4 
ON CHEMISTRY. 
tity of water of absorption which it can retain. In fact, if soil so 
dried by actual fire heat, be long exposed to the air, it will absorb a 
corresponding degree of moisture ag^in, though it remain dry to ap¬ 
pearance. Davy, Mr. Johnson, and other writers, consider the ab¬ 
sorbent powder of soils to be indicative of their composition if not of 
their comparative fertility. 50 parts out of 400, may be lost out of 
some soils—others lose but 20 or even 10 parts; and in these, 
sand is very predominant. I doubt the criterion much : having an 
example before me of a very fine loam which I find to be almost, 
altogether fine silex, and which loses 5i per cent by a heat of about 
300 deg. Coarse sand indeed is very little retentive, but siliceous 
earth is comparatively, very highly so. 
2. Process of Washing .—Suppose that 20 parts of water have been 
separated from 400, by the heat of 300 degs—380 parts or grains, 
remain : let these be boiled in four ounces of rain water, and then, 
suffer the particles of soil to subside. When cold, decant the clear 
liquid; then add a little more water to the deposited matters,—stir 
them together, and pour the whole into a paper filter, which has been 
previously dried and weighed. Wash in all the dregs, and catch 
the drainings. If the liquid decanted off, be not quite bright, let it 
pass through the matters in the filter: finally, wash those, by adding 
a little more pure water. These waters of lixiviation contain all the 
salts, and other substances soluble in water; and they should be re¬ 
tained in a vessel for future experiment. The filter and its contents 
are tp be dried,—first by absorption on a lump of chalk ; then, by 
gradual exposure to a strong heat: to that at least, which the side of 
a parlour stove furnishes. The paper and its contents are then to be 
weighed; and the quantities of soil remaining, will be ascertained 
by substracting the weight of the paper. Should the soil retain any 
degree of moisture, it must be dried in a saucer, or upon a broad 
plate of tin, and be then rebalanced. 
3. Process by Muriatic Acid .—It will facilitate the description to 
place before the reader an imaginary analysis, which, however, will 
contain a close approximation to a real process. We will, therefore, 
presume that by drying and lixivitation, the original quantity of 400 
grains has been reduced to 360 grains. These might be treated 
in bulk with the acid; but I propose to the analyst, to divide the 
soil into two equal parcels, each of 180 grains; because, as the ob¬ 
ject is to detect the carbonate of lime, it may, with advantage, be ef¬ 
fected by a comparative experiment, which will prove very instruc¬ 
tive. 
Muriatic Acid dissolves carbonate of lime, (chalk,) Magnesia, 
