Dehydratioo in Laterite Formation Sherman et aL 
445 
It has been established by Fieldes et aL 
(1952) that the amorphous colloidal hydrated 
oxides have a high cation exchange capacity. 
In a personal communication from these 
workers, they report that they have found 
that the hydrated iron oxides lose cation ex- 
change capacity on dehydration. These ob- 
servations support the findings in this study. 
SUMMARY 
A study has been conducted to ascertain 
the role of dehydration in the development 
of the indurate laterite crust. The following 
conclusions appeared to be justified: 
1. The data obtained from differential ther- 
mal analysis, elemental analysis, and physi- 
cal measurements have established that the 
dehydration of the colloidal hydrated ox- 
ides of the soil is responsible for the de- 
velopment of the indurate laterite horizon 
when exposed to a drying environment. 
2. The dehydration of the titaniferous fer- 
ruginous horizon will increase the bulk 
density and particle density of the soil. 
3. Dehydration causes the development of 
inert dehydrated minerals as shown by the 
data on loss on ignition and cation ex- 
change capacity. The colloidal hydrated 
iron oxide is converted to hematite or 
similar iron oxide minerals. 
4. The rates of dehydration of ferruginous 
layers will probably vary according to the 
mineral content of soil and the vegetative 
and climatic environments. 
REFERENCES 
Aubert, G. 1949. Observations sur le role de 
Eerosion dans la formation de la cuirasse 
lateritique. Bui. Agr. du Congo Beige 40: 
1383-1386. 
1950. Observations of the degrada- 
tion and lateritic-crust formation in North- 
West Dahomey. [Fourth] Internatl. Cong. 
Soil Set., Trans. 3: 127-128. 
Aubreville, a. 1947. Erosion and "bovali- 
zation” in French Black Africa. Agron. Trop. 
2: 339-357. 
1948. Casamance. Agron. Trop. 3: 
25-52. 
Buchanan, H. F. 1807. Journey from Madras^ 
Canara, and Malabar. London. [3 vols., 
reference to vol. 2.] 
Campbell, J. M. I917. Laterite: Its origin, 
structure, and minerals. Mining Mag. 17: 
67-77; 120-128; 171-179; 220-229. 
Chevalier, A. 1948. Degradation and con- 
servation of soil of tropical Africa: Origin 
and extension of laterites and of ferrugin- 
ous shell: Struggle against sterilization of 
African soil. Rev. Internatl. Bot. Appl. 28: 
49-66. 
1949. Points de vue nouveaux sur les 
sols d'Afrique tropicale sur leur degrada- 
tion et leur conservation. BuL Agr. du 
Congo Beige 40: 1057-1092. 
Davis, P. W. 1940. Preliminary note on Nil- 
amber soils with special reference to their 
suitability for teak. Indian Forester 66: 658- 
671. 
Fieldes, M., L. D. Swindale, and J. P, 
Richardson. 1952. The relation of col- 
loidal hydrous oxides to the high cation 
exchange capacity of some tropical soils of 
the Cook Islands. Soil Sci. 74: 197-206. 
Fox, C. S. 1933. Laterite and laterite soil. In- 
dian Forester 59: 630-635. 
Fujimoto, Giichi, G. Donald Sherman, 
and Ada E. Chang. 1949. The chemical 
composition of the separated mineral frac- 
tions of a ferruginous humic latosol profile. 
Soil Sci. Soc. Amer., Proc. (1948) 13: I66-I69. 
Glinka, K. D. 1927. The great soil groups oj 
the world. 150 pp. Edward Bros. Ann Arbor, 
Michigan. 
Harrassowitz, H. 1930. Boden der trop- 
ischen Regionen, Blanch’s Handhuch der 
Bodenlehre 3: 362-436. 
Harrison, J. B. 1933. The katamorphism of 
igneous rocks under humid tropical conditions. 
79 pp. Imperial Bureau of Soil Science, 
Harpenden, England. 
Holmes, A. 1914. Investigations of laterites 
in Portuguese East Africa. Geol. Mag. 6' 
529-537. 
