Examination for Tin.

Tin is readily recognized in Tin Pyrites, by exposing a small piece of the mineral to the oxidating flame, on charcoal. The assay at first exhales a sulphurous acid smell, afterwards becomes snow white on the exterior, and a white coating is perceivable on the support surrounding the specimen; this sublimate is so profuse, that the charcoal is not seen in any part between it and the metallic bead. This deposit is not expelled in either flame; in other respects, its comportment is similar to the oxide of tin.

The tin can be separated from this mineral, in the metallic state, by roasting alternately in the oxidating and reducing flame, then pulverizing the mass in an agate mortar, with double its quantity of a mixture consisting of 100 parts soda, 50 parts borax, and 30 parts silica, and heating the whole on charcoal in the reducing flame, until the tin and copper are reduced to a globule. In this treatment the whole of the copper becomes reduced, but only a portion of the tin, the rest remaining dissolved in the glass with sesquioxide of iron. The cupriferous tin bead, which is friable if too small a quantity of tin is not present, must be separated, and what remains treated with soda in a strong reducing flame, by which means the rest of the tin becomes reduced, and is obtained in particles, by pulverization, and sifting with water. The cupreous globule, when heated upon charcoal with microcosmic salt in the oxidating flame, fuses, and the resulting glass, when cold, has a reddish color, owing to the presence of suboxide of copper.

With the stanniferous Rohstein, the treatment is the same as above. Tin Stone behaves like the oxide of tin, with this difference, that it imparts the color of iron to borax and microcosmic salt, and often affords the manganese reaction with soda on the platinum wire.

The best method for the detection of tin in Tantalites and Tin Slags is by reduction with soda; but in such a case it is necessary to add a small portion of borax, to dissolve the tantalic combinations, and prevent the reduction of the iron. After the completion of such a process, the tin is obtained by pulverization and

sifting. To be convinced that the metallic particles obtained are tin, dissolve protoxide of copper in microcosmic salt, add some of them to the flux, and then heat the whole upon charcoal in the reducing flame. If tin is present, the glass will be colored reddish on cooling.

§ 17. ANTIMONY—Sb-Presence in the Mineral Kingdom, and in the products of Smelting Furnaces.

Antimony is found in nature :

a. Metallic, combined with other metals; namely, with a little Silver and Iron, in Native Antimony [Sb]; with Silver, in Antimonial Silver; and with Arsenic, in Arsenical Antimony;

b. With Sulphur, and Sulphides of other metals; exempli gratia, per se, in Grey Antimony, which generally contains Lead, Copper, Arsenic, and Iron; with Iron, in Berthierite; with Nickel and Arsenic, in Nickeliferous Grey Antimony; with Lead and traces of Iron, Copper, Bismuth, and Zinc, in Jamesonite; with Lead, Copper, and Iron, in Bournonite; with Lead, and a trace of Copper, in Zinkenite; with Lead in Antimonial Lead Glance; with Silver and Copper, in Melan-Glance; with Silver, Copper, and Iron, in Miargyrite; with Silver, in Dark Ruby Silver-Rhombohedral Ruby Blende ;-sometimes with Silver and Arsenic, in Light Ruby Silver; contaminated with Arsenic, Silver, and Iron, in Arsenical Silver; also, more or less, in the following argentiferous minerals: namely, with Silver, Copper, Iron, and Zinc, in Weissgiltigerz and Graugiltigerz; with Copper and Silver, in Antimonial Grey Copper; with Copper, Arsenic, Silver, Iron, and Zinc, in Grey CopperTetrahedral Copper Glance ;-and in a very minute quantity. with Copper, Iron, Silver, and Arsenic, in Kupferblende;

c. As an Oxide, in White Antimony [Sb 03]; which is sometimes contaminated with Sesquioxide of Iron; and with Sulphide of Antimony, in the Red Antimonial Ore [Sb 03 + 2 (Sb, 3 S) ];

d. As Antimonious Acid, in Antimonial Ochre [Sb 04]. Antimony forms a small ingredient in many Argentiferous and

P

This

Plombiferous furnace products, when the smelted or amalgamated ores are not free from Antimonial Silver or Lead Ores. class includes Workable Lead, Amalgamated Metals, and the Abstrichblei, which hold it in a metallic state; further, the Rohstein, Bleistein, Kupferstein, and Lead Rakings, in which it is found as a Sulphide; and the Abstrich, in which it exists as Antimonious Acid, in combination with oxide of lead. Antimony is also met with in Plagionite, Fahlerz, Geokronite, Kilbrickenite, Kobellite, Antimonbloom, Antimonocker, and Romeite.

Examination for Antimony.

