46 
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tions, but the presence of sulphureted hydrogea in the soil will gene- 
rally indicate when fermentation is in progress in the soil. 
The composition of peat or mold varies with the nature of the plants 
which produce it. Plants containing tannin give an acid mold, while 
those which have no tannin form a mild mold more favorable to culti- 
vation. The organic principles which are found in mold are ulmic acid, 
free or combined, in the latter case forming soluble ulmates, which are 
absorbed by plants during vegetation, and a black substance soluble in 
water, and called extract of mold, to which humus owes its color. 
Although extract of mold is soluble in water, it should not be con- 
founded with ulmic acid. It acts, during vegetation, by aiding in rap- 
idly heating the soil which contains it, by absorbing moisture, by 
appropriating the elements of the atmosphere and of manures to form 
ammoniacal compounds, the nitrogen of which is easily assimilated by 
plants; and finally by giving rise to carbonic acid, which is dissolved 
by water. 
In this condition, carbonic acid favors the, earliest development of 
plants before the growth of the leaves; it dissolves the otherwise insol- 
uble phosphates, it converts the insoluble earthy carbonates into solu- 
ble bicarbonates, thus enabling them to furnish to plants the lime and 
magnesia which they need. 
ULMIC COMPOUNDS, OR PEATY MATTER.—Braconnet was the first to 
observe that in treating wood with potash a black acid, comparable to 
humus, was formed which he called ulmicacid. M. Chevreul also found 
that under the influence of the alkali the oxygen of the air is rapidly 
absorbed. Certain trees, and especially elms, exude a brown liquid 
which, according to the observations of Vauquelin and Klaproth, is an 
ulmate of potash and ammonia. The action of potash upon wood has 
been examined by M. Péligot. It results from the observations of this 
chemist that when a mixture of sawdust and potash is heated to about 
300°, water, hydrogen, oily products, and wood-spirit are disengaged, 
besides which, carbonate, oxalate, formiate, and ulmate of potash are 
formed. Ulmic acid thus obtained will be yellow if the temperature at 
which the reaction takes place is not too high; but when the mixture is 
heated without precaution the acid is black. The final result of the de- 
composition of woody material by potash is carbon, and if the tempera- 
ture were sufficiently high, hydrate of potash, acting as an oxidizing 
agent, might even cause the combustion of the carbon, in which case 
hydrogen would be disengaged. The yellow acid has been called lign- 
humic acid; the black acid, called lignulmic acid, forms with bases salts 
which have the general formula MO, C** H?8 O8, 
Lignulmic acid is brown, almost black; it is insoluble in water, but 
dissolves in concentrated sulphuric acid. It.is soluble in alcohol; with 
alkalies it forms salts of a deep-brown color, which are uncrystallizable. 
The other lignulmates are insoluble, and may be obtained by double 
decomposition. M. Malogati obtained a black erystallized acid by heat- 
ing on the water-bath for several hours a solution of sugar containing _ 
a small quantity of nitric acid. 
M. Mulder has published a work on these black acids, of the principal 
results of which the following is a summary: 
When a solution of 22 parts of sugar and 1 of sulphuric acid in 40 
parts of water is heated to about 80°, a brown deposit is soon formed, 
which M. Mulder considers an ulmate of ulmine. This substance, treated 
with potash, yields ulmate of potash and leaves a deposit of ulmine, the 
composition of which is C* H'® O4, Ulmate of potash treated with 
