34© TlMEHRl. 
that 907 per cent, of the phosphoric acid present had 
been absorbed and fixed by the soil. 
Experiment II. — was a repetition of the previous one, 
except that only 250 parts of the air-dried soil were taken 
with 1000 parts of the superphosphate solution. After 
five days the filtered liquid contained '38 parts of phos- 
phoric acid per 1000, which, corredted for the water 
already present, showed that 61 '3 per cent, had been re- 
tained by that quantity of soil. 
The proportion of phosphoric acid used in the above 
experiments, namely, 2 and 4 parts respectively to 1000 
of soil, is, of course, far greater than would be used as 
manure, seeing that it would be about equal to the addi- 
tion of 2 tons and 4 tons of the acid, or its equivalent in 
superphosphate, to an acre of soil 6 inches deep ; whilst, 
in actual practice, 1 or 2 hundredweights would at the 
most be employed. 
Notwithstanding the excessive proportion used, the 
results of the experiments prove, as was anticipated, that 
on bringing superphosphate into contact with certain 
soils, the greater part of the phosphoric acid present 
does enter into union with some constituent of the soil to 
form an insoluble compound ; and this in spite of the 
presence of abundance of water strongly acidified with 
acetic acid. The full significance of this latter fact will 
be evident when it is understood that compounds of phos- 
phoric acid that are insoluble in dilute acetic acid are con- 
sidered to have no manurial value, as they likewise resist 
the action of the much weaker natural solvents in soil 
and thus prove incapable of supplying the phosphorus 
that plants require. For this reason, minerals consisting 
chiefly of phosphate of alumina and iron (which can be 
