obtained pure by this operation; on the other hand, if the portion of nickel be considerable, the globule obtained is still nickeliferous. In this case, it is fused again with its volume of proof lead, and one decigramme of boracic acid; and this operation ought to be repeated with twice the quantity of lead, and one decigramme of boracic acid, if, after the second oxidation, the copper has not lost its white color. The scoria formed in these operations must be of a red color, from the oxide of nickel, and transparent when compressed with the pincers. Green colored transparent scoriæ indicate dissolved oxide of copper; a brownish tinge, with opacity of the scoria, indicates the presence of dissolved suboxide of copper: these colorings, however, only appear when the affined copper is kept fusing too long. Scoria of a brownish-red color ought to be covered with the reducing flame after removing the globule, to reduce the copper; and then obtain it by levigation and lixiviation. The reduction should be continued until the red coloring of the scoriæ has disappeared; on the contrary, if the scoriæ are colored blue by the oxide of copper, it is difficult to deoxidize it, even in the best reducing flame. The copper obtained from this species of scoriæ is generally nickeliferous, and seldom exceeds 0-1 milligramme. If, after these operations, the copper has attained its natural color, its weight is ascertained, in order to calculate the value of the treated alloy. The following examples show that, notwithstanding all precautions, a small loss of copper is sustained in the described treatment; this takes place in the affinage, as well as in the first and second treatment with boracic acid, though it cannot be perceived, owing to the dark color of the scoria: 1. From 50 milligrammes of an alloy of 50 copper, 25 nickel, and 25 zinc, 24.5 milligrammes of pure copper were obtained. In this instance, therefore, there was a loss of 0.5 milligramme 1 per cent. 2. A mixture of 40 milligrammes of granulated nickel, with 10 milligrammes of rasped copper, yielded, in the examination, only 8.6 milligrammes of copper,-loss, 14 milligrammes per cent. = € 2.8 Although many experiments have been performed to discover a shorter and better way for examination, all endeavors have afforded as yet no more satisfactory results than treatment with lead and boracic acid. C. EXAMINATION OF ALLOYS OF COPPER AND ANTIMONY. Among this order are found, particularly, the stibiferous alloys resulting from the examination of Grey Copper and copper ores containing no lead, and those obtained from rich copper ores, by the addition of oxide of antimony. The separation of these metals is easily, and without loss, effected upon charcoal in the oxidating flame. The sample is placed in a cavity prepared on charcoal, and fused by a good oxidating flame, at the greatest possible distance, taking care to direct the flame aside, from time to time, in order to allow more free access of atmospheric air. The antimony volatilizes, the copper remaining pure. If, owing to the high per centage of antimony, the oxidation is continued for a long time, the depth of the cavity increases, so that the flame touches the alloy with difficulty; when this occurs, the process ought to be interrupted, and then continued on a new piece of charcoal. The purity of the copper is recognized by its ductility, by its greenish-blue color in the fused, and its red copper color in the solid state. If the metallic globule does not possess these properties, it must be submitted to a new oxidation. This sort of copper is generally argentiferous; it ought therefore to be examined for silver. The per centage of this metal is then deducted from the weight of the crude globule. d. EXAMINATION OF ALLOYS OF COPPER AND TIN. The compound of copper and tin, obtained by examinations of one decigramme of pure sulphide of tin, bell, and gun metal, belongs to this class of alloys. Boracic acid cannot be employed advantageously to separate tin from copper, not only as it is fused with difficulty, if not in combination with oxide of lead, but also, because it scarcely acts as a solvent upon the tin. Better results are obtained by the use of a flux which combines fusibility with the property of dissolving the oxide of tin. Its composition is as follows, videlicet: Soda, 100 parts, 50 parts, 30 parts. If stanniferous copper is to be examined, about 60 milligrammes of this composition are fused to a ball on charcoal, and placed by the side of the alloy. Of the compound obtained by reduction from one decigramme of sulphide of tin, the whole quantity is taken, while of the bell and gun metal, the quantity ought not to be larger than 45 to 50 milligrammes. The glass bead, together with the alloy, is then fused in the reducing flame, until a rotatory