PYRITES AND VARIOUS PRODUCTS. 69 



make the following series of experiments. These enable 

 us also at the same time to see whether the methods of 

 analysis usually employed are sufficiently accurate for the 

 purpose. 



The difference between my results and those generally 

 given was so enormorfs, that it was only after many repe- 

 titions that I could believe those now given to be correct. 

 The numbers, however, obtained in the laboratory have 

 been borne out in a great measure by the amounts of 

 arsenic obtained in the manufactured products, the per- 

 centage of arsenic in the latter being evidently out of all 

 reasonable proportion to the percentages given in published 

 analyses of the pyrites itself. The results are arranged in 

 three Tables. 



In Table I. Part i is given the analyses of various spe- 

 cimens of pyrites ; these are extracted from Richardson 

 and Watts' s ' Technology. ' In Part 2 my own analyses 

 are given in full of a few specimens of the same species 

 of ore. 



Table II. gives the amount (percentage) of arsenic in 

 a certain kind of pyrites, in the sulphuric acid manu- 

 factured from it, and in the various products in the 

 manufacture of which the sulphuric acid has been used. 

 Also the amount of arsenic in the chamber- and flue- 

 deposits. 



Table III. is calculated from Table II., giving the 

 amounts in a manner more useful for practical purposes. 



In order to obtain a proper sample, a good deal of care 

 was taken to get what might be considered a fair average 

 of the ore. 



Forty specimens of the pyrites to be examined were 

 taken from various parts of the lode ; these were reduced 

 to a fine powder, intimately mixed and dried. A portion of 

 this was weighed out for analysis ; I then concluded that 

 the sample might be considered a very fair average one. 



