6 CONTENTS. 
Part II. Methods — Continued. Page. 
VI. Silica, separation from alumina, etc 47 
Alternative methods of decomposition 47 
Preliminary remarks 47 
Decomposition of refractory silicates by hydrochloric acid 
under pressure . 48 
The boric-oxide method * 49 
Preparation of the boric oxide 49 
Treatment of easily decomposable silicates 49 
Treatment of refractory silicates 49 
Further treatment after fusion 50 
Possible objections to the boric oxide method 50 
The sodium carbonate method 50 
Purity of the sodium carbonate used as a flux 50 
Precautions in fusing 51 
Treatment after fusion 51 
Subsequent treatment 52 
Drying and testing of silica 52 
Platinum in filtrates 54 
VII. Metals precipitable by hydrogen sulphide 54 
VIII. Aluminum, total iron 54 
Indirect method for aluminum 54 
Precipitation of aluminum, iron, etc 55 
Precipitation by ammonia 55 
Precipitation by the basic acetate method 55 
Ignition of the precipitate 56 
Recovery of silica and possible barium 56 
Estimation of iron in the precipitate of alumina, etc 57 
Without regard to the presence of vanadium 57 
Having regard to the presence of vanadium 58 
Determination of the true value for ferric iron 59 
Methods aiming at the more or less direct estimation of aluminum. 59 
After first removing iron as sulphide 59 
By extraction with a fixed caustic alkali 59 
Direct precipitation of alumina 60 
IX. Manganese, nickel, cobalt, copper, zinc 60 
Manganese and zinc 61 
Nickel, cobalt, copper 61 
X. Calcium and strontium (barium ) 62 
Separation from magnesium 62 
Precipitation and ignition of the oxalates together 62 
Necessity for two precipitations by ammonium oxalate. 62 
Separation of strontium (barium) from calcium by ether-alcohol . 63 
Behavior of barium -'- 63 
Separation of barium from strontium 63 
XL Magnesium 64 
Precipitation 64 
Methods of collecting and igniting the precipitate 66 
Contamination by and removal of barium and calcium 67 
XI I. Titanium 67 
Colorimetric estimation with hydrogen peroxide (Weller's 
method) 67 
Alternative mode of preparing the test solution 69 
The colorimetric apparatus and its use 70 
