_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. QUICK LIME. 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._