO3 on introduction of a 

 little moisture. 



Moist S0„ appeared to act more rapidly than dry, and in most cases without 

 visible liberation of chlorine peroxide. 



Barium chlorate taken, 0-480 grm. ; found as sulphate, 0-364 grm. ; calculated, 

 0-367 grm. 



Potassium chlorate taken, 1-0982 grm. ; found as sulphate, 0-7798 grm. ; cal- 

 culated, 0-7797 grm. 



Phosphates are apparently not acted upon at all by SO2. 



With chromates, dichromates, and permanganates considerable differences ot 

 behaviour were noticed, depending evidently on the nature of the metal. "With 

 silver chromate the figures point to the formation of silver sulphate and chromic 

 oxide. 



Silver chromate taken, 0-9348 ; after heating to near redness weight found 

 ■was 1-0934 ; for a mixtm-e of sulphate with chromic oxide it should be 1*092. 



With alkaline chromates, or dichromate, or barium chromate there is an 

 evident tendency to form chromium sulphate as well as other sulphate. In no 

 case, however, has the formation of chromium sulphate proceeded its full extent 

 even when the heating has been continued for many hours in a steady current of 

 S0„. 



Permanganates behave in a similar manner. 



With both classes of salts the action is at first rapid during the formation of 

 the more positive metallic sulphate, and ceases at a higher temperature owing to 

 the decomposition of the chromium and manganese sulphates by heat. 



Grm. 



Potassium bichromate taken .... 1-6214 



After heating in SOo 2-0256 



After reheating for two hours in SOj . . . 2-0468 

 Calculated as a mixture of CroOg and K^SO^ it 



would be 1-7945 



As a mixture of K2SO4 and Cr^CSOJa . . . 3-1214 



Potassium chromate taken -907 



After heating for half an hour in SOo . . . 1-1675 



After reheating for two hours in SO3 . . . 1-2606 



Calculated as a mixture of K^SO^ and CroOg. . 1-1688 



The ease with which potassium nitrate was converted into sulphate by the 

 action of dry SO^ suggested a method for the determination of potassium in gun- 

 powder and similar substances. It was, however, found verj' unsuitable. 



A number of experiments carried out by Lieutenant L. E. Traherne, R.N., 

 show that when gunpowder is acted upon by SOo at about 150°, either dry or 

 moist, the temperature rises quickly, and in most cases causes explosion. With 

 fine-gTained powders, and especially when unglazed, the action is more rapid 

 and the explosion violent, as it appears to take place over a considerable area at 

 once. 



Chlorates, as might be expected, when simultaneously in contact with SO., 

 and any kind of organic matter set up a violent action. A good form of lecture 



