tent in the decay of vegetable matters and is also absorbed from
the air, ulmic and humic acids are made soluble, and combine with the
ammonia as well as with lime, oxide of iron, etc. In some cases the
ulmates and humates thus produced may be extracted from the peat by
water, and consequently occur dissolved in the water of the swamp from
which the peat is taken, giving it a yellow or brown color.

_Ulmates_ and _Humates_.--Of considerable interest to us here, are the
properties of the compounds of these acids, that may be formed in peat
when it is used as an ingredient of composts. The ulmates and humates of
the alkalies, viz.: _potash_, _soda_, and _ammonia_, dissolve readily in
water. They are formed when the alkalies or their carbonates act on
ulmin and humin, or upon ulmates or humates of lime, iron, etc. Their
dilute solutions are yellow, or brown.

The ulmates and humates of _lime_, _magnesia_, oxide of _iron_, oxide of
_manganese_ and _alumina_, are insoluble, or nearly so in water.

In ordinary soils, the earths and oxides just named, predominate over
the alkalies, and although they may contain considerable ulmic and humic
acids, water is able to extract but very minute quantities of the
latter, on account of the insolubility of the compounds they have
formed.

On the other hand, peat, highly manured garden soil, leaf-mold, rotted
manure and composts, yield yellow or brown extracts with water, from the
fact that alkalies are here present to form soluble compounds.

An important fact established by Mulder is, that when solutions of
alkali-carbonates are put in contact with the insoluble ulmates and
humates, the latter are decomposed; soluble alkali-ulmates and humates
being formed, and _in these, a portion of the otherwise insoluble
ulmates and humates dissolve_, so that thus, in a compost, lime,
magnesia, oxide of iron, and even alumina may exist in soluble
combinations, by the agency of these acids.

_Crenates_ and _Apocrenates_.--The ulmic and humic acids when separated
from their compounds, are nearly insoluble, and, so far as we know,
comparatively inert bodies; by further change, (uniting with oxygen)
they pass into or yield the crenic and apocrenic acids which, according
to Mulder, have an acid taste, being freely soluble in water, and in all
respects, decided acids. The compounds of both these acids with the
alkalies are soluble. The crenates of lime, magnesia, and protoxide of
iron are soluble, c