Humboldt, Gay Lussac

Bou ingault, Karsten, and several other chemists of note, have offered solutions of the amalgamation enigma of Mexico and Peru. The following seems to be the most probable rationale of the succe ive steps of the proce :— The addition of the magistral (powder of the roasted copper pyrites), is not for the purpose of disengaging muriatic acid from the sea salt ( saltierra ), as has been supposed, since nothing of the kind actually takes place; but, by reciprocal or compound affinity, it serves to form chloride of copper, and chloride of iron, upon the one hand, and sulphate of soda, upon the other. Were sulphuric acid to be used instead of the magistral, as certain novices have prescribed, it would certainly prove injurious, by causing muriatic acid to exhale. Since the ores contain only at times oxide of silver, but always a great abundance of oxide of iron, the acid would carry off both partly, but leave the chloride of silver in a freer state. A magistral, such as sulphate of iron, which is not in a condition to generate the chlorides, will not suit the present purpose; only such metallic sulphates are useful as are ready to be transformed into chlorides by the saltierra . This is peculiarly the case with sulphate of copper. Its deuto-chloride gives up chlorine to the silver, becomes in consequence a pro to chloride, while the chloride of silver, thus formed, is revived, and amalgamated with the quicksilver present, by electro-chemical agency which is excited by the saline menstruum; just as the voltaic pile of copper and silver is rendered active by a solution of sea salt. A portion of chloride of mercury will be simultaneously formed, to be decomposed in its turn by the sulphate of silver resulting from the mutual action of the acidified pyrites, and the silver or its oxide in the ore. An addition of quicklime counteracts the injurious effect of too much magistral, by decomposing the resulting sulphate of copper. Quicksilver being an excellent conductor of heat, when introduced in too great quantities, is apt to cool the ma too much, and thereby enfeebles the operation of the deuto-chloride of copper upon the silver. There is a method of extracting silver from its ores by what is called imbibition . This is exceedingly simple, consisting in depriving, as far as po ible, the silver of its gangue, then melting it with about its own weight of lead. The alloy thus procured, contains from 30 to 35 per cent. of silver, which is separated by cupellation on the great scale, as described under ores of Lead . In this way the silver is obtained at Kongsberg in Norway. The amalgamation works at Halsbrücke, near Freyberg, for the treatment of silver ores by mercury, have been justly admired as a model of arrangement, convenience, and regularity; and I shall conclude this subject with a sketch of their general distribution. IMG:4147767755307473660_illo1121.png:Amalgamation works Fig. 1006 enlarged (241 kb) Fig. 1006. presents a vertical section of this great usine or hüttenwerk , subdivided into four main departments. The first, A , B , is devoted to the preparation and roasting of the matters intended for amalgamation. The second, B , C , is occupied with two succe ive siftings and the milling. The third, C , D , includes the amalgamation apartment above, and the wash-house of the residuums below. And in the fourth, D , E , the distilling apparatus is placed, where the amalgam is finally delivered. Thus, from one extremity of this building to the other, the workshops follow in the order of the proce es; and the whole, over a length of 180 feet, seems to be a natural laboratory, through which the materials pa , as it were of themselves, from their crude to their refined condition; so skilfully economized and methodical are the labours of the workmen; such are the regularity, precision, concert, and facility, which pervade this long series of combinations, carriages, movements, and metamorphoses of matter. Here we distinguish the following objects :— 1. In division A , B ; a , a , is the magazine of salt; b , b , is the hall of preparation of the ores; on the floor of which they are sorted, interstratified, and mixed up with salt; c , c , are the roasting furnaces; in each of which we see, 1, the fireplace; 2, 3, the reverberatory hearth, divided into two portions, one a little higher than the other, and more distant from the fireplace, called the drier . The materials to be calcined fall into it, through a chimney 6. The other part 2, of the hearth is the calcining area. Above the furnace are chambers of sublimation 4, 5, for condensing some volatile matters which escape by the opening 7. e is the main chimney. 2. In the division B , C , we have d , the floor for the coarse sifting; beneath, that for the fine sieves; from which the matters fall into the hopper, whence they pa down to g , the mill-house, in which they are ground to flour, exactly as in a corn-mill, and are afterwards boulted through sieves, p , f , is the wheel machinery of the mill. 3. The compartment C , D , is the amalgamation work, properly speaking, where the casks are seen in their places. The washing of the residuums is effected in the shop l , below. k , k , is the compartment of revolving casks. 4. In the division D , E , the distillation proce is carried on. There are four similar furnaces, represented in different states, for the sake of illustration. The wooden drawer is seen below, supporting the cast-iron basin, in which the tripod with its candelabra for bearing the amalgam saucers is placed. q is a store chamber. At B , are placed the pulleys and windla for raising the roasted ore, to be sifted and ground; as also for raising the milled flour, to be transported to the amalgamation casks. At D , the crane stands for raising the iron bells that cover the amalgamation candelabra.