in the reducing flame; a white sublimate of subchloride of mercury is procured. If the mercury, however, be combined with sulphur, the substance must be fused with a mixture of soda and chloride of sodium.

As chloride of sodium also yields a white sublimate, per se, on charcoal, in the reducing flame, but which appears later than the sublimate of subchloride of mercury, and then only when the heat is very strong, the behavior of chloride of sodium, per se, on charcoal, should be first studied, before an examination for mercury in this way be undertaken.

§ 14. PLATINUM-Pt-PALLADIUM-Pa—RHODIUM—

-R-IRIDIUM-Ir-OSMIUM-Os-Presence in the
Mineral Kingdom.

These Metals generally occur united together; sometimes, also, with traces of Iron, Copper, and Lead, in Native Platinum, in which Platinum is, however, the principal constituent.

Palladium is likewise found native, combined with a little Platinum and Iridium, along with the Native Platinum, in Brazil.

Rhodium occurs only as an extremely small constituent in Native Platinum.

Iridium occurs native, combined with a little Osmium, along with Native Gold, and Native Platinum, in Russia. It is also found, with a larger proportion of Osmium, in peculiar grains— Osmium-Iridium-[Ir Os], along with Native Platinum, in South America. The quantity of Osmium in Osmium-Iridium varies greatly.

Osmium has been found, as yet, only in the last named compound, and in Native Platinum.

Behavior of the preceding Native Metals before the Blowpipe.

These metals cannot be so separated from one another by the Blowpipe, that each metal may be recognized when treated with borax or microcosmic salt, on a platinum wire or on charcoal,

since they neither oxidize nor dissolve; beads, more or less colored, are in this case obtained; but the color proceeds from the mixed oxidizable metals, namely, from copper, iron, et cetera, which may be readily detected in this way, in such combinations.

If they be fused with lead, and the alloy subjected to refinement in a cupel,-which operation lasts only as long as it affords the difficultly fusible metals-an infusible metallic compound is at length obtained, which contains, proportionably, much lead; but if a sufficiently large grain of gold be added to it, and then refined in a strong heat, a yellowish-white, or even a platinumgrey metallic button, perfectly free from lead, will be obtained, in case too much platinum or iridium is not present in the alloy. If it is not obtained of a fine quality from the cupel, it may be, very readily, with boracic acid, on charcoal, in the oxidating flame.

The alloy of gold, platinum, iridium, rhodium, palladium, et cetera, thus obtained, can only be analyzed in a moist way when it is required to recover the gold. For this purpose it should be dissolved in aqua regia, the solution partly evaporated, diluted with weak alcohol, and the platinum and iridium thrown down from this solution by chloride of potassium or chloride of ammonium, and the gold, by a fresh prepared solution of protosulphate of iron. The latter is obtained in the metallic state, and requires only to be filtered, edulcorated, and fused with a little borax, on charcoal.

Osmium-Iridium is the only compound which can easily be decomposed, and in which osmium may be recognized. When it is strongly ignited in a glass flask, with saltpetre, oxide of osmium is formed, and may be recognized by its fœtid smell, which is similar to that of chloride of sulphur.

§ 15.

GOLD-Au-Presence in the Mineral Kingdom, and in
the products of Smelting Furnaces.

Gold always occurs, in nature, in the metallic state, thus: a. Mixed with other metals, as with, more or less, Silver, in Native Gold; with Tellurium and Silver, in Graphic Tellurium;

with Tellurium, Lead, and Silver, in Yellow Tellurium; with a large quantity of Tellurium and a little Iron, in Native Tellurium; with Lead, Tellurium, a little Copper, Silver, and Sulphide of Lead, in Black Tellurium; in a combination of Selenide of Molybdenum with a little Silver, in Noble Molybden Glance.

b. In metallic Sulphides; namely, in many Iron and Copper Pyrites, but, however, in small quantities. The quantity of Gold in these Pyrites is very different. The Iron Pyrites so widely diffused in Saxony, which lie in contact with the gangues, and which, at the same time, contain Sulphide of Antimony, and finely disseminated Ruby silver, or other Silver Ore, always yield more Gold than those occurring in the same situation in which no Antimony can be detected: the former contains, in a hundredweight, owing to the admixture of Silver Ores, from five to ten ounces of silver, eight ounces of which yield from 0.5 to 0.8 of a grain of Gold; and the latter contain, in the hundredweight, from 0·125 to 0·5 of an ounce of Silver, eight ounces of which yield only from 0.15 to 0.18 of a grain of Gold.-It is better always to control the assay of silver by analysis in the humid way. For assay, fuse 200 grains of the finely pulverized ore with litharge, carbonate of soda, and charcoal, and cupel the produced button on bone ashes. The results are generally a trifle too low. For humid analysis, fuse 100 grains of the ore with about 300 of carbonate of soda; treat the fused mass with water, to dissolve out the soluble chlorides, precipitate by hydrochloric acid, wash the chloride of silver, weigh, and calculate the amount of silver.

