124 SILVER-LEAD DEPOSITS OF EUREKA, j!*EVADA. 



Results. — From these experiments it will be seen that the largest amount 

 of silver was obtained from the method employed in (a), and that the addi- 

 tion of borax increased the quantity of silver where charcoal was not used 

 as the reducing agent. It is probable that the effect of the borax was 

 merely a mechanical one, facilitating the settling of the minute particles of 

 lead by rendering the slag more liquid, and that it had no reducing power 

 on the silver in whatever form that metal may have been. In all these 

 assays two hours were occupied in melting, and the lead buttons were 

 cupelled at the lowest possible temperature. 



Experiments in reducing agents. — Several experiments were made to determine the 

 best reducing agents, and bitartrate of potash was found to give better 

 results than any other. Upon the application of heat this substance is 

 decomposed into carbonate of potash and carbon, both of which act ener- 

 getically upon the substances to be reduced. Borax in the presence of 

 strong reducing agents never takes up silver, even when it is used in con- 

 siderable quantity. 



composition of flux. — The following is the composition of the flux used with 

 377.09 grains of the limestones of Eureka District: 



Grains. 



Litharge 770 



Bicarbonate of soda 5S0 



Bitartrate of potash 165 



Borax 400 



With but slight modifications this flux answers for- almost any coun- 

 try rock. 



weights used. — The weight adopted for the assays of the Eureka rocks, as 

 well as those of the Comstock made for Mr. G. F. Becker, was 577.09 grains. 

 Grains were employed instead of grams, as they correspond with the 

 ( )ertling assay weights used, with the latest improved Becker balance, and 

 377.09 of them were taken, as the .02-grain rider then represented 10 cents 

 to the ton (0.000265) for every division of the balance beam. The values 

 were calculated in cents to the ton of 2,000 pounds, as is usually the case 

 on the Pacific slo t je, but they are also given in percentages. 



Time and manner of melting. — In order to obtain the maximum results it was 

 necessary to melt the assays for nearly two hours. This was accomplished 



