XII. Titanium-Continued. Part II. Methods-Continued. Comparison of the sealed-tube and hydrofluoric-acid methods; ILLUSTRATIONS. Page. FIG. 1. Platinum-tipped crucible tongs 2. Radiator for rapid and safe evaporation. 23 24 3. Chatard's form of drying oven for water determinations.. 37 4. Penfield's tubes for water determination in minerals. 39 5. Penfield's fire brick and charcoal oven for use in determining water.. 40 40 7. Modified form of the Gooch tubulated platinum crucible for the deter- 42 8. Details of Gooch crucible for determining water 9. Arrangement during fusion of Gooch apparatus for determining water. 10. Glass tube for determination of water (Jannasch). 11. Glass tube for determination of water in special cases (Jannasch) 12. Apparatus for colorimetric determinations..... 43 44 46 46 70 13. Cooke's apparatus for the determination of ferrous iron 14. J. Lawrence Smith's crucible for alkali determinations.. 93 97 15. Compact form of apparatus for estimation of carbon dioxide. 102 LETTER OF TRANSMITTAL. DEPARTMENT OF THE INTERIOR, UNITED STATES GEOLOGICAL SURVEY, Washington, D. C., July 13, 1900. SIR: I herewith submit, with a request for its publication as a bulletin of the United States Geological Survey, a manuscript dealing in very considerable detail with the subject of silicate rock analysis, with special regard to the practice in the Survey laboratory. It represents, in largely rewritten and much extended form, that portion of Bulletin 148 which dealt with the same subject. The present publication seems fully justified by the demand on the part of mineral chemists for Bulletin 148, the supply of which available for sale has been exhausted. Very respectfully, W. F. HILLEBRAND, Chemist. Director United States Geological Survey. Hon. CLARLES D. WALCOTT, |