motion ensues; from this the reducing is changed to the oxidating flame, which is so directed upon the glass, that it is protected from the access of air. The metallic globule then begins to oxidize on its surface, and if the oxide of tin, as well as of iron, is present, the latter is dissolved by the glass. During the oxidation of tin, the sample ought to be kept in such a position, that the alloy may always be in contact with the charcoal on one, and with the fused glass on the other side, to prevent an oxidation of the copper. As this glass readily dissolves the tin, the process ought to be continued until it is perfectly saturated with the metal. Saturation is recognized by the formation of cavities in the enamelled glass, near which small particles of reduced tin appear. The solid metal is then removed from the fused scoria, and heated with 60 milligrammes of the above mentioned glass, upon another piece of charcoal, without detaching the small adhering portions of scoriæ, until the color of fused copper appears; at this period, the glass is covered with a pretty strong reducing flame, until it affords the properties of pure copper. It is then removed from the scoriæ, to observe its physical properties, color, and ductility. If it presents the characteristic signs of pure copper, it may be weighed; if not, it ought to be treated again, with 20 to 30 milligrammes of the flux. In an examination of this nature, care must be taken not to oxidize a portion of the copper, together with the tin; if this occurs, the suboxide of copper dissolved in the glass will communicate to it a brownish-red tinge. Such scoriæ must be treated for some minutes with the reducing flame; the copper is thus de-oxidized, combining with the main globule. A reduction of oxide of tin does not so soon take place, if the glass is not oversaturated. In the separation of the last portion of the tin from the copper, a quantity of the latter always oxidizes; which, however, if proper care be taken, does not exceed the average of 0.3 milligramme upon 25 milligrammes. This metal is found in four different states of combination, in Minerals, Ore, Furnace, and Artificial Products,— a. As a metallic alloy; b. As a sulphide ; c. Oxidized with mineral acids ; d. As a pure oxide, or only in combination with organic acids. These four states of combination must be well considered in quantitative examinations with the Blowpipe, as it is sometimes necessary either to change certain substances in antecedent labors, or to separate wholly some constituents, before it is possible to render the lead pure. In substances containing the lead in the state of sulphide, its per centage may be ascertained in two different ways, videlicet-Substances containing other volatile ingredients besides sulphur, as arsenic, antimony, et cetera, are, as much as possible, purified from these bodies by calcination. The roasted sample is then mixed with soda and borax, placed between pulverized charcoal in two clay basins, one of which, serving as the smelting vessel, is covered with a paste of charcoal, next submitted to the reducing flame, in order to de-oxidize the lead, and to scorify the other substances present in the assay. Here the reduced lead is scattered through the scoriæ in granules of different sizes. The second treatment, employed only lately, is more simple, shorter, and likewise leads to exact results. Substances containing sulphides and arsenides, without antimony, are fused, without previous roasting, in a crucible, together with soda, borax, tartaric acid, and metallic iron; here the lead unites to one ball, the earthy and non-reducible oxides undergoing scorification. The description of the first treatment would have been omitted, had it not been for its usefulness in cases where the presence of copper has to be determined. With regard to the quantitative examination for lead, the minerals, ores, furnace and manufactured products may be divided into, a. Such as contain the lead in a state of a sulphide; b. Such as contain it oxidized, and in combination with mineral acids; c. Oxides of lead, either pure or combined with organic acids; a. d. Metallic compounds. EXAMINATION FOR LEAD, IN MINERALS, ORES, AND PRODUCTS COMBINED WITH SULPHUR. First Method. The substances belonging to this class, which can be examined quantitatively for lead by this method, are, among mineralsLead Glance or Galena, Jamesonite, Bournonite, Zinkenite, et cetera; among ores dressed on the great scale-Galena, and all lead ores containing sulphides and arsenides of other metals; and among products of smelting works particularly-bleistein, plombiferous kupferstein, plombiferous flue rakings, et cetera. A decigramme of these substances, reduced to a finely divided powder, should be weighed ; and then freed from volatile ingre |