(3 Pb 3 S + Sb 3 S)]; with Bismuth, and a little Iron and Copper, in Plumbo-Cupriferous Sulphide of Bismuth; with Antimony and a small quantity of Copper, in Zinkenite [Pb S + Sb 3 S]; and with Bismuth, Copper, and a very small quantity of Tellurium and Nickel, in Siberian Needle Ore [Cu S, Bi S+ 2 (Pb S, Bi S) ] ;

c. In combination with Chlorine; as in Chloride of LeadCotunnite, from Vesuvius-[Pb Cl]; and the Basic Chloride of Lead [Pb Cl+2 Pb O], from the Mendip hills of Somersetshire; d. In an oxidized state, with Alumina and Water, in Plomb gomme-Hydrous Aluminate of Lead—[Pb O, 2 Alo 03 + 6 aq] ;

and,

e. As an Oxide, with Acids, partly alone, and partly combined with other Metallic Salts, exempli gratia,

1 With Carbonic Acid, in White Lead Ore-Weissbleierz[Pb O, C O2]; and in Black Lead Ore-Schwarzbleierz,—of the same composition, only containing a small proportion of free Carbon; also in Earthy Carbonate of Lead-Bleierde,-which is mixed with Alumina, Silica, and Sesquioxide of Iron;

2 With Sulphuric Acid, and about two per cent. of Water, in Native Sulphate of Lead [Pb O, S 03];

3 With Arsenic or Phosphoric Acid, and Chloride of Lead, in Brown and Green Arsenical Lead Ores [Pb Cl + 3 (3 Pb 0, As 05)];

• With Chromic Acid, in Prismatic Lead Spar-Chromate of Lead-[Pb O, Cr 03]; with Chromic Acid and Chromate of Copper, in Vauquelinite-Hemi-Prismatic Olive Malachite[3 Cu 0, 2 Cr 03 + 2 (3 Pb 0, 2 Cr 03)];

5 With Molybdic Acid, in Molybdate of Lead-Gelbbleirz— [Pb O, Mo 03];

6 With Tungstic Acid, in Scheelitine-Tungstate of Lead[Pb O, W O3]; and

7 With Vanadic Acid, in Vanadiate of Lead-Vanadiniferous Lead Spar-[2 Pb 0 + Pb Cl + 3 Pb 0, 2 V 03] ;

Further, Lead forms an essential, and also an accompanying constituent in many furnace products :

a. Metallic, combined with other Metals; exempli gratia,

with Silver, in Workable Lead; with Copper, as Plombiferous Black Copper-Bleiisches Schwartzkupfer,—et cetera.

b. In the state of Sulphide, combined with other Metallic Sulphides, as for example: with Sulphide of Iron, in Bleistein; with Sulphide of Copper, in Bleiischen Kupferstein; and, according to the nature of the ores smelted, mixed also with various other Metallic Sulphides, in Tutty, et cetera. Lead is likewise found in Kilbrickenite, Geokronite, Boulangerite, Federerz, Bleischimmer, Plagionite, Kobellite, Weissgiltigerz, Bleihornerz, Bleiglätte, Schwerbleierz, Nussierite, Melanochroite, and Werkblei.

c. In an oxidized state, to which belongs Glätte-Litharge— and the Abstrich, a greyish froth which is raked off the surface of the Workable Lead, in the process of extracting Silver therefrom. The Lead is first melted at a low heat, when the Abstrich, which is composed for the most part of Sulphides of Lead, Antimony, et cetera, separates. Further, the Cupel Grounds saturated with Oxide of Lead, obtained in the refinement of Lead for Silver, which fall in the melting of Plombiferous Schlichs,-metallic slimes obtained in the washing of powdered ores.

Examination for Lead.

The qualitative examination for Lead is very readily performed, in the following manner :

When plombiferous compounds, which are met with in nature and furnace products, are treated on charcoal, in the oxidating flame, they give a sublimate which is very easily recognized. Other easily volatilized metals, which may be in combination with the lead, either fume away entirely, or else deposit an oxide upon the support. The oxide of lead sublimate, which is dark lemon-yellow while hot, and sulphur-yellow when cold, deposits nearer to the assay than the sublimates of some other metallic oxides, namely, those of tellurium, selenium, antimony, and arsenic, and is by this means distinguished. Should zinc also be an ingredient, the sublimate of oxide of lead will probably be contaminated with a quantity of the oxide of this metal, but the sulphur-yellow color of the lead deposit cannot, however, be mis

taken, when the assay has perfectly cooled. Plombiferous sulphur compounds can be examined for lead by two methods. Either by treating them in the reducing flame on charcoal, with a small addition of borax to separate the iron, and obtain a lead sublimate, or by roasting the sample moderately on charcoal, and reducing with soda, when the lead is obtained pure by sifting the assay from carbonaceous matters, et cetera. If the substance contains bismuth, a deposit of this oxide will ensue in the first treatment, but it is darker than the oxide of lead; and in the second a friable metal is obtained, which, when the bismuth is present in an appreciable quantity, is supposed not to be lead. Should this occur, the substance must be smelted with bisulphate of potassa, as given under the head of Bismuth. The sulphate of lead procured in this manipulation is heated with soda on charcoal, by which means the pure metal, and an oxide of lead sublimate is obtained. If much copper had also been present, black copper would result in the second method, but being so dissimilar from the oxide of lead, no mistake could occur in the discrimination.

