THE PHILIPPINE 



Journal of Science 



A. Chemical and Geological Sciences 

 AND THE Industries 



Vol. VI. AUGUST, 1911 No. 4 



PHILIPPINE SOILS AND SOME OF THE FACTORS WHICH 

 INFLUENCE THEM. 



By Alvix J. Cox. 



{From the Laboratory of General, Inorganic and Physical Chemistry, Bureau of 



Science, Manila, P. I.) 



The soil, or that part of the land surface of the earth in condition to 

 support and grow plants, is a heterogeneous system of solid, liquid, and 

 gaseous components which react on each other. These reactions are 

 extremely important and, although they have been extensively studied, 

 they are so complicated that much remains to be discovered. In this 

 paper I desire to deal only with the first-named component, its constitu- 

 tion, and some of the factors which influence the soil. An examina- 

 tion of any soil shows that its solid phase is composed of two parts, the 

 inorganic constituents or the fine earthy material, and more or less 

 organic matter. It is very rare for a natural soil to consist of inorganic 

 matter alone, in fact when it ceases to contain organic matter it ceases 

 to be a soil at all and is simply a mass of pure or mixed silt, sand, or clay. 



The inorganic fraction of the soil consists of sand gi-ains, silt, and 

 clay of various degrees of fineness, resulting from the previous decom- 

 position and disintegration of rocks. A large part is still in the mineral 

 condition in which it was originally derived from the parent rock. This 

 may be shown by an examination of the large, practically insoluble 

 residue remaining after the colored compoimds of iron and other weathered 

 portions have been dissolved by the action of hydrochloric acid. It is 

 probably only that portion soluble in water, or in the soil-moisture which 

 contains, besides soluble salts, carbon dioxide and other organic com- 

 pounds derived from the decomposition of vegetable matter, from which 

 the chief inorganic elements of plant food, namely, nitrogen, phosphorus, 

 104660 279 