Gold Amalgam is the only product of smelting furnaces, extensively occurring, in which Gold forms the principal ingredient.

However, as auriferous Silver Ores are often smelted, Gold is also found as a secondary constituent, in many products obtained in the reduction of silver; more particularly in the following Brandsilber-if the Gold has not been already separated, Blicksilber, Amalgamated Silver, Workable Lead, Black Copper, Bleistein, Kupferstein, and Rohstein.

Examination for Gold.

Native Gold is easily recognized by its peculiar color. The remaining auriferous metals, Pyrites only excepted, should be treated, when the volatile metals are also to be detected, on charcoal in the reducing flame, until an unchangeable metallic button is obtained. With some minerals, exempli gratia, Graphic Tellurium, Yellow Tellurium, and Black Tellurium, a button remains, which, on cooling, possesses the color of gold, and contains the silver present in the mineral. If it should happen that a pure metallic button is not obtained, a little proof lead and borax must be added to the remaining mass, and the whole treated for some time in the reducing flame. The easily reducible metals combine with the proof lead, and, after cooling, can be separated from the gold and silver by cupellation on bone ashes. If the button obtained by cupellation does not possess the color of gold, but appears white, the quantity of gold is less than that of silver, in which case, the button should be placed in a porcelain capsule, a few drops of nitric acid poured on it, and the capsule heated over the lamp.

If the button does not contain more than a fourth part of its weight of gold, it becomes completely black, and then decomposes, the silver being dissolved, while the gold remains in black flakes. When the silver button contains more than the fourth of its weight of gold, it is blackened, but the silver is not dissolved. It is neither blackened nor dissolved, if the proportion of gold to silver is nearly equal in this case the button must be melted with twice its bulk of pure silver, on charcoal, and again treated with nitric acid, by which the mass becomes black, and dissolves; the pure gold being left behind.

Gold Amalgam is treated, first in a flask similar to the Silver Amalgam, in order to drive off the greater part of the mercury, and then on charcoal in the oxidating flame, when a button of pure gold is obtained.

Brandsilber, as also Blicksilber and Amalgamated Silver, are treated, after being refined with a slight addition of proof lead, on a cupel with nitric acid, and examined whether the silver becomes

black, and whether black gold flakes, or black particles, remain after the solution of the silver.

Workable Lead is refined per se, and Black Copper, with an addition of proof lead on the cupel, and the resulting metallic button treated with nitric acid. If the silver becomes black, or if black particles remain after the silver is dissolved, the metals contain gold.

Iron and Copper Pyrites, Bleistein, Kupferstein, and Rohstein, must be first examined for silver, in the same manner as in the quantitative examination. The resulting button of silver is to be placed in a porcelain capsule, containing some hot nitric acid, and quickly examined with a lens, whether it dissolves with a black or white color. In the former case, the substance contains gold; in the latter, it is absent. When a button is not obtained in the examination of Pyrites, it does not follow that gold is not present, as the quantity is often so minute that it cannot be recognized on the cupel with the lens, even from 100 milligrammes of ore. Hence, two or more fragments should be subjected to examination, the resulting Workable Lead concentrated by cupellation, mixed with a little pure silver, and again refined, by which means the gold is combined with the silver, and may be recognized as above, by the black color of the button, when treated with hot nitric acid.

§ 16. TIN-Sn-Presence in the Mineral Kingdom, and in the products of Smelting Furnaces.

Tin occurs in nature in the following minerals:

In combination with Sulphur, and Sulphides of Copper and Iron, in Tin Pyrites; as an Oxide, in Tin Stone-Pyramidal Tin Ore-[Sn 02], which contains traces of Iron, Manganese, Tantalic Acid, and Silica; as a constituent in most Tantalites, and numerous other minerals, containing Titanium and Uranium.

It very rarely occurs in furnace products, unless Tin Ores have been smelted, and then portions of it will be found in the slags. When Tin Pyrites accompany an ore of Copper, and cannot be separated in a pure state by reduction, a quantity of Tin will necessarily be detected in the first products of the copper smelting, particularly in the Rohstein.