Dec. 2, 1918 Relation of Inorganic Soil Colloids to Plowsole 



515 



matter also counteracted the deflocculating efiFect of the nitrate. The 

 barley was more effective in these respects than the other organic sub- 

 stances. Organic matter showed p,o consistent effect on the flocculating 

 effect of sulphur and gypsum. In the sandy-loam soil it is apparent 

 that the addition of lime to the organic matter had but little effect in 

 decreasing the inorganic colloid matter. 



The action of the sulphur in flocculating the colloid matter is probably 

 due to the formation of sulphates, wliich are good colloid precipitants. 



Groves that had been in cultivation many years contained a much 

 greater percentage of colloid suspension than the corresponding native- 

 soil type adjoining. 



The composition of the colloid suspension obtained from soils differ- 

 ently treated was partially investigated. The colloid was obtained as 

 previously described, precipitated, ignited, weighed, and fused with 

 anhydrous sodium carbonate in platinum crucibles. The resulting cake 

 was taken up with distilled water and partially analyzed. 



The soils used in these determinations had been treated as shown in 

 Table IX, put into flowerpots, and irrigated and cultivated intermit- 

 tently for over a year before these determinations were made. 



Table IX. — Partial analysis of whole soil and of inorganic colloid suspension obtained 

 from same soil receiving certain organic and inorganic treatments. Clay-loam soil from, 

 near Riverside, Cal., of granitic origin 



Soil treatment. 



Colloid 

 in soil. 



silicon 

 dioxid. 



Ferric 

 ox id. 



Alumi- 

 num 

 ox id. 



Cal- 

 cium 

 ox id. 



Manga- 

 nous 

 oxid. 



Phos- 

 phorus 

 pen- 

 toxid. 



Untreated 



3 per cent of manure 



3 per cent of manure -f- 3 per cent of 



calcium carbonate 



3 per cent of manure -f- .2 per cent 



of sulphur 



3 per cent of manure -|- .2 per cent of 



sodium nitrate 



3 per cent of manure -f- 1.8 per cent of 



iron sulphate 



3 per cent of manure -\- 3 per cent of 



calcium sulphate 



Whole soil 



Percent. 

 682 



643 

 439 

 578 

 737 

 375 

 244 



Percent. 



52 



Percent. 

 12. 7 

 12.3 



12. 6 



13-7 



11. 8 



12. 7 



10. O 



4-7 



Percent. 

 27. I 

 27. 2 



27. o 



25-5 

 27.8 

 27.9 



26. o 



17-3 



Percent. 



1-3 

 1.6 



2.7 



2.8 



2.9 



3-6 



6.2 



3-5 



Percent. 

 1.4 

 I. 2 



1.9 



1-5 

 1-3 



2-5 



3-0 

 0.6 



Percent. 



O. 24 



•31 



.19 



.64 



•50 



.48 



.62 



Table IX shows the results of the partial analysis of the whole soil and 

 of the colloid suspensions. Two evaporations were made in the sihca 

 determinations, but the silica residue was not purified with hydrofluoric 

 acid. In this connection it may be stated that the fused cake, when 

 taken up with water, never contained any visible undissolved residue. 



The composition of the colloid suspensions from the differently treated 

 soils does not vary enough to indicate any fundamental differences due 

 to the soil treatments, except when gypsum was added. All other 



