Part 4

It has never as far as I know been met with diſengaged, unleſs perhaps in water precipitated out of the atmoſphere, but is found united to alkalies (§§ 45, 47, 51 ) or to earths (§§ 60, 64.)

§ 29.

Muriatic ACID (ſpirit of ſalt) is found in great quantity at and under the ſurface of the earth. The ſtrongeſt prepared by art hardly attains a ſpecific gravity of 1, 150. It has a very peculiar and volatile ſmell. Deprived of its ſuperfluous water it aſſumes an aerial form, for phlogiſton ſeems to be one of its conſtituent parts.

It has never been found uncombined (unleſs perhaps like the nitrous acid in water precipitated from the atmoſphere) but united to alkalies (§§ 46, 49, 52), to earths (§§ 61, 65), or to metals (§§ 74, 161, 175, 191).

§ 30.

Fluor ACID, is obtained by art; its ſpecific gravity never exceeds 1,500, it is very volatile. Its vapours when hot, corrode glaſs; and meeting with moiſture generate, or at leaſt depoſit ſiliceous earth. When deprived of its ſuperfluous water it aſſumes an aerial form. It has never been found diſengaged, but united to calcareous earth forming ſparry fluor (§ 96) and if I am not miſtaken it enters into the compoſition of ſiliceous earths.

§ 31.

Arſenical ACID, dry; prepared by art; ſpecific gravity 3,391; fuſible and fixed in the fire, until it acquires from the matter of heat ſo much phlogiſton as is neceſſary to convert it into white arſenic. In a moiſt air it deliqueſces.

It is not found uncombined, but united to calx of cobalt (§ 228), and alſo to phlogiſton, forming a brittle arſenical metal (§ 220), and its calx (§ 222).

§ 32.

Molybdæna ACID. This is very probably of metallic origin, though it does not yet appear to which metal it belongs. Seeing that arſenic, a brittle metal, by dephlogiſtication only is changed into an acid, different from all other acids, it is not improbable that other metals may have an acid baſis, although their phlogiſton adhering more ſtrongly has not yet been completely ſeparated.

How this ſubſtance may be obtained by art does not belong to this place to deſcribe; but that the acid got from Molybdæna has a metallic nature, and as yet has not been perfectly freed from phlogiſton, is probable from the following conſiderations. 1, Its taſte is acid and at the ſame time metallic. 2, Microcoſmic ſalt and borax are coloured by it, and theſe ſalts are hardly coloured by any thing but metallic calxes. 3, Its decompoſition by means of the phlogiſticated fixed alkaly, which always indicates the preſence of a metal. 4, Its concrete form, and not deliqueſcing, analogous to white arſenic. 5, Its ſpecific gravity 3,460. And very lately M. HIELM by my perſuaſion attempted the reduction and obtained a regulus, ſeemingly different from every other metal, but not yet ſufficiently examined.

§ 33.

An acid conjoined to the calx ponderoſa (ponderous calx or lime) is nearly allied to the preceding, but dropped into lime water produces a different compound, though in a number of other circumſtances theſe two acids agree. I apprehend that this is likewiſe of a metallic nature.

§ 34.

Phoſphoric ACID, evidently exiſts in the animal kingdom, much more plentifully in the vegetable, but in the foſſil very rare. Mr. J. G. GAHN firſt detected it united with lead; but probably it may be found in many other foſſils. It is fuſible in the fire. Its ſpecific gravity when deprived of water 2,687.

§ 35.

Boracic ACID, (acid of borax, or ſedative ſalt.) Many people ſtill think this to be an artificial production, but not long ſince Mr. HOEFER found it in a lake near Sienna in the great dutchy of Hetruria, and it has long been known to be united to the foſſil alkaly in native borax. It acts like an acid, though very feebly. It melts in the fire and volatilizes with water. Its ſpecific gravity is 1,480.

§ 36.

Amber ACID, is a concrete ſalt obtained from amber; it acts like a feeble acid. It is yet doubtful whether amber be of vegetable origin; many reckon it foſſil.

§ 37.

Aerial ACID (fixed air) is not only combined with water but with many other foſſil ſubſtances, as alkalies (§§ 54, 56), earths (§§ 62, 66), and with ſome metals (§§ 71, 183, 192, 217, 234, 243). It floats uncombined in the atmoſphere. Its ſpecific gravity 0,0018.

§ 38.

ALKALIES are known by their peculiar lixivial taſte, by their vehement attraction to acids, and by their changing the blue colours of vegetables to a green. In a pure ſtate, as was before obſerved of acids, their attraction to other ſubſtances is ſo ſtrong that they cannot long remain uncombined; and if other acids were wanting, the aerial acid, every where preſent in the atmoſphere, would unite with them: therefore they are always found in a ſtate of combination, unleſs prepared by art.

§ 39.

New acids are daily detected, but no additions have been made to the three ſpecies of alkaly long ſince known.

§ 40.

Vegetable fixed ALKALY, deprived of every acid is not found on the face of the earth; but it is ſometimes met with in combination with the vitriolic acid (§ 44) or the muriatic (§ 46), generally with the nitrous, (§ 45) rarely with the aerial (§ 54).