A Treatise on Calico Printing, VOL. I-II
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1792Saline substances are combinations of earths and water, or they are combinations capable of uniting with either of them, or with both to gether, for all salts are resolvable into earth and water, and the more or less they are united to their earths, they are fixed or volatile, which circumstance makes the difference between acids and alkalies. Acids are the simplest of salts, uniting readily with water, are. sharp to the taste, and have the distinguishing property of turning vegetable blues and violets red.
Alkalies have a greater proportion of earth than acids have, and have less affinity with water, but unite violently with acids, producing an effervescence and hissing; they are fiery and acrid to the taste, and turn vegetable blues and violets green.
Neutral Salts are formed from the union of art acid and alkali, by which union they rob each other of its properties, which are then so blended that neither predominates, and which intimate union is called the point of saturation: they produce no change in the blue colours of vegetables, and are neither acrid or four, but salt, such as is the taste of kitchen salt, and are generally known by the plain general term of salts. Imperfect neutrals are those in which either the acid or alkali predominate.
Of the universal or vitriolic Nitrous and Marine Acids.
The universal acid, according to its name, is found diffused in the waters, in the atmosphere, and in the bowels of the earth, but seldom pure or unmixed with other substances; what the greatest quantity is collected from is vitriol, hence it is called the vitriolic acid; and when it contains only just phlegm enough to give it a fluid form, it is called oil of vitriol; if it contain much water, it is called spirit of yitriol; when it has not enough to render it fluid, it is called the icy oil of vitriol.
This acid combined with a certain absorbent earth, with the nature of which we are unacquainted, forms a neutral salt called allum; differing in quality according to the earths with which the vitriol is combined: An alkali being presented to allum, the acid will quit the earth and join the alkali, and from the junction of the vitriolic acid, with a fixt alkali, a neutral salt is formed, called either arcanum duplicatum, or vitriolated tartar, one of the fixed alkalies most in use, being salt of tartar. — See Maddering, and note 27.
The conjunction of this acid with phlogiston forms sulphur.
Nitrous Acid.
This is no other than the vitriolic acid combined with phlogiston, by the agency of putrefaction, at least such is the received opinion, the nitrous acid being found only in earths and stones, impregnated with matters to putrefaction; when combined with chalk, stone, marble, &c. it forms a salt, that does not chrystalize, which runs in the air, per deliquium, and is de composed by fixed alkalies, with which the acid unites and quits the earths, and from this union results salt-petre.
The most remarkable and distinguishing property of nitre is its disposition to unite with phlogiston, in its purest state, such as charcoal, sulphur and metallic substances; thence bursting into a flame with great noise, called its detonation or deflagration, in which case the acid is dissipated, and the alkali which is left is called fixed alkali.
A nitre isto be procured by dropping into spring water, a solution of fixed alkaline salt, filtrating the liquid and evaporating it to a certain degree.
Marine Acid or Sea-Salt.
In respect to the constituent parts of this acid, wherein it differs from the vitriolic and nitrous, it is not certainly known, no more than it is wherein they disfer from each other; but when combined with absorbent earth (lime or chalk) it forms a neutral salt, that does not christalize, and when dried, attracts the moisture qf the air: This acid, like the others, has less affinity with earths than with fixed alkalies, but as well as the others have, it has a greater with phlogiston; and when combined with fixed alkali it forms a neutral salt which shoots into cubical chrystals, and is inclined to run in the air.
The acid of this salt when freed from its basis, is called spirit of salt, and when containing little phlogiston, it is called the smoaking spirit of salt, from its then continually emitting vapours.
Combined with phlogiston, a kind of sulphur is the result, that takes fire on being exposed to the air, called phosphorus of urine, being generally prepared from urine.
India supplies us with another acid called bo rax, which flows and takes the form of glass, and possesses some of the properties of fixed alkali.
Lime.
Any substance that has been roasted in a strong fire without melting, is called a calx; stones, (which are substances composed of different earths) reduced to this state is called lime; this applied to fixed alkalies make them more active and renders them corrosive or caustic, and from which the common caustic stone is prepared: Lime unites with all acids, and chrystalizes with the marme, but not with the nitrous.
Quick lime attracts the air like concentrated acid, and dry fixed alkali, but not so as to render it fluid; it only takes the form of a powder, and is then called slacked lime; when once slacked, though it seem ever so dry afterwards, it requires a violent calcination to separate the water from it, which it had imbibed. Sand is mixed with it in making mortar, or it would otherwise contract and consequently crack and break.
In Chemistry it is deemed holding a middle rank between absorbent earths and fixed alkalies.
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