ON THE DISCRIMINATION OF SOILS. 
189 
its weight of the diluted sulphuric acid added. The whole must then be boiled in 
a glass vessel for one hour. This boiling can frequently be effected in a short phial 
of thin glass, or a Florence flask, placed upon the cheek of a common fire-grate, 
first at a distance from the fire. A small piece of paper should be put under the 
phial : and, as the liquor becomes hot, the vessel may be safely made to approach 
the fire till the heat is found suflficient to create ebullition. When that is per- 
ceived, the boiling should be maintained for one complete hour. 
The sulphuric acid will take up iron from the soil, and also the alumen, or pure 
clay, which it may contain. The iron would be abstracted without heat ; but the 
act of boiling is required to efifect the solution of the alumen. 
When the liquid has become cold, the contents of the phial are to be poured 
upon a paper filter, previously weighed ; and every grain remaining in the vessel 
must be carefully washed out by repeated rinsings with pure water, all the washings 
being poured into the filter. More water is then to be added till the drainings 
come away free from acid taste, after which, the filter and its contents are to be 
dried, first by absorption on a piece of chalk ; and, finally, on the grate or other hot 
surface, till they become completely dry. Being then weighed, and the weight of 
the paper subtracted, the net product will give the amount of iron and alumen. 
A good loam will lose, perhaps, ten grains out of the 110, which we will 
suppose to have been the weight of the soil submitted to the test of sulphuric acid ; 
and of these four will be iron, and the remaining six alumen, or pure clay. The 
substance upon the filter may weigh from 94 to 100 grains, or nearly so ; it will 
consist chiefly of siliceous or flinty earth. 
The proportions adduced approximate to the results of actual experiments ; and 
we know that the loam so tested was most admirable. Some latitude must be per- 
mitted, and soils may contain some few grains, more or less, of iron, chalk, and 
clay. But as a general rule in analysis it may be stated, first, that in 120 grains 
of a rich light loam, from 90 to 100 ought to consist of flinty insoluble earth j 
second, that the soluble portion ought to contain from six to ten grains of clay, and 
perhaps nearly as much chalk and iron. The latter ingredient varies much in soils 
of difl^erent colour. Those of the greyish brown, or umber tint, appear to be the 
best, the iron being in that peculiar state of chemical oxidation which is most pro- 
pitious to the health of plants. If a loam be very deficient in chalk, or the matter 
of pure clay, — as the well conducted experiments of analysis will demonstrate, — 
the chemical horticulturist can amend it. Caution and precision, both of which will 
be attained by practice, will be of course required ; but if a soil be found so deficient 
in clay that 120 grains contain but two grains, discoverable by the test of sulphuric 
acid, it will be very easy to add three, four, or five grains of clay, dried and reduced 
, to fine powder ; or, of pipe clay, two, three, or four grains ; the same may be said 
; of chalk. If, on the contrary, a soil be found to consist chiefly of coarse gravelly 
sand, it will not be difficult to separate a portion of that predominant quality by 
! washing oflf some of the soil, and adding those fine separable matters to the bulk. 
Thus one-third of a barrow of harsh soil should be washed in two or three waters ; 
j the matters that float, or rather that are not deposited within the period of a second 
or two of time in water, being poured over the remaining two-thirds, and the whole 
Intermixed as the water of lixiviation dries oflT. Thus the heavy sharp sand 
