Professor Thomab Thomson on the Oxitles of BisrmUh, 7 



But he hit upon another and much easier method of preparing per- 

 oxide of bismuth. When yellow oxide of bismuth is mixed with a 

 solution of chlorite of soda, and boiled in a flask, it soon assumes a 

 dark brown colour, like that of peroxide of lead. Chlorite of soda is 

 obtained by dissolving bleaching powder in water, and precipitating 

 the lime from the solution by carbonate of soda. The boiling must 

 be continued for some time. And then the brown powder is collected 

 on the filter, washed and dried. In this state it is almost black, but 

 is still a mixture of yellow oxide and peroxide. Stromeyer purified it 

 by washing it in cold nitric acid, diluted with nine times its weight of 

 water. According to the analysis of Stromeyer, 12*12 of it when 

 heated to about 660° become yellow oxide, and lose 0*59 of oxygen. 

 Hence 15 grains of yellow oxide in order to become peroxide must 

 combine with 0*767 of oxygen. Hence he concludes, that the oidde 

 of bismuth is a compound of 



1 atom yellow oxide bismuth, 15 

 I atom oxygen, 0*75 



15-75 



So that its atomic weight is 15*75, and it consists of 



1 atom bismuth, 13*5 

 2^ atoms oxygen, 2*25 



15*75 



These atomic proportions appeared so unusual that I thought them 

 not likely to be correct. It would indicate a compound of 4 atoms 

 bismuth, and 9 atoms oxygen, as the constitution of peroxide of bis- 

 muth, I therefore prepared a quantity of peroxide of bismuth, by boil- 

 ing anhydrous yellow oxide in fine powder with liquid chlorite of 

 soda in a flask. I allowed the boiling to continue for 24 hours. 



The product was a dark brown powder, very heavy ; but in colour 

 similar to peroxide of lead. It was easy by the application of dilute 

 nitric acid, to detect in it the presence of yellow oxide of bismuth. 

 But I found some difficulty in separating this yellow oxide ; muriatic 

 acid was out of the question, as chlorine was evolved and the whole 

 oxide speedily reduced to common chloride of bismuth. I tried nitric 

 acid, which Stromeyer employed, but it effervesced with the peroxide, 

 evolving oxygen, and before I could succeed in removing the yellow 

 oxide almost the whole of the peroxide disappeared. Sulphuric and 

 phosphoric acids did not answer better. They caused an eflfervescence 

 with the evolution of oxygen, and the peroxide was gradually reduced 

 to yellow oxide. I did not try sulphurous acid, thinking it not at all 

 likely to answer. But Stromeyer says that it slowly changes the per- 

 oxide of bismuth into subsulphate. At last, after a great many fruit- 

 less trials, I found that dilute acetic acid might be digested upon it 



