ABSORPTION EXPERIMENTS. 17 



show the problems in agricultural chemistry that were exercising the 

 mind of this contemporary of Liebig more than a half a century ago, 

 and which have been to a large extent overlooked and disregarded in 

 more modern work. On page 316, Way says: 



It is to be observed that the property of sand to arrest and separate saline sub- 

 stances from solution is very limited in extent and requires careful arrangements to 

 make it evident at all by experiment. It differs also fundamentally from the chem- 

 ical power, which it is the object of the present paper to explain, inasmuch as the 

 physical action of capillarity is exerted on the whole salt, whilst that we are about 

 to describe has relation only to the alkaline or earthy base. Furthermore, the former 

 property is only the resultant of two opposite forces, that of the surface attraction of 

 the sand and of water for the salt. It can only, therefore, operate a condensation of 

 the salt in relation to the strength of the solution, the salt being continually shared 

 in given proportions between the sand and the water, so that eventually the' whole 

 is washed away. Such, however, is not the case with the compounds which are 

 formed in the soil with solutions of different alkaline bases, for, so far as the experi- 

 ments have gone, they appear to be wholly insoluble in pure water. 



Again, on page 359 et seq., where the author- cited is discussing a 

 simple experiment in which 2,000 grains of white pipe clay had been 

 boiled with 4,000 grains of -a 1 per cent solution of potassium Irydroxid, 

 the mixture filtered and the filtrate analyzed, we read: 



When simply digested with the solution of potash in the cold the clay absorbed 

 1.050 per cent of potash. When the materials are boiled together the absorption is 

 somewhat greater or 1.1716 per cent. This, however, is not a material difference. 

 In analytical chemistry it is usual to employ caustic potash as a means of separating 

 silica from other substances with which it may be mixed. When boiled with potash 

 the silica is dissolved and forms a soluble silicate of the alkali. In the experiment 

 which has just been described we find clay, which is usually thought to contain 

 silica in a free state, not only refusing to give up that silica to potash, but actually 

 combining with and removing from solution the alkali. It should be understood, 

 however, that this result is affected by the relative proportions of the two substances, 

 since a stronger solution of potash will, even in the case of clay, dissolve out silica. 



The experiment is of interest, however, in showing how powerful is the tendency 

 of soils to form new compounds where the opportunity of gratifying that tendency 

 may be offered them. 



These observations are in essential agreement with the results of 

 investigations which are at present being carried on in this laboratory. 

 The tabulated and systematic presentation of the figures obtained will 

 be reserved until more complete data have been collected, but it seems 

 desirable, briefly, to outline here the method being followed and some 

 of the conclusions that have already been reached. Weighed portions, 

 usually 10-gram lots, of clays and rock powders are digested with 

 50 cc of tenth-normal solutions of various electrolytes. After com- 

 plete subsidence or clear filtration the filtrates are analyzed. 