The examination for antimony is not very difficult, as it can be detected in most combinations in which it occurs in a metallic state, by two methods; namely,

a. Upon charcoal; when the antimony volatilizes, and the support is coated with a white sublimate; and,

b. In an open glass tube; when antimonial fumes are evolved, consisting of oxide of antimony and antimonious acid, which condense in the upper part. If the treatment occurs with metallic compounds, or metallic sulphides, in which the antimony is to be sought for, as, for example, in the minerals above mentioned, where the antimony is contained as a metal, and in furnace products, the Workable Lead, the raw amalgamated metals, the Abstrichblei, the Roh-, Blei-, and Kupfer-stein, and the Tutty,the examination according to the first method must be performed as follows: A fragment of Workable Lead, raw amalgamated metal, or Abstrichblei, is taken,—the other products and minerals are best employed in a powdered state, and placed in a smooth cavity made in the charcoal, and then submitted to a weak reducing flame. By holding the support in an horizontal position, if any arsenic be present, it will volatilize, if not in combination with nickel, and coat the charcoal with a white or grey sublimate, at a great distance from the assay. Should no arsenic be present, there will be produced a slight deposit of oxide of antimony. When no more arsenical vapor is evolved, the flame is to be directed upon the sublimate, without igniting the charcoal; by

this procedure the whole of the arsenic is expelled, and a clear surface remains, upon which the antimonial deposit is recognizable. If an operator treats a powdered assay in the reducing flame, it may cohere into a bead; but this will only occur when the substance is very fusible. When the latter is the case, the oxidating flame must be brought into action. This deposit is white, when no lead is present, and can be driven from place to place, either by the oxidating or the reducing flame; if the reducing flame is employed, it assumes a slight dark blue appearance, which is characteristic of the presence of antimony. If the substance contains lead, a yellow sublimate of the oxide of this metal is also obtained, which rests at a greater distance from the assay than the antimonial one, and when in thin layers, appears bluish, thus resembling a sublimate of antimony in the same disseminated state. When much antimony is present, the lead does not impede the determination, but if, on the contrary, the sample contains a large amount, an operator must not blow for too long a time upon it; if this precaution be observed, only a white antimonial sublimate results, as the lead is not expelled unless by a long uninterrupted blast. The deposition of lead may be entirely prevented by the addition of some vitrified boracic acid to the substance under examination; when this mixture is acted on in the reducing flame, the oxide of lead formed is absorbed by the boracic acid, while the greater portion of the antimony volatilizes, and coats the charcoal with its oxide. The antimonial lead globule must not be kept in the centre of the molten mass, but only in contact with it, because the antimony, in the former case, is vaporized with difficulty. If the substance contain zinc, a sublimate of this metal is also obtained, which is readily distinguished from that of antimony, by not being volatilized in the oxidating flame.

Minerals and furnace products containing antimony, as an oxide or acid, can also be partly investigated in the above manner, but a distinct sublimate is not always procured; particularly if the oxide of antimony, or antimonious acid, be disseminated or combined with other bodies. When this occurs, the assay should be mixed with soda, and treated on charcoal, in the reducing flame, when the antimony volatilizes and coats the support with

an oxide, which is very distinct, even when a minute quantity of antimony is contained in the sample. If the antimonious acid be in combination with much oxide of lead, which is the case with the Abstrich, the manipulator must not blow for any length of time, so as to prevent the volatilization of much lead. Combinations of oxides of tin and antimony, or antimonious acid, which do not occur in nature, must be treated with a mixture of soda and borax, on charcoal, in the reducing flame. The oxides are reduced and separated in small limpid metallic globules, which must be sifted from the recrementitious particles, and then heated on charcoal, with three times their volume of proof lead, and a small portion of vitrified boracic acid. If the assay be treated in the reducing flame only, antimony volatilizes, and coats the charcoal with a sublimate; the tin oxidizes, and covers the metallic button with a deposit, which dissolves with a part of the lead in boracic acid. The antimonial sublimate is freed from oxide of lead by this procedure, and can therefore be readily recognized. The oxide of tin, which deposits on the molten button, resembles the formation of oxide of nickel upon a nickeliferous lead globule; but as tin and nickel behave perfectly different towards borax, it suffices when the presence of the former is determined.

The second method for the detection of antimony, when in a metallic state in its combinations, is the following:-The substance is heated in a glass tube, whereby the antimony oxidizes and sublimes, forming a white fume, the behavior of which varies, according to the different metals with which the antimony is in combination. If the metals are readily oxidizable, antimonious acid fumes will be expelled, which are very stable, and not acted upon by heat.

The fume which escapes from a silver or copper compound, partly passes off, and partly deposits on the upper part of the tube. That which escapes possesses an acid smell; but, if sulphur happens to be present, the odor of sulphurous acid will predominate.

If the substance contains lead, an exhalation also ensues, which is very dense. The portion which volatilizes may be regarded as pure oxide of antimony; and the nonvolatile portion, as antimonite of lead.