18 ON THE REDUCTION OF LIMAILLE. 



and on no account should they be mixed long before 

 required for use. The skittle-pot should be of such 

 size that the mixture does not more than three- 

 fourths fill it ; place the pot in the furnace, then 

 GENTLY raise the fire, and during this part of the 

 process fill the furnace with coke up to the top of 

 the pot. From a quarter to half an hour (according 

 to the quantity submitted to reduction) will be 

 required in order that the fire may h^ gradually raised, 

 and then complete the coking; the fire may now 

 be as fierce as is usual in such operations, and when 

 the heat is reduced low enough to remove the pot 

 from the furnace, the button will be found entire 

 and the whole of the gold gathered, if the operation 

 has been well conducted. 



If I have abstained from giving any relative 

 proportions of limaille and the acids (during the 

 process) in the former part of the paper, it is 

 because I am aware that no general rule exists for 

 the accumulation of the board, and tray or skin 

 products. Some practitioners may be more careful 

 in avoiding extraneous materials than others are, 

 and consequently the limaille submitted to opera- 

 tion will difier in quality; for instance, if chalk 

 be employed at the board, any admixture of it 

 would, in the process, neutralize some portion of 

 the hydrochloric acid, and in that case an average 

 quantity of acid would scarcely suffice. There is no 

 disadvantage in employing a slight excess of acid. 



I have found by experiments that bone-filings 



