230 CHARLES E. MUNROE 



cherry, and quince, in the blossoms of the peach, sloe, and 

 mountain ash, in the leaves of the peach, cherry lam-el, and 

 Portugal laurel, in the young branches of the peach, in the 

 stem bark of the Portugal laurel and mountain ash, and in 

 the roots of the mountain ash, there occur certain glucosides 

 which, through the action of an enzyme in the presence of 

 water, become hydrolyzed, yielding hydrogen cyanide, or 

 prussic acid, as one of the products. 



The first instance of an attempt to apply the solvent 

 action of the cyanides to the extraction of precious metals 

 from their ores or other bodies containing them appears in 

 United States patents 61866 and 62776, issued to Dr. Julio 

 H. Rae, of Syracuse, N. Y., on February 5 and March 12, 

 1867. Dr. Rae claimed the use not only of potassium cyanide 

 as a solvent for the precious metals in the ore, but also of 

 an electric current in precipitating them from the solution, 

 and of rotatory or movable electrodes. This was followed 

 by United States patent 229586, of July 6, 1880, to Thomas 

 C. Clark, of Oakland, Cal., who roasted his ore to a red heat, 

 and placed it, in this condition, in a cold bath containing 

 salt, prussiate of potash, and caustic soda; United States 

 patent 236424, of January 11, 1881, to H. W. Faucett, of 

 St. Louis, Mo., who subjected hot crushed ores, under pressure, 

 to the action of sodium cyanide in solution; and United States 

 patent 244080, of July 12, 1881, to John F. Sanders, of Ogden, 

 Utah, who treated his ore with potassium cyanide and glacial 

 phosphoric acid. But in each of these last three patents 

 the object was to cleanse the gold previous to amalgamation, 

 potassium cyanide having been used for a considerable time, 

 in California and Australia, for removing the coatings from 

 rusty gold in the pan amalgamation process. 



The cyanide process acquired commercial value in 1887, 

 when John S. Mac Arthur and W. Forrest, of Glasgow, Scot- 

 land, applied, on October 19, for their English patent covering 

 the use of dilute solutions of cyanides in the extraction of 

 the precious metals. Later they obtained a patent for the 

 use of zinc as a precipitant in a particular state of subdivision. 



The commercial value of the cyanide process was dem- 

 onstrated by tests made on a large scale, with ore from the 