Combinations of lead with chlorine, and substances which contain the lead in an oxidized state, with other metallic oxides, earths, or acids, must always be treated with soda on charcoal, in the reducing flame. By this means, metallic and oxide of lead are produced, which may be procured on sifting the pyrognostic residue from scoriæ. Should impure lead be obtained by this method, there must have been other metallic oxides present in the specimen; therefore, to insure an infallible test of the presence of this metal, the assay must be treated for a long time in the oxidating flame, when the characteristic lead sublimate is procured.

§ 9. BISMUTH-Bi-Presence in the Mineral Kingdom, and in the products of Smelting Furnaces.

Bismuth is found in nature :

a. Metallic, as Native Bismuth [Bi], which generally contains a very small quantity of Arsenic; with Tellurium, Sulphur, and

a trace of Selenium, in Telluric Bismuth [Bi S + (Bi, Te)]; and also as a small ingredient in a compound of Arsenic, Cobalt, Iron, and a little Copper, Nickel, and Sulphur, with a trace of Manganese, in Bismuth Cobalt Ore, from Schneeberg;

b. In the state of Sulphide, per se, and also in combination with other Metallic Sulphides, namely: per se, in Bismuth Glance [Bi S]; with Copper, in Cupreous Bismuth-Cupriferous Sulphide of Bismuth-[3 (Cu S) + 2 Bi, 3 S]; with Lead, Copper, a little Nickel and Tellurium, in Siberian Needle Ore; and with Lead, Silver, a little Iron and Copper, in Bismuthic Silver;

c. As an Oxide in Bismuth Ochre [Bi O3]; with, probably, traces of Iron and Copper; and also as an Oxide, with Carbonic Acid and Water, mixed with a little Sesquioxide of Iron, Alumina, and Silica, in Carbonate of Bismuth.

This metal sometimes presents itself as a secondary ingredient in many furnace products. It is found, for example, more or less in the metallic state, in many Cobalt Speisses, if the Cobalt Ores employed for the preparation of Smalt are not free from Bismuth. Smalt Silicate of Cobalt-is prepared in a pure state by precipitating Sulphate of Cobalt with Silicate of Potassa. It is manufactured in very large quantities in Saxony.

Examination for Bismuth.

The simplest method for detecting Bismuth in the above-mentioned minerals and Cobalt-Speiss, is by treating those substances which contain bismuth as a metal, with or without sulphur, combined with a small portion of borax, on charcoal in the oxidating or reducing flame; and those which contain this metal in an oxidized state, treated with soda, likewise on charcoal in the reducing flame. The bismuth, which is either already met with in a metallic state, or is reduced by soda, sublimes by degrees, and coats the charcoal with an oxide, which, while hot, appears dark orange-yellow, and on perfectly cooling, citron-yellow.

If the substance at the same time contains much lead, the color of the deposit is lighter, and very similar to the lead sub

limate; this occurs with the Siberian Needle Ore. In such cases, the presence of bismuth cannot be ascertained with certainty by the previous method, and it is necessary to recur to other methods of procedure.

The first is :-The substance is roasted,-if it contains sulphur or arsenic, it is preferable to perform this experiment in a glass tube, to drive these off as much as possible, because it sinters readily on charcoal,-dissolved in microcosmic salt by the aid of the oxidating flame, and the glass treated with tin for a short time in the reducing flame. If the quantity of bismuth is so small that it contains less than a fourth part of the lead present in the substance, the microcosmic salt will be colored, on perfectly cooling, dark grey, and become ultimately opaque. As oxide of antimony produces the same reaction with tin in microcosmic salt, it is necessary that the absence of antimony be ascertained by a preliminary examination of this metal. If the substance, besides bismuth, also contains copper, the microcosmic salt becomes on cooling brownish-grey, nearly black, and opaque.

During the roasting of a substance, very rich with bismuth, in a glass tube, a yellowish-white sublimate is generally formed close to the assay, and even on the undermost part of the tube which melts in a strong flame to brownish orbicles; which, on cooling are transparent, and of a yellow color. This deposit

consists of oxide of bismuth.

The second method is the following, if the bismuth present is exceedingly small, and the lead not distinct :-The substance is well roasted in a powdered state, the heated mass fused in a platinum spoon, with bisulphate of potassa, and the residual matter treated with water in a porcelain basin, over the flame of the lamp, till solution takes place. By this means the sulphate of potassa and other soluble sulphates are dissolved, while basic sulphates of lead and bismuth remain. The supernatant liquor is decanted cautiously, the residue again treated with distilled water, a few drops of nitric acid added, and the whole heated. The sulphate of bismuth dissolves, while the sulphate of lead remains behind. If both salts be then separated by filtration, and the oxide of bismuth precipitated from the solution by micro