Taken with this precaution, the blue substance, B, gave specific gravity 9.58, and the yellow substance, C, specific gravity 8.51. The specific gravity of normal silver, after melting, was found by G. Rose to be 10.5. That of finely divided silver obtained by precipitation is stated to be 10.62.[1]
I believe these determinations to be exact for the specimens employed. But the condition of aggregation may not improbably vary somewhat in different specimens. It seems, however, clear that these forms of silver have a lower specific gravity than the normal, and this is what would be expected.
Chestnut Hill, Philadelphia, May, 1889.—Amer. Jour. of Science.
Watts' Dict., orig. ed., v. 277.
TURPENTINE AND ITS PRODUCTS.[1]
By Edward Davies, F.C.S., F.I.C.
In treating this subject it is necessary to limit it within comparatively narrow bounds, for bodies of the turpentine class are exceedingly numerous and not well understood. In this definite class turpentine means the exudation from various trees of the natural order Coniferæ, consisting of a hydrocarbon, C10H16, and a resin. The constitution of the hydrocarbons in turpentine from different sources, though identical chemically, varies physically, the boiling point ranging from 156° C. to 163° C., the density from 0.855 to 0.880, and the action on polarized light from -40.3 to +21.5. They are very unstable bodies in their molecular constitution, heat, sulphuric acid, and other reagents modifying their properties. The resins are also very variable bodies formed probably by oxidation of the hydrocarbons, and as this oxidation is more or less complete, mixtures are formed very difficult to separate and study.
Turpentine as met with in commerce is mainly derived from Pinus maritima, yielding French turpentine, and Pinus australis, furnishing most of the American turpentine. The latter is obtained from North and South Carolina, Georgia and Alabama. In Hanbury and Fluckiger's Pharmacographia there is a full description of the manner in which the trees are wounded to obtain the turpentine. Besides these there are Venice turpentine from the larch, Pinus Larix, Strassburg turpentine from Abies pectinata, and Canada balsam from Pinus balsamea.