268 
solved as ammonia muriate, and its quantity may be 
ascertained by precipitating it either with soda or 
phosphate of soda. In the former case, the sub- 
stance obtained when washed on a filter, dried and 
ignited, is pure magnesia; in the latter, it is the 
ammonia-phosphate of magnesia, and when dried at 
the moderate heat of 120° Fahr., it represents by its 
weight about six times of the magnesia present; or 
for 100 parts, 163 of magnesia. 
‘*« When acomplete analysis of a soil is to be made, 
the following apparatus is convenient:—A large glass 
flask, or matrass, with a sucked-in or concave thin 
bottom. This should hold at least a quart of water; 
and when the soil and dilute acid are introduced, it 
is to be placed on a stand over the gentle flame of a 
spirit lamp, while the beak of a large glass funnel, 
having its mouth covered with a porcelain basin, 
filled with cold water, is inserted into the neck of a 
flask. By this arrangement, a continual ebullition 
may be maintained in the mixture of soil and acid, 
without loss of acid, or nuisance from its fumes, be- 
cause the vapours are condensed whenever they reach 
the cold basin above the funnel, and a perpetual co- 
hobation takes place. A boiling heat may be kept 
up in this way till every constituent of the soil, ex- 
cept the silica, becomes dissolved. Muriatic acid is 
generally preferred for the analysis of soils, and in 
somewhat greater quantity than the bases in the 
given weight of soil can neutralise. The funnel and 
porcelain basin should be properly supported upon 
the rings of the chemical stand. I generally subject 
100 grains of soil to the action of boiling dilute acid 
in this way for 6 or 8 hours; at the end of that 
period, I throw the contents of the matrass upon 
a filter, and super-saturate the filtered liquid with 
ammonia, The silica which remains on the filter 
having been washed in the process, is dried, ignited, 
and weighed. The alumina, iron-oxide, and phos- 
phate of lime, thrown down by the ammonia, being 
washed in the filter, and dried to a cheesy consist- 
ence, are removed with a bone or tortoise-shell 
blade into a silver basin, and digested with heat in 
a solution of pure potash, whereby the alumina is 
dissolved, when its alkaline solution is to be passed 
through a filter, then saturated with muriatic acid, 
and next super-saturated with ammonia. Pure white 
alumina falls, which is to be separated on a filter, 
washed, dried, ignited, and weighed. ‘The iron and 
phosphate of lime on the alkaline filter may be dried, 
gently ignited, and weighed, or otherwise directly 
separated from each other without that step, by the 
action of dilute alcohol, acidulated with sulphuric 
acid, at a gentle heat» ‘Thus the iron-oxide will be 
dissolved, and its solution may be passed through a 
filter, while the sulphate of lime will remain upon 
it, to be dried, ignited, and weighed. Five parts of 
it correspond to four of phosphate. The iron is 
obtained by precipitation with water of ammonia, fil- 
tration, and ignition. The first filtered liquor, with 
excess of ammonia, contains the lime of the carbon- 
ate, and the magnesia. ‘The former is separated by 
a solution of oxalate of ammonia, with digestion in a 
gentle warmth for a few hours, filtration, and very 
gentle ignition of the washed dry powder, when the 
pure carbonate of lime is obtained. ‘The magnesia, 
existing in the filtered liquor as an ammonia-muriate, 
may be obtained by precipitation with soda, or phos- 
phate of soda, as already described. For some 
refractory soils, in which the alumina exists as a 
double or triple silicate, it becomes necessary to 
fuse 50 grains of the sample, in fine powder, mixed 
with four times its weight of dry carbonate of soda, 
the mixture being put into a platinum crucible, 
and into a cavity in its centre, 50 grains of hy- 
drate of potash being laid. ‘The crucible being 
slowly raised to a red-white heat, affords a fused 
liquid quite homogeneous, of a grey or brown 
SOIL. 
colour, according to the metals present in it. Man- 
ganese gives a purple tint; and iron a reddish brown. 
The fused matter should be poured out into a shal- 
low platinum basin ; and, whenever it cools, it should 
be pulverized, dissolved in dilute muriatie acid, the 
solution evaporated to dryness, the dry mass again 
digested in hot water, acidulated with muriatic acid, 
and the whole thrown upon a filter. Pure silica 
will remain on the filter, to be washed, dried, ignited, 
and weighed. ‘The filtered liquor contains the re- 
maining constituents of the soil, and is to be treated 
as already described. : 
‘‘ Besides these systematic investigations, re- 
searches may be made for certain peculiar substances, 
and especially the neutro-saline constituents. In 
this view 100 grains of the soil may be triturated 
with 20 times their weight of distilled water, placed 
in a beaker, till the clayey matter subsides, and the 
clear portion then be decanted into a filter. A little 
of the filtered liquor should be tested with nitrate of 
barytes, and also with oxalate of ammonia; and if 
each portion yields a precipitate, they show the pre- 
sence of sulphate of lime; and the following steps 
ought to be taken to eliminate it entirely: 200 grains 
of the soil should be triturated with a quart of dis- 
tilled water, holding 50 grains of sal-ammoniac, in 
solution. The mixture should be allowed to clarify 
itself by subsidence, when the supernatant clear liquor 
should be filtered, and evaporated down to 2 ounce 
measures, and then mixed with that bulk of strong 
whisky (11 per cent. overproof). The whole sul- 
phate of lime will be now separated from the fluid, 
and after being drained on a filter, may be dried, 
ignited, and weighed. For determining the alkaline 
salts, the water filtered from the 100 grains of the 
soil should be evaporated down to one-fifth of its 
bulk, and then treated—lIst, with nitrate of barytes 
for the sulphates ; 2d, with nitrate of silver for the 
muriates; 3d, with oxalate of ammonia, for the ni- 
trate or muriate of lime (provided no sulphate of 
lime is indicated by the first test) ; 4th, with 
litmus paper, for alkaline or acid reaction; 5th, 
with soda-chloride of platinum for potash salts, 
which are very valuable for the vigorous growth 
of many plants. The portion of soil tested for 
potash salts should, before being digested in water, 
be gently calcined, to insure the expulsion of every 
particle of ammoniacal salt, otherwise the precipi- 
tate afforded by soda-chloride of platinum would be 
fallacious. 
‘* Another peculiar research of great importance 
is that which determines the amount of ammonia in 
a soil; and which may exist either ready formed, or 
in its elements, capable of affording a portion of the 
azotic food so indispensable to vigorous vegetation. 
The actual ammonia is easily obtained by distilling 
the soil along with some milk of lime. The distilled 
water will contain all the volatile alkali, which may 
be measured by the number of drops of a standard 
dilute acid, which it will saturate. The potential 
ammonia, slumbering, so to speak, in its embryo 
elements, may be estimated by igniting 200 grains of 
the soil with its own weight of a mixture of hydrate 
of soda and quicklime. ; f 
‘¢ Since the phosphates are such precious ingre- 
dients towards fertilizing soils, it is desirable to pos- 
sess a clear and simple test of their presence. For 
this purpose, digest the soil, for an hour or so, with 
a moderate heat, in dilute nitric acid, free from mu- 
riatic (viz. which affords, when largely diluted, no 
precipitate, by the addition of a solution of nitrate 
of silver). Throw the mixture on a filter, and 
to the filtered liquid add potash-water, cautiously, 
till the instant that a precipitate begins to appear; 
then drop into it a weak solution of nitrate of silver. 
If any phosphoric salts be present, a yellowish pre- 
cipitate will immediately fall, which is re-soluble in 
ee eeese rea 
