324 G. p. MEHHILL — DISINTEGRATION OF GRANITIC ROCKS. 



L 11. II r. 



SiOa 70.47 69.23 69.10 



AlA 14.56 16.18 16.07 



TiOa 0.31 



FeO 3.66 1.75\ . ^. 



FeA 1.95 r '^^ 



CaO 3.27 3.24 2.76 



MgO 2.49 2.86 2.77 



Na,0 2.74 2.68 2.23 



K2O 2.71 2.11 2.10 



PA 0.10 .... 0.06 



100.00 100.00 100.01 



An apparent loss of 1.37 per cent of SiO.^ ; 0.040 per cent of CaO ; 0.51 

 per cent of NagO ; 0.61 per cent of Kfi, and 0.04 per cent of P2O5, or not 

 quite 3 per cent of the total constituents, and a corresponding propor- 

 tional increase of the less soluble alumina, iron and magnesia, is all the 

 change indicated by a purely chemical, bulk analysis. It is evident that 

 here the chief alteration in the conversion of the barren rock into arable 

 soil is physical, attended probably with a partial change in the mode 

 of combination of the various elements. 



ANALYSES OF MATERIAL SEPARATED BY SOLVENTS. 



In order to ascertain what this possible change in combination might 

 be, samples of the soil were treated for a period of ten days with (1) cold 

 distilled water ; (2) cold distilled water through which carbonic acid 

 gas was kept bubbling ; (3) acetic acid, and (4) hydrochloric acid of one- 

 fourth normal strength — that is, one part of acid of the specific gravity 

 of 1.20 to three parts of water. Five hundred grams were used in each 

 of the first three cases and 50 grams in the fourth. The results obtained 

 were as follows : 



The pure water extract (1) amounted to but 0.069 grams (0.0138 per 

 cent), which yielded, qualitatively, reactions for potash and soda and a 

 bare trace of lime, but no iron, alumina or silica. The carbonic acid ex- 

 tract (2) yielded 0.0985 grams (0.0197 per cent), which gave reactions for 

 lime, potash, soda, alumina and iron, but no appreciable amount of silica. 

 The acetic acid extract (3) yielded Professor Packard the quantitative 

 results below : 



K2O 024 grams = .0048 per cent. 



NaaO 007 " = .0014 



FeA 106 " = .0212 



AI2O3 129 '' = .0258 



MnO 047 " = .0094 



CaO 079 " = .0158 



MgO 019 '^ = .0038 



.411 " = .0822 



