CONTENTS. 
Page. 
Letter of transmittal 9 
Prefatory note 11 
Experiments relative to the constitution of pectolite, pyrophyllite, calamine, 
and analcite, by F. W. Clarke and George Steiger 13 
The constitution of tourmaline, by F. W. Clarke 26 
The colorimetric estimation of small amounts of chromium, with special 
reference to the analysis of rocks and ores, by W. F. Hillebrand 37 
Volumetric estimation of vanadium in presence of small amounts of chromium, 
with special reference to the analysis of rocks and ores, by W. F. Hille- 
brand 44 
Distribution and quantitative occurrence of vanadium and molybdenum in 
rocks of the United States, by W. F. Hillebrand 49 
Warning against the use of fluoriferous hydrogen peroxide in estimating 
titanium, by W. F. Hillebrand 56 
Mineralogical notes, by W. F. Hillebrand 57 
1. Calaverite from Cripple Creek, Colorado 57 
2. Tellurides from California 60 
3. Hessite from Mexico 63 
4. Covellite aud enargite from Montana 63 
5. Tysonite and bastniisite 64 
6. Prosopite 66 
7. Jeffersonite 68 
8. Anorthite and epidote 69 
9. Roscoelite 70 
10. Mariposite 74 
11. Two sulphates from Montana 75 
On the chloronitrides of phosphorus and the metaphosphimic acids, by H. N. 
Stokes 77 
1. On tri- and tetraphosphonitrilic chlorides 77 
2. On trimetaphosphimic acid and its decomposition products 89 
3. On tetrametaphosphimic acid 116 
4. The higher chloron itrides 124 
5. The higher metaphosphi mic acids 136 
On a hydromica from New Jersey, by F. W. Clarke and N. H. Darton 154 
The alkaline reaction of some natural silicates, by F. W. Clarke 156 
The solubility in water of certain natural silicates, by George Steiger 159 
Index 161 
5 
