24 
ACTION OF LIME AS A MANURE. 
which latter originated from the hydrate in the current of carbon 
dioxide. Such a process will, of course, also take place in soils 
between the basic phosphates of iron and freshly applied lime 
which will display its action there also in both forms, as hydrate 
and bicarbonate; as a result the crops will be benefited as to 
their nutrition with phosphoric acid.—Similar processes are 
certainly accomplished still more easily between calcium com¬ 
pounds and ferrous phosphate ; the latter, though easily assimi¬ 
lable as such, is liable to be occasionally oxidized to the less 
assimilable ferric phosphate, but would be prevented from this 
change, if its acid combined with lime. 15 
Contrary to its beneficial action on the phosphates in the 
paddy soil, lime did not affect them to any appreciable extent 
in the irrigated subsoil from the dry field. As the two soils 
are of the same geological origin, having, as to their mineral 
matter, a very similar composition, and differing only in the 
content of humus which is abundant in the paddy soil but 
almost entirely absent from the yellow subsoil, there can be no 
doubt that in our case the humus pla}-ed an important part in 
bringing about the action of lime on phosphates. The mineral 
part of the soil used consists of a large proportion of hydrated 
silicates with which the lime combines unless it is absorbed by 
substances which have a stronger affinity to it. The humus 
and the carbon dioxide generating in the paddy soil probably 
united at once with the lime when it entered the soil, and 
thus preserved it in a state in which it could still act on the 
soluble phosphate, while in the subsoil destitute of humus 
nothing interfered with the union of the lime with the hydrated 
silicates. We do not, however, believe that in all soils poor in 
15 Upon boiling basic ferric phosphate, containing 0.1 grms. of phosphoric- 
acid and 0.225 grms. of ferric oxide, with lime water in absence of carbon 
dioxide, rapidly filtering and treating the content of the filter with a hot 5 
percentage solution of acetic acid, 64.1 °/ 0 of the phosphoric acid applied 
passed into the filtrate. The same quantity of basic ferric phosphate when 
digested in the cold for 72 hours with lime water, collected on a filter and 
extracted with hot 5 percentage acetic acid, yielded 42.2 °/j of the phosphoric 
acid applied, to the extract. 
