336 DR T. THOMSON on the Composition of Blende. 



water. But at so low a temperature it is not probable that the 

 powder would be deprived completely of water. Yet AEFWED- 

 SON estimated the weight of the sulphur, by subtracting the 

 weight of the zinc obtained from the original weight of the pow- 

 der. The remainder he considered as sulphur. Now, certainly, 

 this remainder was not all sulphur, a portion of it must have 

 been water ; therefore the quantity of sulphur which ARFWED- 

 SON gives is greater than what was actually present in the 

 blende. 



2. From a very great number of experiments which I have 

 made on the various modes of obtaining zinc from its acid solu- 

 tions, I am satisfied that, by the method employed by ARFWED- 

 SON, the whole of that metal cannot be obtained. It is plain, 

 then, that the blende analyzed by him contained more zinc and 

 less sulphur than he gives. Had the proportions been 



Zinc, 68 



Sulphur, 32 



100 



the blende would be a compound of 1 atom zinc and 1 atom 

 sulphur. 



That I might acquire some additional information on the 

 subject, I requested Mr THOMAS MDIR *, of whose uncommon ac- 

 curacy as an experimenter I had had ample proof, to analyze a 

 specimen of crystallized blende with which I furnished him. 

 The crystals had the diamond lustre, were blackish, and almost 



* The premature death of this excellent young man, since this paper was written, 

 is an event very much to be deplored. He had wrought as a practical chemist for 

 several years in my laboratory ; and, to much practical knowledge, had added so 

 much neatness and dexterity, joined to uncommon industry, that he would certainly 

 have speedily distinguished himself as a chemist. 



