94 On the Composition of Blende. [Au«. 



Zinc 5909 



Sulphur 28'Hfi 



Iron 12-05 



100-00 



From the result of this analysis, which was fully confirmed by 

 several others, I conside;* myself as warranted to conclude, that 

 both the zinc and the iron exist in blende in the metallic state. I 

 think it equally evident, thai the iron is not combined with sul- 

 phur, but only the zinc; for if we suppose that one atom of zinc 

 combined with one atom of sulphur constitutes sulphuret of zinc, 

 and if we assume the weight of an atom of zinc at 4-139, and an 

 atom of sulphur at 2, according to my previous determination of 

 these weights, in that case 59-09 of zinc ought to combine with 

 28 - 55 of sulphur. Now this very nearly agrees with the numbers 

 in the preceding table. Sufficiently so at least to demonstrate that 

 none of the sulphur can be in combination with the iron. 



If we consider the preceding experiments as correct, and they 

 were made with so much care that I am myself disposed to rely on 

 them, sulphuret of zinc is composed of 



Zinc G7'19 100- 214-40 



Sulphur . . 32 81 4S-S4 100 00 



100-00 148-84 31140 



Were we to suppose this determination rigidly accurate, it would 

 occasion a small alteration in the weight of an atom of zinc, and 

 likewise in the constitution of oxide of zinc. 1 am disposed to put 

 more confidence in it than in my preceding experiments to deter- 

 mine the composition of oxide of zinc by dissolving that metal in 

 nitric acid, and weighing the oxide obtained, or by dissolving it in 

 sulphuric acid, and calculating from the proportion of zinc dis- 

 solved how much oxygen it must have combined with ; for the zinc 

 of commerce, upon which my experiments were made, is never quite 

 free from lead. And though I endeavoured to determine the quan- 

 tity of that metal present, and to allow for it, such a determination 

 was liable to uncertainties, from which the analysis of blende was 

 free. 



I shall therefore henceforth consider an atom of zinc as weighing 

 4-095, and oxide of zinc as composed of 100 metal + 24*42 

 oxygen. What renders me more disposed to adopt these new num- 

 bers is, that they approach nearer to the determination of Berzelius 

 than any of my preceding numbers. And the accuracy of his ex- 

 periments I have had occasion in many repetitions ot them, to ad- 

 mire as most extraordinary. He found oxide of zinc composed of 

 100 metal + 24-4 oxygen. My first determination was 100 

 metal + 23 - 5 oxygen; my second 100 metal -f 24-16 oxygen; 



