66 Journal of Agricultural Research voi.xv. no. a 



Clay separation water. — For a purpose stated later, a mechanical 

 separation of the clay from these soils was made in the following manner : 

 Six hundred gm. of the air-dry fine soil was shaken with about 2 liters 

 of distilled water in a rotary shaker for eight hours. After the suspen- 

 sions thus obtained had settled overnight, the clayey liquor was carefully 

 siphoned off. The soil residues were then thoroughly agitated with a 

 fresh portion (1,5 to 2 liters) of distilled water, then allowed to stand until 

 the particles of more than 0.005 mm. in diameter had settled out, when 

 the new clay suspension was siphoned off. This washing process was re- 

 peated for 10 days. Even then not all the clay had been removed from 

 the coarser soil members. The volumes of the combined washings were, 

 for plot I soil, 16,710 cc; for plot 4, 18,530 cc. 



To remove the clays from these suspensions they were allowed to stand 

 for two days, by the end of which five-sixths of the clay had settled out. 

 The overlying liquors were carefully drawn off, and the clay still remaining 

 in suspension in the liquor was almost completely removed by flocculation. 

 The flocculating material first used was ammonium chlorid. This was 

 added in 5-gm. portions previously dissolved in a little distilled water, 

 and thoroughly stirred through the liquor. 



In the case of the suspension from plot i soil, flocculation began shortly 

 after the addition of two portions, or 10 gm., of the flocculant; but three 

 portions, or 15 gm., caused no appearance of flocculation in the suspension 

 from plot-4 soil. This liquid had the appearance which slight alkalinity 

 gives to clay suspensions, although rather sensitive pink litmus gave no 

 alkaline reaction when moistened with it. The addition was tried, there- 

 fore, of concentrated hydrochloric acid, drop by drop, with stirring after 

 each drop had been added. Upon the introduction of the tenth drop, 

 flocculation began rather sharply, so that the addition of the acid was 

 discontinued. 



The liquors drained off from these flocculated clays were still faintly 

 cloudy, and separated a little clay on long standing. 



Of the washings from plot i, 14,530 cc, and of those from plot 4, 13,030 

 cc, were withdrawn, filtered, evaporated to dryness, and the evaporation 

 residue ignited to get rid of organic matters and ammonium salt. The 

 ignited residues were moistened with acid, taken up with hot water, 

 filtered, and subjected to analysis for potash by the method already 

 described. 



The quantities of potash found in the total wash waters were : 



Percentage of soil. 



Plot I, untreated o. 0038 



Plot 4, dressed with potash 0087 



In view of the differences in method of treatment, in proportion of 

 soil to water, and in duration of the exposure of soil to solvent, it is 

 remarkable that the quantities of potash removed by water were in all 

 cases so nearly the same for the respective soil samples. 



