Professor Thomas Thomson on the Oxides of Bismuth, 6 



crucible and cautiously dissolved in dilute but pure nitric acid; 

 taking care that while the solution was going on, the crucible was 

 covered with a lid. The liquid portion was now driven out of the 

 crucible by a low heat, and the crucible was kept for some time in a 

 state of incipient incandescence. By this process the 13-5 grains of 

 metallic bismuth were converted into yellow oxide. The amount of 

 yellow oxide in different trials was 14*9, 15* 1, 1505 grains. Hence it 

 follows that yellow oxide of bismuth is composed of 



Bismuth, 13*5 



Oxygen, 1*5 or IJ atoms 



15 

 and that its atomic weight is 15. 1 actually obtained 

 Bismuth, 13'5 

 Oxygen, 1-5016 

 Now 0-0016 grains, being far within the limits of the errors to which 

 such an experiment is liable, ought I conceive to be neglected. 



If 13*5 be the atomic weight of bismuth, then the yellow oxide is a 

 compound of 1 atom bismuth, and l\ atom oxygen. 



The composition of yellow oxide of bismuth thus deduced, agrees 

 with the results which I formerly obtained. I found it composed of 

 Bismuth, 9 

 Oxygen, 1 



10 

 For that reason I considered the atom of bismuth to weigh 9, and the 

 yellow oxide to be 10. But the result of the experiments of Dulong 

 and Petit, of Neuman and of Regnault, to determine the specific heat 

 of bismuth, do not accord with this atomic weight when we test it by 

 the law of Dulong and Petit. We must adopt the number 13-5. 

 And if this be the true number, then the yellow oxide of bismuth is 

 a compound of 1 atom bismuth, and 1 J atom oxygen. 



2. When bismuth in the state of a fine powder is exposed for a long 

 time to the air, or when it is kept melted in a heat under redness in 

 an open vessel, it is converted into a dark brown powder, which con- 

 stitutes an oxide containing less oxygen than the yellow oxide. When 

 we attempt to dissolve it in nitric acid it effervesces and is converted 

 into yellow oxide. I formed a quantity of this oxide by melting bis- 

 muth in a porcelain crucible and stirring it with an iron rod, till the 

 metallic particles nearly disappeared. I then reduced it to a fine 

 powder, and passed it through a hair sieve in order to separate the 

 metallic particles from the oxydized portion. 



20 grains of this oxide were dissolved in nitric acid, the solution 

 was evaporated to dryness, and the residual salt exposed to incipient 

 redness, till all the nitric acid was driven oflF. The weight of the 

 yellow oxide thus obtained was 21*4 grains. 



