332 THE MONNIER PROCESS OF REDUCING ORES. 



used for lixiviating each holds 25 tons of ore, besides the water needed to 

 dissolve the sulphates of silver, copjDer and soda. 



"We will now return and see what becomes of the residue of insoluble . 

 matter left in the lixiviating tank. It consists of silica, pure gold and ses- 

 quioxide of iron, also a small amount of silver with sulphate of lead. When 

 the liquid has been drained from it, it is shoveled out on the platform (P), 

 from which it is passed into the surface (14). After mixing with water and 

 thorough grinding it runs into the feeders (15) — which act also as reducers 

 of the remaining sulphate of silver — and thence through wooden spigots and 

 troughs into the broad, shallow and long troughs (16), provided from point 

 to point with boxes or catchers of peculiar construction. The bottoms of 

 these boxes and troughs are covered with amalgamated copper plates. 

 Here the gold is so free it is immediately taken up by the quicksilver and 

 with the remaining silver is secured in the form of an amalgam, while the 

 residuum, containing oxide of iron, passes outside of the building to a large 

 wooden tank. From that the oxide is collected in a still larger tank, where 

 it settles, and is collected and dried. Mixed with oil this oxide of iron 

 makes the purest of metallic paints — its natural color reddish brown — and 

 is the very best that can be used on all iron structures. By combining dif- 

 ferent ingredients with it various colors can be produced. It makes a first- 

 class fireproof roof paint. 



We shall close this description by stating some advantages of sulphatiza- 

 tion over chlorination, as is proved at the Providence mine. 



-By chlorination much of the coarse gold may be lost, and no silver can 

 be saved. SuljDhatization usually saves from 92 per cent, to 95 per cent, of 

 the gold, and leaves it in such a free state that quicksilver takes it up at once. 



To chlorinate gold some 48 hours are generally required. The method 

 of sulphatization requires but 12 hours. Chlorination extracts gold only. 

 This "Monnier method" extracts gold, silver, copper and oxide of iron. Then 

 these better results are obtained at a greater reduction of expense in labor 

 and fuel, and the expense of buying sulphuric acid, manganese and salt is 

 avoided. It takes one man at the roasting cylinder in the Monnier process, 

 and half a cord of wood, in twelve hours, to sulphatize fifteen tons of ore^ 

 when by other processes, such as chlorination, it takes three men and one 

 cord and a quarter of wood for one ton and a quarter of ore. 



The only material purchased in sulphatizing is sulphate of soda at a 

 trifling expense, while the method produces its own sulphuric acid. As has 

 been shown, the soda can be used again and again with scarcely any loss. 



When we remember how rich in sulphurets are the almost exhaustless 

 quartz leads of our mountains, we can scarcely overestimate the value of this 

 successful introduction of Prof Monnier's method on the Pacific coast. 



The Professor inferms me that the application of the revolving cylinder 

 in this method is new and far surpasses expectation. As to the other appa- 

 ratus, it has been brought step by step to its present state of perfection by 

 its use in the Eastern States in the treatment of 14,000 or 15,000 tons of sul- 

 phuret ores. 



