The mineral contains, therefore,— Hydrofluoric acid, Sulphuric acid, Chlorine, very little; in still smaller proportions; Lime, a large quantity; Alumina, in small quantity; Soda, apparently only in small quantity; Water, a little, probably only mechanical. These constituents consequently show that the problematical mineral is a combination of phosphate of lime with phosphate of alumina, carbonate of lime, sulphate of lime, fluoride of calcium, and chloride of calcium. 14. Chloride of Sodium-Na Cl. When heated in a glass tube, it decrepitates, giving traces of water, which were mechanically held between the layers of the crystals. On platinum wire, it tinges the flame intensely yellow. With a saturated copper bead of microcosmic salt, it colors the flame of a deep azure-blue, indicative of the presence of chlorine. 15. Borax-Na O, 2 B 03 + 10 aq. It intumesces in the heat, giving off a large quantity of water. When exposed on the platinum wire to the flame, it tumefies strongly, lastly giving a colorless bead. The flame is tinged. yellow. Boracic acid is detected as follows:-Mix borax, sulphuric acid, and alchohol together, and ignite. A green flame indicates the presence of boracic acid. 16. Phosphate of Lead. This mineral is readily distinguished, when in the solid state, by its external characters. In this case it is only necessary to subject it to direct examination for its known constituents. If it be in the state of powder, however, it may be easily confounded with other minerals of the same color, and it should, therefore, be examined in the following manner :— It should be first tested on charcoal in both flames, and its fusibility, and other characters from which a conclusion may be drawn, examined. The powder fuses to a bead, on charcoal, in the oxidating flame, which crystallizes during refrigeration, and becomes of a dark color. If any substance is observed to volatilize during the fusion, and deposit in part on the charcoal as a white sublimate, which admits of being driven further from the assay on the application of either flame, antimony is probably present. A separate test for antimony need not, however, be undertaken on this account, as other compounds may be present which would yield a white sublimate, and which may be accidentally discovered during the course of investigation. If the bead be treated long enough with a strong blast in the reducing flame, the charcoal will be seen to be yellow, as when coated with oxide of lead; and if the blast be discontinued, the bead crystallizes almost instantaneously, during the refrigeration; large facets of an almost white color, similar in brilliancy to mother-of-pearl, being formed. As this appearance is peculiar to phosphate of lead, and as a sublimate of lead was already obtained on the charcoal, it is not necessary to test for the presence of phosphoric acid and lead. It may however be done, in order to be perfectly convinced. A globule of phosphide of iron and metallic lead may be readily obtained with boracic acid and iron, and a button of lead with soda on charcoal, which may be tested for silver by cupellation on bone ashes. The appearance of a white sublimate when the mineral is treated per se on charcoal, is readily explained by the fact, that the natural combinations of phosphoric acid with oxide of lead always contain chloride of lead, which volatilizes. A separate test for chlorine, with a microcosmic salt bead saturated with oxide of copper, shows very clearly that the mineral contains chlorine. 17. Nickel Ochre. This mineral may be easily determined to be a metallic salt. Its constituents are also readily recognized during the course of the examination. It yields some water when heated per se in a bulb tube, its color becoming darker. Its behavior per se on charcoal is then to be examined. It sometimes diffuses an evident alliaceous odor when treated in the oxidating flame, and by treatment in the reducing flame it fuses, with the escape of some arsenic, to a black brittle metallic button, which is readily attracted by the magnet. From this property, and from the mineral possessing a green color, it may be considered with a degree of certainty that it principally consists of arseniate of oxide of nickel. But as natural arseniate of nickel is not always free from oxide of cobalt, oxide of iron, and sulphuric acid, it should be tested with borax, and a separate examination made for sulphuric acid. It dissolves readily in borax, and yields a glass which is violet while hot, and reddish-brown when cold-oxide of nickel. If this glass be treated on charcoal in the reducing flame until all the nickel is precipitated, the glass will appear perfectly colorless when the