336 BULPHtfRET OF LEAB, COPPER, AND ANTIMONY. 



before the Royal Society my first paper on endellion, 

 being desirous of obtaining some additional data with re- 

 spect to the proportion in which sulphur enters into the sul- 

 Analysed by phuret of copper, I requested the favour of Mr. Chenevix 

 Mr. Chenevix. t ass } s t me in my researches, by analysing different varieties 

 of the sulphuret of this metal, with specimens of which I 

 furnished him. This able chemist found in one perfectly 

 pure Cornish specimen, which was regularly crystallized, 

 19 of sulphur and 81 of copper ; a proportion exactly simi- 

 lar to that given by Klaproth, if we consider that the sul- 

 phuret of copper analysed by him contained 2*25 of iron, 

 and 0-75 of silex, which did not exist in that analysed by 

 Mr. Chenevix. 

 Other sped- This gentleman at the same time, at my request, took the 

 b^him" 3, ySC * rou ble to analyse seven other varieties of sulphuret of cop- 

 per; I having supplied him with the specimens, duplicates 

 of which I preserved. One of them only was from Bohemia, 

 and the rest from Cornwall. All of them contained from 

 0*03 to 0*08 of iron, but no other extraneous substance. 

 They all gave similar results as to the proportions of sul- 

 , phur and copper, except that the quantity of sulphur was 



a little greater where the quantity of iron was greater. 

 Mr. Smithson's Thus it appears to me incontrovertible, that thepropor- 

 roneous° nS ? '~ t ' on °*" sul P nur 5 admitted in the paper in question as essen- 

 tial to the composition of sulphuret of copper, is much too 

 great; and that the proportion of sulphur, there said to en- 

 ter into the composition of sulphuret of antimony, is too 

 small : which would totally overturn the proportions, by 

 which the author of that paper endeavours to prove endel- 

 lion to be produced by a binary combination between sul- 

 phuret of lead, and the gray sulphuret of copper named 

 fahlertz. It is possible, for this sometimes happens in me- 

 tallic sulphurets, that Messrs. Klaproth and Chenevix, in 

 the specimens they analysed, may accidentally have met 

 with varieties of sulphuret of copper, in which sulphur was 

 superabundant, or simply interposed ; and in this case their 

 analyses will give too large a proportion : but that two 

 chemists, so eminent for their talents as the gentlemen just 

 mentioned, should constantly find the proportion of sul- 

 phur in this sulphuret much less than is assigned in that pa- 

 per, 



