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sulphur of silver, the mercury is quickly extinguished, and that a small quantity of silver is obtained by the distillation of the amalgam. We mixed mercury with ore of vitreous silver reduced to powder; and after a contact of 48 hours, there was formed a small quantity of silver amalgam. In this experiment and in the following, we acted on two or three grammes* of mineral, the temperature of the air being from ten to twelve centigrade degreest, and the mixtures having been slightly moistened.

On imitating the amalgamation de patio used in Mexico, and mixing in a cold state sulphur of natural silver, sulphate of iron, muriate of soda and lime, we did not find a vestige of muriate of silver, although the mixture remained in contact for a week; but we obtained it when the mass was exposed for some hours to an artificial temperature of from 30° to 34° centigradet. In the warm regions of New Spain, the tortas exposed to the sun become the most heated, and it is observed that the amal. gamation takes place a great deal slower on the table lands, where the thermometer descends to the freezing point, than in the deep vallies, and in the plains in the vicinity of the coast. It is probable that the muriate of silver

* 30 or 45 English grains. Trans. + Fron: 1 to 53° Fahr. Trans.

Fron $60 60 930 Fahr, Trans.

mu

which is promptly formed at a temperature of 34°, would form in a long space of time at a much lower temperature.

By mixing muriate of soda, sulphate of iron, and mercury in a cold state we obtain muriale of mercury; and this muriate is also obtained when we triturate mercury with muriate of artificial silver. We may easily believe that in the process of amalgamation on a great scale, a part of the mercury is converted into muriate by two distinct ways, viz. by the decomposition of the muriate of silver, and by the immediate action of magistral and salt employed in too great abundance. The lime which remedies the latter mode of action does not carry off in a cold state the sulphur from the silver ; for on mixing sulphur of native silver with lime, sulphur of lime is not formed, though the mixture has been triturated for several days. The lime opposes in a very remarkable manner, the combination of silver with mercury. We observe that the latter is extinguished with difficulty, when we triturate a mixture of lime, sulphur of silver and mercury. In the same manner on forming a paste of silver mineral, salt, magistral, and mercury, and triturating the schlich till the mercury becomes invisible, we see this last metal separate from the metallick flour, and unite in considerable masses whenever lime is added. · Globules of

VOL. III.

mercury, which gradually increase in size, appear wherever the molecules of lime have touched the mixture; and it is from this particular action of the lime, that the azogueros assert it cools the mercury, or prevents the paste from working. .

The muriatic acid, disengaged from the muriate of sodą by the sulphate of iron, attacks the silver, although the latter is found in its mineral in the metallic state. On treating vitreous silver with muriatic acid, we obtain muriate of silver in abundance; and on pouring the same acid on sulphur of natural silver it disengages itself from the sulphuretted hy, drogen. M. Proust observed that the piastres which fell to the bottom of the sea, at the time of the memorable shipwreck of the San Pedro Alcantara, were covered in a short space of time with a crust of muriatę of silver of half a millimetre* in thickness; and I made the same observation during my stay in Peru at the time of the shipwreck of the frigate Santą Leocadia on the South Sea coast near Cape Saint Helen. M. Pallas affirmst that on the banks of the Jaik in Siberia, old Tartar coins have been found converted into muriate of silver by the contact of an earth which is impregnated with muriate of soda. All these

* .0196 of an inch, Trans. 4. † Nordische Beiträge, B. iii. p. 64

facts tend to prove that in many circumstances, muriatic acid acts upon metallic silver.

M. Gay-Lussac and myself succeeded com. pletely in imitating on a small scale the beneficio de hierro, an ingenious process known in Peru since the end of the sixteenth century, and introduced by M. Gellert into Saxony. We perceived that on mixing in a cold state, sulphur of natural silver, salt, magistral, lime and mercury, the amalgam forms in greater abundance when we added to the paste filings of iron. In this case the iron not only serves to decompose the muriate of silver, as in the process of amalgamation of Freiberg, but also to separate the sulphur from the mineralised silver. Leaving in contact for 24 hours sulphuretted silver and filings of iron, the silver was put into such a naked state that we obtained in a few minutes a considerable quantity of silver amalgam. If we pour muriatic acid on the mixture, infinitely more sulphuretted hydrogen is disengaged than we obtain on treating acid sulphuretted silver alone. It is probable that the oxide of iron at the maximum, which is found in the colorados or pacos, and in mineral, mixed with decomposed pyrites, acts in a manner analogous to the filings of iron.

The enormous waste of mercury, which we observe in the American process of amalgama. tion proceeds from several causes which act

simultaneously. If in the process por patio all the silver extracted was owing to a decomposition of muriate of silver by mercury, there would be lost a quantity of mercury which would be to that of the silver in the muriate nearly as 4: 7. 6; for this proportion is that of the respective oxidations of the two metals. Another and perhaps the most considerable part of the mercury is lost, because it remains disseminated in an immense mass of moistened schlich, and because this division of the metal is so great, that the most careful washing is not sufficient to unite the molecules concealed in the remains. A third cause of the loss of the mercury must be sought for in its contact with the salt water, in its exposure to the open air and the 'rays of the sun for the space of three, four and even five months. These masses of mercury and schlich which contain a great number of heterogeneous metallic substances, moistened by saline solutions, are composed of an infinite number of small galvanic piles, of which the slow but prolonged action is favourable to the oxidation of the mercury, and the action of chemical affinities.

The result of the whole of these researches was, that the use of fire would sensibly improve the process of amalgamation. If the minerals treated, were only vitreous silver, filings of iron alone would be perhaps sufficient to render the

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