HAWAII AGRICULTURAL EXPERIMENT STATION 
HONOLULU, HAWAII 
Under the joint supervision of the 
UNITED STATES DEPARTMENT OF AGRICULTURE 
AND THE UNIVERSITY OF HAWAII 
BULLETIN No. 62 
Washington, D. C. 
July, 1931 
PHYSICAL PROPERTIES OF HAWAII SOILS 
WITH SPECIAL REFERENCE TO THE 
COLLOIDAL FRACTION 
By Charles Richter, Assistant Chemist 
CONTENTS 
Page 
Introduction 1 
Some facts relative to tropical soil 
formation 2 
Description of soils used in the inves- 
tigation 5 
Certain physical properties of Ha- 
waii soils 11 
Texture 11 
Specific gravity 15 
Moisture relationships 17 
Relation of organic and inorganic 
properties to adsorption 23 
Organic phase 23 
Inorganic phase 24 
Page 
Dispersion of Hawaii soils 26 
Mechanical aspect 26 
Chemical aspect 28 
Estimation of colloids by the water- 
vapor adsorption method 32 
Comparison of the hydrometer and a 
modified pipette method of mechan- 
ical analysis 37 
Summary 40 
Literature cited 41 
Appendix 43 
Physical characteristics of some 
typical and unusual Hawaii 
soils 43 
INTRODUCTION 
The origin, formation, and composition of tropical Hawaii soils 
invest them with physical and chemical properties which vary widely 
and are quite unlike those of the soils of the mainland of the United 
States. In some cases they also differ considerably from those of 
soils of other tropical countries. 
The large amounts of fine material, organic and inorganic, with a 
chemical composition typical of lateritic decomposition, cause condi- 
tions which are radically different from those of other soils and which 
are sometimes extreme in nature. Moisture relationships especially 
exhibit unusual behavior in many of the soils. 
It has long been known that the colloidal fraction of the soil plays 
a significant role in the soil complex phenomena. The investigations 
of the past decade have definitely established the fact that practically 
all the essential properties of soils are directly or indirectly linked with 
the colloidal phase, and that such important processes as flocculation, 
drainage, plasticity, moisture-holding capacity, shrinkage, fixation and 
availability of plant-food elements, hydrogen-ion concentration, and 
base exchange are functions of the colloidal part of the soil. 
The soils of Hawaii, because of the above-mentioned differences in 
origin, formation, and composition, may be logically expected to 
exhibit a difference in the nature of the colloidal complex as com- 
pared with soils of other countries. 
52031—31 1 1 
