SALT. 
| salt consists mainly of two words, one generic, 
the other specific. The generic word precedes 
the specific, and is derived from the acid; the | 
specific comes from the base. For example, a 
| salt consisting of sulphuric acid and soda, is 
| spoken of generically under the name of a su/- 
| phate, and specifically, by adding the name of the 
base; thus, swphate of potash. The termination 
ate corresponds with the acid whose termination | 
is in tc, and the termination te with the acid 
whose termination is in ous; thus swphurie acid 
gives sulphates,—sulphurous acid, sulphites. There 
{ are some acids containing less oxygen than those 
that terminate in ows: in such case, the word 
hypo is prefixed; thus we have hypo-sulphurous 
acid, Aypo-nitrous acid, giving also salts that are 
called hypo-sulphites, and hypo-nitrites. When 
the salt is a compound of one atom, or propor- 
tional of acid with one of base, it is distinguished 
simply by the words denoting the acid and the 
base, without the addition of any prefix. Ifthe 
salt contains ¢wo atoms of acid united to one atom 
of base, the Latin numeral adverb dzs or 07 is 
prefixed. Thus dcseulphate of potash is a salt com- 
posed of two atoms sulphuric acid and one atom 
potash. Were there three, four, &c., atoms acid, 
the numeral adverbs ter, quater, &c., would be 
prefixed. Thus quateroralate of potash means a 
compound of four atoms oxalic acid and one atom 
of potash. When two atoms of base are com- 
bined with one atem of acid, this is denoted by 
prefixing the Greek numeral adverb dvs. Thus 
diphosphate of potash means a compound of two 
; atoms potash with one atem phosphoric acid. 
The prefixes tris, tetrakis, &c., indicate three, 
four, &c., atoms of base with one atom of acid. 
Salts of this description were formerly termed 
| sub-salis; at least in those instances where an 
| alkaline reaction was produced upon test-liquors 
from the excess of base. 
All salts, with a very few exceptions, are solid ; 
| and most either have naturally the form of crys- 
|| tals, or assume that form by the slow evapora- 
| tion of their aqueous solutions. Some are soluble 
| in water, and more or less sapid ; and others are 
| insoluble and completely insipid. One, the car- 
| bonate of ammonia, emits an exceedingly pun- 
| gent odour, and has popularly the name of smell- 
| ing salt; butalmostall the cthersare totally odour- 
| less. Some have brilliant colours, and others have 
| none; and some are transparent, others semi- 
pellucid, and others opaque. All which consist 
{ of a colourless acid and a colourless base, are 
| themselves colourless ; and some also which con- 
sist of a coloured acid or a coloured base are col- 
} ourless; and many which consist of coloured 
| constituents and are themselves coloured, pos- 
| sess entirely different colours from those of their 
| constituents. Some have a powerful affinity for 
| water, and attract so much moisture from the 
atmosphere as to deliquesce or become liquid ; 
others remain unchanged under a dry atmo- 
sphere, but become moist under a humid one; 
119 
and others show such indifference or resistance 
to water as to suffer no change from exposure to 
an atmosphere loaded with vapour. Some of the 
soluble salts dissolve in less than their own 
weight of water; and others do not dissolve in 
less than dozens or scores or even hundreds of 
times their own weight of water. Many salts, 
in the process of crystallizing, combine with 
themselves a definite portion of water, which is 
essential te their crystalline state, and bears the 
name of the water of crystallization ; and some 
of these contain more than half of their own 
weight of this water, and yet are perfectly dry,— 
all lose the whole of their water when exposed to 
a strong heat,—and some, such as the sulphate of 
soda and the phosphate of soda, lose a portion of 
their water and crumble down into powder, or 
are said to effloresce, when merely exposed for 
some time to the air. Salts which do not take 
water freely into combination with their crystal- 
line constitution, often enclese particles of it 
among the interstices of their crystals; and 
when heated, they are rent asunder by the ex- 
pansion of these particles, and in consequence 
burst with a crackling noise, and are said to de- 
crepitate. Several different salts which do not 
decompose one another may be held in solution 
by the same quantity of water which is merely 
sufficient to dissolve one ; and, in some instances, 
two different salts, in consequence of their mu- 
tual combination, are soluble in less water than 
would suffice for the separate solution of either. 
Most salts produce cold during the process of 
solution ; and those which contain water of crys- 
tallization produce more than those which con- 
tain none; and any produce more when dissolved 
rapidly and in large quantity than when dis- 
solved slowly and in small quantity. All salts, 
either in a state of solution or in a merely moist- 
ened state, are decomposed by voltaic electricity. 
The solubility of the soluble salts in water is one 
of their most important general properties. In 
this menstruum they are generally crystallized ; 
and by its agency they are purified and separated 
from one another, in the inverse order of their 
solubility. The determination of the quantity of 
salt which water can dissolve, is not a very diffi- 
cult process. It consists in saturating the water 
exactly with the salt, whose solubility we wish 
to know, at a determinate temperature, weigh- 
ing out a certain quantity of that solution, eva- 
porating it, and weighing the saline residue. 
We shall give the results of some experiments 
upon the solubility of a few salts. 
Sulphate of Soda. 
Salts soluble in 100 parts of water. 
Temperature. Anhydrous, Crystallized. 
0:60° 5°02 12°17 
11 67 10°12 26°38 
17°91 16°73 48°28 
28°76 37°35 161°53 
30°75 43°05 215°77 
82°73 50°65 322°12 
