AMALGAMATION. 



17 



easy to ho scon how a complete roasting can bo 



1 l.y it. Probably the most successful 



apparatus or t'urnnce for roasting, will bo the 



lied Torraee furnace, substantially a rectan- 

 gular prismatic- room, with a large number of 

 . tire-clay arranged in such a manner 

 that \ ill 1'all from one to- tho two 



i and so on, until it reaches tho 

 part of tho furnace, from whence it is 

 Tho furnace is heated first by a 

 temporary hearth, but the combustion of the 

 Htilplmr produces afterwards enough heat to 

 keep tho ore constantly in a temperature fit to 



1 the sulphur from the same. Another 



<>d has been proposed, and we believe 

 with much success. It is the invention of Mr. 

 Monnier, and consists in calcining the ore in 



iieratory furnaces with an addition of sul- 

 phate of soda. The whole is calcined at a low 

 temperature, and during the operation the sul- 

 phurcts of iron and copper are at first oxidized, 

 but partly changed into sulphates during the 



.ours of the calcination. These sulphates 

 can be leached out, and, so far as the copper is 

 concerned, it can be won by a precipitation 

 with metallic iron. Tho remaining ore, after 

 tho lixiviation of all soluble salts, is chiefly com- 

 posed of peroxide of iron and the ganguo or 

 quartzoso substances which were in the ore; 

 the whole containing the gold well disclosed and 

 ready for the attack of tho quicksilver. An ad- 

 vantage in this process is the small quantity of 

 fuel needed, and more especially the soft state 

 of every particle of peroxide of iron, which 

 allows an easy access of tho mercury to the 

 most minute parts. 



In many mines the vein-matrix is composed 

 of quartz, which lias bath free metallic gold, 

 and auriferous pyrites. In such cases the ore 

 is often treated with mercury in the raw state, 

 or it is at least passed over copper plates, which 

 are alloyed or amalgamated, and retain all the 

 free particles of gold, after which the ore is 

 calcined and amalgamated. 



Should the ore have too much copper pyrites 

 and zinc-blende or galena mixed with the quartz 

 and iron pyrites, it becomes often too difficult 

 and expensive to apply amalgamation, and the 

 treatment by smelting is preferable. 



Tho groat improvements in desulphurizing 

 pyrites, by which so great quantities of gold are 

 saved, have given an impulse to an active and 

 profitable mining system in several of tho Terri- 

 tories, especially in Colorado. 



A peculiar method of amalgamation for gold 

 ores has lately been put in practice by a Mr. 

 Wykolf, which he calls tho " chloride of sodi- 

 um " process. The machinery used consists of 

 a wooden cylinder, combined with a shaking- 

 table, with the ordinary mechanical appliances 

 for working them. The process itself is as fol- 

 lows: Two hundred pounds of finely-crushed 

 ore is put into tho cylinder or amalgamator, 

 with about one hundred pounds of mercury 

 xty gallons of water, to which three per 

 cent, of salt is added. The cylinder is then set 

 VOL. vi 2 A 



in motion, rocking forward and backward, 

 while steam is introduced by means of a tube. 

 and in about eight minutes the water boils, and 

 the mercury permeates the entire mass. After 

 so working for forty-five minutes, a stream of 

 cold water is let in, which suddenly cools the 

 mass and precipitates the mercury. The gate 

 at the end of the cylinder is then opened and a 

 stream of water run through the cylinder, nn- 

 til it comes clear, when the gate is closed and a 

 new charge is put in. The shaking-tables are 

 merely to collect small particles of metal, which 

 may have been thrown from the cylinder by 

 the force of the water. Mr. Wykoff claims 

 to be very successful with his method, and 

 to save in this way nearly all tho gold con- 

 tained in the ore. 



The 'amalgamation of silver ores is much 

 more complicated, and requires more skill and 

 experience for a successful and economical 

 treatment than the gold ores. In order to ex- 

 plain the theory of this process, it is deemed 

 necessary to remark, first, that the silver ores 

 which are subjected to this treatment are gen- 

 erally sulphurets, arseniates, and antimoniates 

 of silver, or compounds of these bodies. The 

 older theory was, and is yet accepted by many 

 authorities, that these sulphurets, when brought 

 together with common salt (chloride of sodium) 

 and sulphate of copper, under proper condi- 

 tions, are changed into chloride of silver, and 

 that tho subsequent contact with mercury would 

 decompose these chlorides into metallic silver, 

 which forms an alloy with the quicksilver, 

 while another part of the latter takes up the 

 second atoms of chlorine, and forms proto- 

 chloride of mercury, or calomel, which is lost. 

 Another theory is that of Mr. Bowring, who 

 endeavors to prove that the deuto-chloride of 

 copper, produced by chemical action from com- 

 mon salt and sulphate of copper, is changed, in 

 contact with mercury, into a proto-chloride, 

 and the latter, under tho influence of atmos- 

 pheric air, to oxi-chloride of copper, which, in 

 its turn, gives a part of its oxigen to the sul- 

 phurets of silver, producing metallic silver, 

 and leaving again proto-chloride of copper and 

 sulphuric acid as products of decomposition. 

 It will thus be seen how many chemical actions 

 come into play in these processes, and how im- 

 perfectly they are understood yet. It may be 

 said that during tho last few years many 

 experiments were made to improve the amalga- 

 mation of silver ores, especially in Nevada, 

 where, amongst a great deal of quackery and 

 absurdity, several inventions of some merit 

 were introduced. 



Under nearly all circumstances it is necessary 

 to roast the ore, previous to its further treat- 

 ment, with an addition of salt (chloride of 

 sodium). An exception to this rule forms the 

 method introduced by a Mr. Smith, who amal- 

 gamates with but few chemical agents, except 

 common salt, the sulphurets of silver, found in 

 the Comstock Lode, and some other mines. 

 The apparatus he uses is known under the name 



