



325 
slowly upon the surface of the soil. The above solution contained 
2.01 grams of P, O,. After 3000cc. of water had been drained 
through phosphoric acid was present in the washings and continued 
during the experiment, when nearly 30000cc. more of spring water 
had passed through the soil. 
An analysis of the soil was then made. A sample from the sur- 
face gave .0073 per cent. of P, O, ; one from the center .00342 per 
cent., and from the bottom of the Jar .00198 per cent. 
Haperiment No. 5. 
‘'wo small fiber flasks were filled with dry garden soil, being the 
same as that used inexperiment No. 4. 
Five grams of carbonate of lime was mixed with the soil of one 
and then to each was slowly added 250ce. of distilled water contain- 
ing .2 grams P, O,. 
The first drainage to come through gave phosphoric acid, and a 
much heavier precipitate was obtained from the one having carbon- 
ate of lime. * 
After a short time, however, the amount of phosphoric acid in the 
drainage coming from the soil containing carbonate of lime began to 
diminish while the other showed a marked increase. 
On further washing with distilled water, the phosphoric acid 
nearly disappeared from the drainage coming from the earth con- 
taining carbonate of lime, while in the other its presence was very 
marked. 
The last experiment would seem to indicate that while the ulti- 
mate tendency of carbonate of lime in a soil is to fix and retain any 
phosphoric acid applied to the soil, its first effect from the liberating 
of carbonic acid is to aid in washing away a portion of it, providing 
there be present sufficient percolating or moving water. 
Fixation of Phosphoric Acid by a Soil trom a Solution. 
These experiments were made as preliminary to future investiga- 
tions. ‘To understand the results tabulated in the following tables 
a few explanatory notes may aid. 
The soil used was a garden soil, the same as used in previous ex- 
periments, and was quite dry. Flasks were used to hold the sub- 
stances. ‘I'he contents were thoroughly shaken together, the flasks 
loosely corked to prevent the admission of any foreign matter and 
kept at temperature of laboratory, obscured from hight. 
In the last case, instead of adding the phosphate direct, a solution 
was made by shaking water and phosphate together, then filtering 
and adding enough of the solution to contain 1.608 grams of P, O,. 
In the others, where phosphate was used, but 68 per cent. of the 
P, O, (as given in column showing P, O, added), was in a soluble 
form. 
