CONTENTS. 7 
Tart II. Methods— Continued. Page. 
XII. Titanium— Cod tinned. 
Gooch's gravimetric met hod 71 
Gooch's method not directly applicable to rocks con- 
taining zirconium • 72 
Superiority of the colorimetric and Gooch methods over 
the older ones 73 
Baskerville's method 73 
XIII. Barium (zirconium, total sulphur) 73 
Reasons for estimating barium in a separate portion 
of rock powder 73 
Modes of attack and subsequent treatment 74 
XIV. Zirconium 75 
Author's method 75 
Other methods 76 
X V. Rare earths other than zirconia 77 
XVI. Phdsphorus 78 
Procedure when material is ample 78 
Procedure when material is scanty 79 
XVII. Chromium 79 
Gravimetric method 80 
Colorimetric method 80 
Preparation and strength of standard solution 80 
Preparation of the test solution 80 
Comparison of colors 81 
A few comparative data 81 
XVIII. Vanadium (chromium), molybdenum 82 
Distribution of vanadium and molybdenum 82 
Description of method 82 
Application of the method in presence of relatively much 
chromium 85 
Condition of vanadium in rocks 88 
XIX . Ferrous iron 88 
Comparison of the sealed-tube and hydrofluoric-acid methods ; 
comparative worthlessness of the former in rock analysis. . 88 
The modified Mitscherlich method 90 
Strength of acid 90 
Filling, sealing, and heating of the tube 90 
Reason for introducing gas and sealing as above 
directed 91 
The hydrofluoric-acid method 92 
Pratt's modification 94 
Influence of sulphides, vanadium, and carbonaceous matter 
on the determination of ferrous iron 94 
Sulphides !)4 
Vanadium 95 
Carbonaceous matter 96 
Uncertainties of the ferrous iron determination 96 
XX. Alkalies 96 
The Lawrence Smith method 96 
Treatment of the mineral powder t>7 
Separation of calcium and sulphuric acid 98 
Precipitation of potassium 98 
Lithium 99 
Gooch's method 99 
