A. B. Lyons — Composition of Hawaiian Soils. 421 



Art. LX. — Chemical Composition of Hawaiian Soils and 

 of the Bocks from which they have been derived ; by A. B. 

 Lyons, F.C.S., Honolulu, H. I. 



The relation in chemical composition of soils to the rocks 

 from which they have been definitely derived, can be studied 

 most easily and profitably in a volcanic country, where disinte- 

 gration of the rock is rapid and is attended with great chemi- 

 cal changes. I wish to present, as briefly as is consistent with 

 clearness, the result of studies in this field which I have had 

 occasion to make during the past two years. The chemical 

 composition of these volcanic soils is peculiarly interesting and 

 full of surprises to one unaccustomed. to their vagaries. 



The agricultural analysis of a soil is, of course, not exhaust- 

 ive. The mineral constituents determined are merely those 

 extracted from the finer portion of the soil by the action for a 

 definite time of a specified solvent, generally of hydrochloric 

 acid, of sp. gr. 1*15. The solvent is commonly allowed to act 

 from three to five days. I found by ^experiment that the boil- 

 ing acid would extract from the fine soil practically all that is 

 soluble in two hours, except in the case of some of the very 

 new soils, and in the analyses here reported this method of 

 extraction was adopted, except in the first two, where a longer 

 time (three days) was taken. In the estimation of phosphoric 

 acid, however, nitric acid was used as a solvent, according to 

 the usual practice. The residue after treatment with hydro- 

 chloric acid was found to consist almost wholly of silica and 

 titanic acid. It contained little iron, calcium or magnesium, 

 but retained considerable potassium and sodium, sometimes as 

 much as eighty per cent of all present in the soil. These facts 

 must be borne in mind in making comparisons of the soil 

 analyses with the complete and exact analyses I have to 

 report of the rocks from which the soils have been derived. 



In order to bring out clearly the comparison between soil 

 and rocks, I have reported the mineral constituents only of 

 the soils in per cent, of the weight of the ignited sample. I 

 have added, however, at the foot of the table figures indi- 

 cating the percentage loss on drying at 100° C, and further 

 on ignition of the air- dried soil. 



Out of a large number of soil analyses I have selected for 

 tabulation some that may be considered representative. The 

 :first three are soils derived from decomposition of volcanic 

 sand or ash, spread over the surface of the country by explo- 

 sive eruptions so recent that only the finer particles have suf- 

 fered disintegration. These soils are sandy or gravelly, almost 



