278 MINII^ra INDUSTET. 



the iron was thrown down as a basic salt. The oxide of zinc estimated 

 in the solution was .3250 of a gramme. 



Iron and copper pyrites are but slightly altered by the copper solutions. 

 In practical operations at the mill they are found in the tailings without 

 showing any appreciable signs of having been attacked. 



It will be observed in the above experiments that the argentiferous snl- 

 phurets were always more or less chloridized by the action of the copper 

 salts. 



In order to indicate more clearly the relative amount of decomposition 

 produced by the two chlorides of copper, the results are here brought together 

 as follows : Two grammes of argentite gave .1705 grammes of silver. After 

 treating two grammes of the mineral with chloride of copper, the residue 

 gave .099 grammes of silver; after treating two grammes of the mineral 

 with sub-chloride, the residue gave .1653 grammes of silver : showing that in 

 the former 58.0 per cent., and in the latter, 2.9 per cent, was chloridized. 

 No sulphide of copper was detected in any of the residues examined ; sulphu- 

 ric acid, however, was found in the filtrate in several instances. 



Pan Experiments. — With a view to determine, if possible, some of the 

 problems involved in the action of mercury, common salt, and sulphate of 

 copper, employed in the decomposition of the Comstock ores by the Washoe 

 process, the experiments^ described in the following pages were undertaken 

 upon two lots of ore, whose composition, was well known. 



It was necessary, in order to make the investigations of any practical 

 value, that the material should be treated in such a manner as to imitate as 

 closely as possible the operations carried out on a large scale at the mills, and 

 at the same time to be able to repeat precisely the same conditions as often 

 as desired, and to know the exact results of each trial. 



Of the ores used, one was a lot of first-class rock from the Savage mine, such 

 as is ordinarily sent, on account of its high value and large amount of base 

 metals, to Ball's Mill, for reduction by the barrel-process, as described in a 



1 These experiments were conducted at the Sheffield Laboratory of Yale College. 

 The assistance of Mr. Ellsworth Daggett was obtained, and to his experience in the 

 mechanical details of milling operations, much of the credit in carrying out the work 

 is due. ■ i 



