212 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



off at a temperature not exceeding a blood heat. Bluish- 

 green crusts are thus obtained which are very friable, and 

 which have a structure similar to malachite. They decom- 

 pose without fusion slowly at ordinary temperatures, more 

 rapidly on heating, evolving sulphurous oxide, and leaving 

 sulphur behind. In a cool place the decomposition is so slow 

 that the substance may readily be weighed for analysis. 

 Moist air decomposes it rapidly, and it hisses when thrown 

 into water. Alcohol and ether also decompose it and set 

 free sulphur. A mean of five closely accordant analyses 

 showed that it contained 57.12 per cent, of sulphur, thus giv- 

 ing it the formula S2O3. The author names it sulphur ses- 

 quioxide, or dithionic oxide. No compounds of it have yet 

 been made. Selenium gives an analogous compound, having 

 the formula SeSOg. It is dirty green in mass, but is yellow 

 when in powder. Poggendorff^s Annalen^ CLYL, December^ 

 1875, 531. 



COEROSION OF PLATINUM STILLS BY SULPHURIC ACID. 



Scheurer-Kestner having communicated to Hofmann, in 

 1862, certain results which he had obtained in the process of 

 concentrating sulphuric acid in platinum stills (which re- 

 sults were published by the latter in his Report on Chemical 

 Industry), and these results having been since that time 

 called in question, the author has examined the facts in the 

 case still more fully, and now publishes a new set of obser- 

 vations. From 1851 to 1861, 4309 tons of sulphuric acid 

 were concentrated to 66 Baume, in an alembic the body of 

 which weighed 40 kilogrammes. The entire loss of this part 

 of the still during this time was 12,295 grammes, being 2.859 

 grammes for each ton of acid worked. Perceiving that the 

 cause of this large loss in platinum was the presence of ni- 

 trous products, ammonium sulphate was added to the acid in 

 amount just sufficient to destroy them. In 1862,1843 tons 

 of acid w^ere concentrated in the still, with a loss of 2490 

 grammes, being only 1.22 grammes of platinum for each ton 

 of acid, a marked decrease. From 1864 to 1875, 17,516 tons 

 (of 1000 kilogrammes each) were concentrated to 66 in a 

 still the body of which weighed 50 kilogrammes. The acid 

 contained sulphurous acid, but no nitrous compounds. The 

 loss of the still was 16,178 grammes, or 0.925 gramme to the 



