Professor Whitney communicated the following letter from Professor Brush, giving the results of a chemical investigation of the meteoric iron presented to the city of San Francisco, by General Carleton:
Sheffield Laboratory of Yale College,
New Haven, March 30th, 1863.
Professor J. D. Whitney, State Geologist, San Francisco, Cal.
Dear Sir:—I have examined the specimen of meteoric iron from Tucson, which you sent me for analysis, and herewith communicate to you my results.
The density of the mass is 7.29. When a fragment of it is placed in a solution of neutral sulphate of copper, it quickly becomes coated with metallic copper, proving the iron to be “active.” An inspection of the specimen with a lens showed it to be dotted with little cavities, which on the fresh fracture were lined with a white silicious mineral, giving the surface a porphyritic, or pseudo-porphyritic, appearance.
When a fragment was attacked with an acid, a portion of the iron was dissolved, leaving the silicious mineral projecting from the surface of the specimen; and with a magnifier, black particles of Schreibersite could be seen. After complete solution of the iron, a careful microscopic examination was made of the insoluble residue. With a magnifying power of 25 diameters, it appeared to consist chiefly of two substances: one a milk-white to transparent mineral, having a fused, rounded surface, occurring in little globules, or elongated, rounded particles; while the other constituent was black and angular, and attractable by the magnet. The first named substance, when observed with a magnifying power of 100 diameters, proved to contain minute specks of the black mineral disseminated through it; some of the silicious fragments were translucent and of a milk-white color, and others colorless and transparent; a large number, however, were transparent at one end, shading into milk-white at the other, thus seeming to indicate that the transparent and translucent portions were not two distinct minerals. A blowpipe examination of the silicious mineral showed it to have characters very much resembling olivine. The black mineral proved to be Schreibersite. A minute trace of chromium was also observed in the insoluble residue.
The qualitative analysis of the portion soluble in nitric acid indicated the presence of iron, nickel, cobalt, copper, phosphorus, lime, and magnesia with unweighable traces of chlorine, sulphur, and alumina. For the quantitative examination of the meteorite a fragment weighing 4.3767 grammes was treated with nitro-chlorohydric acid (aqua regia), and after solution of the iron the whole was evaporated; on approaching dryness, gelatinous silica separated, showing that the silicate had been partially, at least, decomposed by the acid. After heating until the silica was rendered insoluble, it was repeatedly treated with acid and evaporated, so as to insure the oxydation of all the Schreibersite, and finally the soluble part was taken up with chlorohydric acid, and on dilution separated by filtration from the silica and insoluble residue.
The filtrate, or soluble part, was accurately measured and divided into four portions for analysis—two portions were used for the determination of the iron, nickel, cobalt, phosphorus, and alkaline earths; a third portion was employed to estimate the copper, and the fourth portion was reserved to answer in case of accident.