mineral is free from cobalt and iron; if not free from these, it will appear blue from cobalt, or green from iron. The blue glass may, however, contain iron also; it is, therefore, necessary to fuse it, after being freed from reduced metallic particles, in the loop of a platinum wire; treat it for some time in the oxidating flame, and carefully observe whether it appears green or blue while hot; if the former is the case, it is not free from iron. It is exceedingly difficult to separate completely, particles of reduced nickel from a glass from which the nickel has been thrown down in the metallic state; this is, however, easily effected if the precipitated nickel be melted with a particle of lead, and the glass treated in the reducing flame only. The nickel thus combines with the lead, forming a readily fusible alloy, from which the glass may be removed while in the molten state. The examination for sulphuric acid is made by fusion with soda and borax on charcoal in the reducing flame, and the fused assay treated on a moist piece of silver. 18. Wolfram. The behavior of this mineral before the Blowpipe, as well per se on charcoal, as with fluxes, must be first determined, in order to be able to ascertain the principal constituents, unless the mineral is recognized from its physical character as wolfram. It decrepitates when heated in a bulb tube, and gives very little water. Its fusibility must then be examined. This operation is most conveniently performed in the forceps, in order to be able to observe, at the same time, whether the exterior flame is colored. It fuses with difficulty to a bead, on charcoal, without producing a sublimate; the surface of the bead presents small eminences, from a number of laminated crystals of a considerable size. The mineral should now be tested with borax and microcosmic salt. Borax dissolves it in the oxidating flame, without difficulty, to a clear glass, which is reddish-yellow while hot, when the quantity present is extremely minute, and pure yellow during the refrigeration, as when colored with oxide of iron; from a larger quantity, it appears blood-red while hot, and reddish-yellow on refrigeration. Treated for a few moments in the reducing flame, the tint becomes lighter, showing the color to be derived from oxide of iron only. It is readily dissolved by microcosmic salt in the oxidating flame, to a clear glass, which appears reddish-yellow while hot, and somewhat lighter during the refrigeration; its appearance, however, shows only the presence of oxide of iron. If the glass be treated in the reducing flame, it becomes dark red; even when the quantity present is moderate, it becomes opaque. If a small quantity of the saturated glass be treated with tin on charcoal, for a few moments, in the reducing flame, it will assume a green color when cold. If such a glass be exposed for some time to a strong blast in the reducing flame, the green color dis appears, and a slight reddish-yellow tint remains behind, which undergoes no further change. From these reactions with borax and microcosmic salt, we may conclude that, as the borax glass assumes a redder tint after being treated with the oxidating flame, and a more or less yellow color, when treated for a short time in the reducing flame, the mineral must contain manganese as well as iron; and as the microcosmic salt bead becomes dark red, when treated in the reducing flame, and assumes a green color on the addition of tin, which becomes reddish-yellow when exposed for some time to the reducing flame, tungsten must be present, as well as iron and manganese. If the powdered mineral be fused with soda in a platinum spoon, the fused mass dissolved in water, and hydrochloric acid added to the clear solution, a white precipitate is produced, which, on heating the whole, becomes of a beautiful lemon-yellow color, and may be recognized as tungstic acid. The constituents of Wolfram therefore, are tungstic acid, protoxides of iron and manganese, and a little water. The color of the mineral shows that the iron and manganese are present as protoxides, and not as sesquioxides. B. ALUMINATES. As the number of aluminates which occur in nature is very limited, and we have already treated of the most of them, when speaking of the examination for Magnesia and Alumina, a single example will suffice. Spinelle, red, from Ceylon. The first thing to be done, is to ascertain its behavior before the Blowpipe, both per se, and with fluxes. Heated strongly in the apex of the blue flame while held in the forceps, it loses its form, but communicates no color to the exterior flame. If the thoroughly ignited fragment be viewed with reflected sun light, it appears almost black and opaque, |