Soda.
We have already stated by what chemical reagents this alkali may be distinguished from potass; it only remains for us to observe that its physiological action, the symptoms arising from its ingestion, and the organic lesions discovered on dissection, are strictly analogous to those we have described as the effects of potass.
Ammonia, and its Carbonate.
Ammonia, in its uncombined state, exists in the state of gas, and is incapable of application; its affinity, however, for water, enables it to combine with that fluid, and to form liquid ammonia, (Liquor Ammoniæ) in which state it is useful in medicine, and in the arts. This solution is colourless; its taste extremely caustic; and its odour strong, pungent, and peculiar. Exposed to the action of heat, the ammoniacal gas is driven off, and may be recognised by its characteristic odour, as well as by its effects upon moistened turmeric paper. When brought into contact with muriatic acid, it will form dense white vapours, consisting of muriate of ammonia. A most elegant and sensible test for ammoniacal gas is afforded by a mixed solution, consisting of arsenious acid and nitrate of silver; these substances when mixed in solution do not occasion the least disturbance in each other, for reasons already explained, (see page [240]) but upon spreading a portion of the liquid upon glass or paper, and bringing ammoniacal gas into contact, a beautiful yellow cloud immediately diffuses itself over the surface of the solution.
Sub-carbonate of ammonia occurs in solid, white, semi-transparent masses, of a highly pungent and ammoniacal odour. Its chemical composition has been found to vary materially according to the circumstances under which it has been prepared; Mr. R. Phillips, who has made some highly interesting experiments upon this subject, considers the sub-carbonate to be a sesqui-carbonate, composed of 3 atoms of carbonic acid, 2 atoms of ammonia, and 2 of water. By long exposure to the air, its pungency is lost, and it is converted into an inodorous carbonate.
Symptoms of poisoning by Ammonia.
Cases wherein death has been produced in a few minutes, from the ingestion of liquid ammonia, stand recorded on the authority of Martinet, Huxham, Haller, and other physiologists. In such cases the lips, tongue, and fauces are described as being burnt by the causticity of the fluid; while hemorrhage of the intestines marks the organic lesions which it occasions. The nervous system would appear also to suffer greatly, at the same time that the abdominal organs are affected with violent inflammation.
The Caustic Alkaline Earths.
Under this division, we have to consider the two earths, Lime and Baryta; both of which are highly corrosive, although they essentially differ from each other in their physiological action. In this respect they may be compared to corrosive sublimate and arsenic, and offer an additional illustration of the imperfection of the present classification; for while lime acts as a local caustic upon the parts with which it comes in contact, baryta will require, for its action, to be absorbed and carried into the current of the circulation.