462 :StH(lks of a Scot(if</i JJrij'l Soil 



In considoiinor the figures in Tables III and IV it is to be remembered 

 that the method of mechanical analysis adopted^nvolves the treatment of 

 the soil with dilute hydrochloric acid before fractionation is performed, 

 and that therefore ail com))ounds easily soluble in acid were removed 

 and are not shown in the analyses. Table II shows that appreciable 

 quantities of phosphoric acid, potash, lime, and magnesia were 

 dissolved from the oi'iginal soil by dilute citric acid. No doubt 

 cjuantities of all these as well as of iron and alumina were dissolved 

 by the dilute hydrochloric acid used before the mechanical separation 

 into fractions was commenced. In the case of phosphoric acid much 

 the greater part of this constituent present in the soil is easily soluble 

 in dilute hydrochloric acid, for whereas Table II shows that the soil 

 contained (t-3() per cent, of phosphoric acid soluble by digestion in 

 strong hvdrochloric acid, Table IV shows that only 0-12 per cent, was 

 found in the whole of the mechanical fractions. 



Table III shows that, as has been found by all previous investi- 

 gators of this subject, the percentage of iron and alumina increases 

 and the percentage of silica deci'eases with a decrease in the size of the 

 particles. In the case of other elements the results of different 

 investigators do not agree so well, but the majority of workers found 

 an increase of potash, soda, lime, magnesia, and phosphoric acid in the 

 smaller particles. The evidence with regard to some of these is, 

 however, very conflicting. 



Puchner' working on three ditt'erent soils a heavy loam, a silty 

 soil (locssial) and a coarse sandy soil from gneiss — found the content 

 of lime, magnesia, and phosphoric acid to be irregular, and that of 

 silicic acid, soda, and potash to be smaller in the finer fractions. 



Schneider''^, for a residual soil from the disintegration of augite- 

 andesite, found that the percentage of lime decreased with the size of 

 the particles, while Loughridge' found the lime irregular, and Clerk. 

 Gortner and VaiH found the highest percentage of this constituent in 

 the silts, and the lowest in the clays. 



Schneider^ found the percentages of magnesia anil phosphoric acid 

 irregular. 



In Craibstone soil the percentage of phosphoric acid in the fractions 

 increases regularlv as the size of the particles becomes less. This is 

 in agreement with the results of most workers. It indicates that there 



> Landw. Vers.-Stat. 1907, 66. 463 = Amcr Jour. Sci. 1888, 36. 2:56. 



' Amer. Jour. Sci. 1874, 7, 17. « Amer. Chan. Jour. lOOS, 39, U)3. 



' loc. cit. 



