BULLETIN OF THE BUSSEY INSTITUTION. 201 
the carbonate of lime. Indeed, F. Schulze* has attributed to this cause 
the presence of dissolved carbonate of lime in loam waters such as 
were the subject of my experiments. He says, ‘‘ The soluble humus-like 
constituents of the soil seem to increase the solubility of carbonate of 
lime, since the first aqueous extract obtained after the soil has been left 
in contact with water for a sufficient length of time contains in solution a 
larger quantity of carbonate of lime than corresponds with the solubility 
of this substance in pure water.’? The idea was first suggested, I 
believe, by Verdeil & Risler,t who dwelt upon the fact that loams contain 
a neutral, soluble, organic matter analogous to sugar ¢ which facilitates the 
solution of a variety of inorganic matters. It is not easy to prove how 
much solvent action may be exerted by the organic matters of loams in 
respect to carbonate of lime, or whether, indeed, they have any solvent 
action at all for this substance. For my own part, I attach little or no 
importance to the idea in the present connection. It is plain, at all events, 
that no such solvent action could possibly have occurred in the cases of 
the calcined loams and ashes, to be described directly, since these sub- 
stances were wholly free from organic matters. It is to be remembered 
withal, that there are several facts which go to show that the presence of 
lime salts in a soil may decidedly hinder the solution of organic matters, 
which become soluble when the lime salt is removed. Thus, as Knop § 
and Hoffmann have shown, when a loam is percolated with water, the first 
portions of the filtrate are commonly colorless; but after a while the suc- 
ceeding portions of the filtrate are seen to be colored, — at first yellowish, 
and sometimes even brown. But the appearance of the coloration is 
coincident, as Knop urges, with the removal of a quantity of Jime salts 
that were originally contained in the earth. 
It may be said of my own experiments, that the first portions of the 
percolates from loams were always less deeply colored than the succeeding 
portions. To test the influence of an excess of lime, a quantity of dry 
earth from the Plain-field was mixed with whiting; enough carbonic- 
acid water to moisten the earth was added; the mixture was left to soak 
for some days in a closed flask, then transferred to a percolator, and the 
color of the liquor that drained from it was observed. The first 50 ce. 
fraction of percolate, though not colorless, seemed to be less deeply col- 
ored than usual; but the color of the subsequent fractions was similar to 
that of the percolates obtained from the earth alone, and on continuing 
the percolation with pure water, and with carbonic-acid water, the usual 
colorations were obtained. 
Special trials were made, furthermore, in the case of the earth from the 
Plain-field, in order to determine whether the percolate therefrom con- 
* In his ‘‘ Lehrbuch der Chemie fiir Landwirthe,” Leipzig, 1866, 1. 676. 
+ “ Journal fiir praktische Chemie,” 1852, 57. pp. 115, 117. 
t Compare De Saussure, “ Récherches sur la Végétation,” p. 174. 
§ In his “ Lehrbuch der Agricultur Chemie,” Leipzig, 1868, 1. pp. 304, 458, 
516. 
