SALT. 125 
induces this electric action, this decomposition 
of the elements of soil. Germination produces 
carbonic acid, by decomposing water. ‘The very 
-first act of life in a seed is to evolve carbonic 
acid, by its carbon combining with oxygen of 
air, and its second act is to decompose water. 
Its oxygen combines with the carbon of the seed ; 
a single bean produces many times its bulk of 
carbonic acid gas; and in the soil would sur- 
round itself with an atmosphere of carbonic 
acid. This evolved, begins its action upon the 
silicates. The living seed begins the electric 
action, and the plants exert and keep up this 
influence. Salts act in a similar way; but above 
all, over all, influencing all, is the living plant. 
This electric action induced, extends to unde- 
termined distances ; hence there is a transfer, as 
is usual in all cases of galvanic decomposition, of 
substances remote from the plant, to its root, 
where they are taken up. It is not the potash 
and lime, &c., immediately in contact with the 
root, which alone supplies the plant; but under 
the galvanic influence, an undetermined portion 
of soil is decomposed. This decomposing agency 
of plants wholly destroys all confidence in expe- 
riments, undertaken to prove that pure water 
alone can nourish plants. The containing ves- 
sel, that is the vessel in which the experiment is 
made, is itself always decomposed. If to guard 
against an error glass is used, it has already been 
shown that this is only a combination of silicates, 
and these will be transferred from the glass to 
the plant.” 
SALT (Common),—chemically Chloride of So- 
dium. A compound of one equivalent of chlo- 
rine and two equivalents of sodium. It may be 
directly formed by burning sodium in chlorine, 
or by heating it in hydrochloric acid gas; and it 
is deposited in crystals from a solution of muri- 
ate of soda. But it naturally occurs in vast 
quantities as a mineral deposit of the saliferous 
sandstone formation,—in immense quantities as a 
saline impregnation of sea-water and of the water 
of salt springs,—and in small quantities as a sa- 
pid ingredient of most of the waters which flow 
from any part of the land into the sea. It may 
be regarded as a true mineral; for it is always 
the solid or ultimate form into which the muri- 
ate of soda of the sea and of salt springs is re- 
solved by evaporation; and it passes from the 
interior of all countries toward the final recep- 
tacle of rivers; and it generally accumulates 
more, and forms a stronger brine, in inland seas 
which have no outlet, and particularly in such 
a& narrow evaporating basin as the Dead Sea, 
than in the open and far-expanding ocean. Its 
crystals, from slow evaporation, are cubic,—and 
from rapid evaporation, are hollow, four-sided 
prisms; and they contain no water of crystalliza- 
tion, but enclose particles of water among their 
interstices, and decrepitate powerfully when 
heated. Its taste is agreeably saline. It slightly 
deliquesces in a moist atmosphere, but under- 
Lees cee 
goes no change in adry one. It fuses at a red 
heat, and cools down into a brittle transparent 
mass. It dissolves in about 23 times its weight of 
water, of any temperature from 60° to 212°; and 
it passes into muriate of soda in the act of dis- 
solving. Solid common salt is thus akin in con- 
stitution to an oxide, and consists of two simple 
or elementary ingredients,—a metal and a salt 
radical; and dissolved common salt is strictly a 
true salt, and consists of two compound or binary 
ingredients,—an oxide and an acid. 
The Varieties of Salt—The ordinary common 
salt of the useful arts, in all its varieties of fish- 
ery salt, bay salt, and stored salt, is obtained by 
evaporation of sea-water; and is very seldom 
pure, or even nearly pure; and often contains 
a considerable intermixture of the other salts 
which are associated with muriate of soda in the 
sea. See the article Sea-Watzr. The sulphate 
of magnesia, the muriate of magnesia, and the 
sulphate of lime which occur in it may be pre- 
cipitated as carbonates, by boiling a solution of 
it during a few minutes with a slight excess of 
carbonate of soda, and then filtering the liquid, 
and neutralizing it with muriatic acid. The dif- 
ferences which exist among the many varieties, 
arise solely from diversities in the mode of pre- 
paration; and the chief groups of the varieties 
are common British salt, foreign bay salt, and 
Dutch salt. A specimen of common Scotch salt 
analysed by Dr. Henry contained 0:4 per cent. of 
insoluble matter, 2°8 of muriate of magnesia, 1°5 
of sulphate of lime, 1°75 of sulphate of magnesia, 
and 93°55 of chloride of sodium; a specimen of 
Sunday Scotch salt contained 0°1 per cent. of in- 
soluble matter, 1:15 of muriate of magnesia, 1:2 
of sulphate of lime, 0°45 of sulphate of magnesia, 
and 97:1 of chloride of sodium; a specimen of 
common Lymington salt contained 0:2 per cent. 
of insoluble matter, 1'1 of muriate of magnesia, 
15 of sulphate of lime, 3:5 of sulphate of mag- 
nesia, and 93°7 of chloride of sodium ; a speci- 
men of cat Lymington salt contained 0:1 per 
cent. of insoluble matter, a large trace of muri- 
ate of lime, 0°5 of muriate of magnesia, 0:1 of 
sulphate of lime, 0:5 of sulphate of magnesia, and 
98°8 of chloride of sodium; a specimen of St. 
Ube’s bay salt contained 0°9 per cent. of insolu- 
ble matter, a trace of muriate of lime, 0°3 of mu- 
riate of magnesia, 2°35 of sulphate of lime, 0:45 
of sulphate of magnesia, and 96:0 of chloride of 
sodium; a specimen of St. Martin’s bay salt con- 
tained 1:2 per cent. of insoluble matter, a trace 
of muriate of lime, 0°35 of muriate of magnesia, 
1:9 of sulphate of lime, 0°6 of sulphate of mag- 
nesia, and 95°95 of chloride of sodium; a speci- 
men of Oleron bay salt contained 1-0 per cent. of 
insoluble matter, a trace of muriate of line, 0:2 
of muriate of magnesia, 1°95 of sulphate of lime, 
0°45 of sulphate of magnesia, and 96°425 of chlo- 
ride of sodium; a specimen of Dutch salt, in 
large and very small crystals, analysed by Pro- 
| fessor Traill, contained 0-065 per cent. of insolu- 
