res — = a 
118 
respective metals; that they are formed, not by 
the alkalies and the oxides taking the place of 
the water of a hydrated sulphuric acid, but by 
the metals of these bodies taking the place of 
the hydrogen of a dry or anhydrous sulphuric 
acid; that they arise, not out of an acid com- 
pound of one equivalent of water and one equiva- 
lent of a body consisting of one atom of sulphur 
and three atoms of oxygen, but out of an acid 
compound of one equivalent of hydrogen and 
one equivalent of a body consisting of one atom 
of sulphur and four atoms of oxygen; and that, 
therefore, they differ from common salt only in 
having a compound radical, sulphur and oxygen, 
instead of the simple radical chlorine,—a body 
which, after all, may possibly prove to be as 
really a compound as the analogously acting 
body, cyanogen. “It may be stated,” says Dr. 
Gregory, “that although the body consisting of 
one atom of sulphur and three atoms of oxygen 
exists, 1t is not truly an acid, and does not ac- 
quire acid properties until it has been in contact 
with water, and combined with it, that is, with 
hydrogen; that, with ammonia, this body does 
not form sulphate of ammonia, but an entirely 
different compound; that, although the supposed 
radical, consisting of one atom of sulphur and 
four atoms of oxygen, is unknown in a separate 
form, the same objection may be made to the 
older view in the case of nitric acid and many 
other acids,—for strong nitric acid is viewed as 
a hydrate of dry nitric acid, while dry nitric 
acid is quite unknown ina separate form; that 
those oxygen acids which exist without hydro- 
gen, such as dry sulphuric acid, dry phosphoric 
acid, carbonic acid, silicic acid, and chromic 
acid, either have no acid properties till water is 
added, as in the case of dry sulphuric acid and 
dry phosphoric acid, or possess very feeble and 
ill-marked acid properties, as in the case of car- 
bonic and silicic acids, which cannot neutralise 
the alkalies, and form with them an almost un- 
limited number of compounds; and that all those 
oxygen acids which possess in perfection the 
acid character, such as oil of vitriol, nitric acid, 
phosphoric acid in its active state, and the whole 
of the organic acids, invariably contain hydrogen 
in a form in which it is replaced by metals in 
the salts, or, according to the older view, water, 
which in the salts is replaced by metallic oxide. 
Now, as in water and metallic oxide, the oxygen 
is the same, it is, even on that view, hydrogen 
which is replaced by metal, when an acid is con- 
verted into a salt. It may be added, that con- 
siderations derived from the phenomena of gal- 
vanic decomposition, from the heat developed 
when bodies combine to form salts, and from the 
molecular or atomic volume of acids and salts, 
all concur to render it probable that oxygen 
acids are hydrogen compounds, not hydrates, and 
that oxygen salts contain a metal united to a 
radical, and not an oxide united to a dry or an- 
hydrous acid.” 
eee eee 
SALT. 
The old theory, however, though less consistent 
and far less beautiful and less simple to the well- 
informed chemist than the new one, is really 
plainer and more useful to the farmer and the 
general thinker; it also figures exclusively in 
all the best chemical works down to a very recent 
period, and at the same time occupies a place 
by the side of the new theory in the formule of 
even the most recent chemical writings; and 
it has far too firm a hold of both the nomencla- 
ture and the discussions of general chemistry, 
whether in itself or in its connexions with agri- 
culture, to be conveniently shaken off by any but 
complete adepts in chemical science. It likewise 
offers an easy rule for classifying all the true 
salts, according to either their base or their acid, 
or for readily comparing the saline combinations 
of each complicated acid, and those of each oxide 
and of each alkali, as well as those of each simple 
acid and those of each metal; and it conveniently 
leaves all other salts than the true ones to be ar- 
ranged into the two supplemental groups of ha- 
loid salts and sulphur salts. 
The groups of true salts, as arranged aceord- 
ing to their acids, need not amount to more than 
six, and yet possess very distinct characters of 
classification. One group comprises the sulphates, 
sulphites, hyposulphates, and hyposulphites; a 
second comprises the nitrates, the nitrites, the 
chlorates, the iodates, and the bromates ; a third 
comprises the phosphates, the pyrophosphates, | 
the metaphosphates, the phosphites, the arseni- 
ates, and the arsenites; a fourth comprises the 
chromates, the borates, and the fluo-borates ; a 
fifth comprises the carbonates ; and a sixth com- 
prises the hydrochlorates, the hydriodates, the 
hydrobromates, the hydrofluates, the hydrosul- 
phates, the hydroselianates, the hydrocyanates, 
the ferrocyanates, and the sulphocyanates. Ha- 
loid salts, in addition to simple haloids, comprise 
acid haloids, each composed of a simple haloid 
and the acid of its radical, and also oxyhaloids, 
each composed of a simple haloid and an oxide 
of the same metal as its base. 
double sulphurets, and present a pretty close re- 
semblance to true salts; and they have been 
classified into hydrosulphurets, carbo-sulphurets, | 
arsenio-sulphurets, and molybdo-sulphurets. The | 
total number of known salts amounts to several 
thousands ; and the proportion of these which 
play a conspicuous part in the natural chemistry 
of the soil, and of manures, and of vegetation, 
and of the animal functions, is very great. 
salts combine with one another, so as to form 
double salts ; and they may consist either of one 
acid and two bases, or of two acids and one base, 
or of two acids and two bases; but the great 
majority consist each of one acid and two bases. 
The early names of the salts, so far as these 
bodies were known to chemists, were wholly des- 
titute of scientific precision. At present, how- 
ever, they are universally designated according to 
the nomenclature of Morveau, The name of each 
Sulphur salts are” 
Some | 
