Year: 1859

metal the accompanying rock of the vein, and to expel most of the volatile metals. The re- sulting metallic product is then smelted toge ther, with certain proportions of lead This mixture is run into cakes, which are then suS jected to species of sweating process under N moderate fire, which causes the greatest quan- tity of the lead in combination with the silver to ooze out of the cakes, leaving these honeytf combed skeletons behind, consisting of the ort ginal material (deprived of its silver) with some lead The silver lead is then refined in the same way as that obtained from the furnace from lead ores. This process ofseparaton has been superseded in most large establishments of the barrel amalgamation

 NO. 2-MExICAN OR PATIO AMALGAMAT1oN <

 No material alteration has been made since, its discovery in the sixteenth century, and it is most remarkable that such complicated pro- cess could have been so far perfected in those times without the aid of chemistry. This pro-. cess is principally used in the Spanish American. countries, and exceently adapted for them, their climate and their sterile plains and barren. mountains, their want of fuel and difficult access for transportation of heavy machinery By far the greatest portion of the silver is reduced by this process. The process is as follows:

 The ore is first freed from any valueless rock, then they are separated and sorted, thence crushed, and finally ground to an impalpable powder, in the rude but we'll known arrastras, or horse-mills This powder is transferred to the Patio" floor closely paved with rocks. It is there spread over circular surfaces of diff ferent sizes, and but eight inches or one foot thick. Here they are mixed with from two to five per cent of salt, first with shovels, and af- forwards by treadng it we'll with horses, mules or oxen. Next day this is renewed for half an hour, and then one-half or one per cent of ma zstral Cooper pyrites) is added, after which mixing is continued These additions are called incorporation. After this, mercury is sprin- kled over, by being poured through canvass bag, after which the whole mass is again well trodden by animals Their treading is resumed every other day, until trial is made in a horn spoon, by washing of the mixture, shows that all the quicksilver has been taken up by the silver It requires generally two more addi- tions of mercury and the necessary mixing of the ores before the silver is all converted into amalgum. This process requires careful watch ing, and skilful, experienced operator. Mag istral has the property of heating the mass; if used in excess, this will be too hot Gas it is called,) if not enough, the mass will be " cold Y" The consequence of the mass being too hot,wi be a loss of quicksilver by conversion into chlo- ride or calomel If too cold, the chemical ac- tion upon the whole process ceases more or less This last is remedied by adding more mazistral, the former state by adding small quantities of lime Simple as this may seem, it is net so ia practice, and requires great deal of expert ence. The quantity of quicksilver used for the ores depends upon their richness In some parts of Mexico, if the ton of ore averages three pounds of silver, about thirty pounds of quick silver is used, of which four pounds or more are invariably lost When the amalgamation in completed that is, when all the silver in the ground ore has entered into combination with the mercury the mass is brought into large vats, where, by process of washing, the earthly par ticles are foated off, while, owing to specific gravity, the silver and mercury remains behind This residue is pressed through canvass bag which permit the passage of the liquid mercury but not of that combined with the silver as amulgam, which remains behind in proportion of six to one per cent of silver. This silver amalgam is subjected in an iron or earthen re. tort to a red heat for some time, which causes the mercury to evaporate, and in this gassy state it is conducted by iron pipes or other con- trivance into a vessel under water, where il condenses, assuming its original liquid form The silver remains behind in beautiful porous f mass, called Plata Pima in Mexico in which shape it is ready for market, or it is run into bars by simple fusion. The whole process, after taking the ground ore into the patio lasts from twelve days to two and three months This difference is caused by manipulation, compo sition of the ores, and the climate. Ores which will consume only twenty days in the summer to be reduced, may require two or three months