« Professor Thomas Thomson an the Oxides of Bismuth. 



without any sensible action. It has the property of dissolving yellow 

 oxide of bismuth. By repeated digestions in successive portions of 

 distilled vinegar, I succeeded at last in separating the whole yellow 

 oxide, and thus obtaining the peroxide in a state of purity. 



It was in very small scales having a silvery lustre, and had a brown 

 or rather a buflf colour, not so dark as that of the original mixture of 

 yellow and brown oxides. It was tasteless, heavy, insoluble in water, 

 and acted on by acids in the way just stated. Neither the fixed 

 alkalies nor ammonia have any sensible action on it. 



To prepare it for analysis, I washed it with water till that liquid 

 came off perfectly pure. I then dried it in the open air, and finally 

 kept it in a temperature of 300° till it ceased to lose any weight. I 

 then put it into a platinum crucible, and gradually heated it by a 

 spirit lamp till it was converted into yellow oxide. Two successive 

 experiments yielded exactly the same result. 19-8 grains of it lost, 

 when thus treated, 2*1 grains of weight, and were converted into yellow 

 oxide. So that peroxide of bismuth according to this result is 

 composed of 



Yellow oxide, 17*9 or 15 

 Oxygen, 1-9 or 1*59 



This is very nearly one atom of yellow oxide and an atom and a 

 half of oxygen. I have no doubt that the exact quantity of oxygen is 

 1*5 or an atom and a half. Thus we have the atomic weights and 

 composition of the suboxide, the yellow and brown oxides of bismuth 

 as follows : — 



Bismuth. Oxygen. 



Suboxide, 2 atoms, -j- 1 atom. 



Yellow Oxide, 1 — + U — 

 Peroxide, 1 — +3 — 



The atom of bismuth must weigh 13*5. 



I found the brown oxide of bismuth as originally prepared, by boil- 

 ing yellow oxide in chlorite of soda, a compound of 



12*25 yellow oxide. 

 2*75 brown oxide. 

 Or nearly 5 atoms yellow oxide, and 1 atom brown oxide. 

 It is obvious, from the results just stated, that Stromeyer had not 

 succeeded in freeing his brown oxide from all admixture of yellow 

 oxide. 



The constitution of the oxides of bismuth would be simplified were 

 we to double its atomic weight, and make it 27. Then the suboxide 

 would be a compound of 1 atom bismuth and 1 atom oxygen, the yellow 

 oxide of 1 atom bismuth and 3 atoms oxygen, and the brown oxide, a 

 compound of 1 atom bismuth and 6 atoms oxygen. But the experi- 

 ments made to determine the specific heat of bismuth, will not admit 

 of any such increase. This specific heat is — 



