Remarks on Assaying Ores of the Precious Metals, and 

 a New Method with the Blowpipe. By Leroy C. 

 Cooley, Ph. D. 



[Read before the Albany Institute, April 19, 1870.] 



Silver and gold have heen known from the earliest pe- 

 riod of which history gives us any account. Much is 

 known concerning the ancient uses of these precious metals, 

 but very little is known of the methods by which they 

 were extracted from their ores. The ancient assay seems, 

 however, to have been conducted on principles not very 

 different from those applied at the present time. Advance 

 in this art has, perhaps, consisted less in the application of 

 newly discovered principles than in the improvement of 

 those already known. 



Ancient methods, correct in principle it may be, but 

 crude and wasteful in their execution, have given place to 

 others more elegant and more exact. 



Among the various methods of extracting precious metals, 

 the assay by solution or the wet assay, as it is generally called, 

 is doubtless the most accurate, and will be chosen whenever 

 analyses are to be made for purely scientific purposes. For 

 commercial or metallurgical purposes, however, the assay by 

 fire or the dry assay is sufficiently exact, and, being in almost 

 universal use, it shall be the only one to which attention 

 need be given on the present occasion. 



The assay by fire may be conducted either by means of 

 the furnace or the blowpipe. The blowpipe furnishes an 

 easy means of detecting the presence of the precious metals, 

 but, for reasons shortly to appear, its use has been for the 

 most part limited to this purpose, and the furnace has been 



