This earth is of a white colour, and of a hot caustic taste; with acids it forms peculiar salts; a fact which we shall shew affords the most decisive means of identifying its presence. It changes vegetable blues to a green, and reddens turmeric; it is capable of fusion; so great is its affinity for water, that it will absorb and solidify one third of its weight of that fluid, and yet remain perfectly dry. The heat, therefore, that is evolved in the process of slacking lime, evidently proceeds from the water, which yields its caloric, as it passes from the liquid to the solid state.
Symptoms of poisoning by Lime.
It is perhaps the least energetic of the corrosive poisons; and yet, when taken in any quantity, it will produce nausea, vomiting, colics, frequent stools, and all the symptoms which characterise, or are complicated with, inflammation of the stomach and intestines.[[332]] Lime in combination with carbonic acid is not considered as poisonous.
Organic lesions discovered on dissection.
In examining the body of an animal that has been killed by caustic lime, we shall find the mucous membrane of the stomach reddened, and evincing marks of inflammation in those parts which have been in contact with it.
Tests for the detection of Quick-lime.
We may proceed, if the substance be free from mixture, to obtain a solution of the earth in distilled water, and to assay it by the following reagents.
(a) Carbonic acid, and the soluble alkaline sub-carbonates produce a copious white precipitate, which is soluble in an excess of carbonic acid. The carbonate of lime, of which this precipitate consists, is also decomposed by muriatic acid, with effervescence, a soluble muriate remaining.
(b) Oxalic acid, and oxalate of ammonia. They precipitate lime-water of a white colour, and the resulting oxalate is not soluble in an excess of acid.
(c) Sulphuric acid. This acid does not precipitate lime water, since the sulphate of lime formed does not require more than 300 parts of water to dissolve it. Whereas, says M. Orfila, the smallest quantity of an exceedingly diluted solution of baryta becomes instantly turbid on the addition of that acid, because the sulphate of baryta is insoluble in several thousand times its weight of water. By this test, therefore, we are at once enabled to distinguish lime-water, from barytic water.