We begin with the nature and properties of ſaline bodies, for unacquainted with theſe our knowledge of other bodies muſt be exceedingly imperfect. Native ſalts are either acid, alkaline, neutral, earthy or metallic.
Acids may be diſtinguiſhed by their proper taſte; they efferveſce with mild alkalies; and change the blue juices of vegetables and tincture of heliotropium to a red colour[6].
We are acquainted with many ſpecies of acids, but they are hardly ever found pure in the bowels of the earth, nor can we expect to find them ſo when we conſider how ſoon ſuch powerful menſtrua muſt meet with ſubſtances to ſaturate them. Their great abundance and their properties ſhew their various and indiſpenſible uſes in the œconomy of nature.
As mineralogy treats of thoſe bodies which are found under the ſurface of the earth, and as acids in an uncombined ſtate are not found there, it would ſeem proper to exclude them; but the ſame reaſon would likewiſe exclude the primitive earths, ſome of which have never yet been found pure. Therefore in a ſyſtem formed upon the component parts of bodies, a ſhort deſcription of the principal of theſe is not to be diſpenſed with, although they hardly ever preſent themſelves in a ſeparate ſtate.
Vitriolic ACID. When moſt concentrated by artificial means its ſpecific gravity is 2, 125. When pure, has neither colour nor ſmell. Cold ſometimes though very rarely concretes it into a ſolid form; it may be coagulated by nitrous air. This as well as the other acids is beſt known from the compounds it forms with other ſubſtances.
Mr. Vandelli[7] ſays that it is ſometimes mixed with the ſtreams from the hills in the neighbourhood of Sienna and Viterbo, raiſed no doubt by ſubterranean fires; but in general it is united to alkalies (§§ 44, 47, 50,) to earths (§§ 58, 59, 63, 67,) to metals (§§ 69, 70, 72, 73,) or to phlogiſton (§§ 134, 136.)
Phlogiſticated vitriolic ACID (volatile vitriolic acid) is frequently thrown out by the craters of volcanoes; its ſmell ſuffocating and penetrating. The union to phlogiſton and the matter of heat gives it an aerial form, but does not prevent its union with water.
Nitrous ACID is by ſome excluded from the foſſil kingdom, becauſe they ſuppoſe it to be produced from the putrefaction of organic bodies. But theſe bodies when deprived of life are again received amongſt the foſſils, from whence their more fixed parts were originally derived.
In the moſt concentrated ſtate that art can procure it, its ſpecific gravity is 1, 580. Colourleſs when pure; but its ſtrong attraction to phlogiſton renders particular management neceſſary to procure it ſo[8]. With different proportions of phlogiſton it forms phlogiſticated acid and nitrous air.
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.)
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[9].
It has never been found uncombined (unleſs perhaps like the nitrous acid in water precipitated from the atmoſphere[10])[11] but united to alkalies (§§ 46, 49, 52), to earths (§§ 61, 65), or to metals (§§ 74, 161, 175, 191).
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[12]. It has never been found diſengaged, but united to calcareous earth forming ſparry fluor[13] (§ 96) and if I am not miſtaken it enters into the compoſition of ſiliceous earths.
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).
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[14]; 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.
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.
Phoſphoric ACID, evidently exiſts in the animal kingdom,[15] much more plentifully in the vegetable, but in the foſſil very rare. Mr. J. G. Gahn firſt detected it united with lead;[16] 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.
Boracic ACID, (acid of borax, or ſedative ſalt.) Many people ſtill think this to be an artificial production, but not long ſince Mr. Hoefer[17] 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.
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.
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[18].
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.
New acids are daily detected, but no additions have been made to the three ſpecies of alkaly long ſince known.
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).
Foſſil fixed ALKALY is only found in combination with acids, rarely with the vitriolic (§ 47) or nitrous (§ 48), principally with the muriatic (§ 49) or aerial (§ 55).
Volatile ALKALY is frequently found in clays, doubtleſs in a mild ſtate, for the help of art is required to render it cauſtic. It is alſo found united to the vitriolic (§ 50) and the muriatic acids (§ 52.)
ACIDS united to alkalies form NEUTRAL SALTS. Theſe diſſolved in water are no ways diſturbed by the addition of an alkaly, and generally by evaporation concrete into cryſtals. If by proper teſts they ſhew neither acid nor alkaline properties they are ſaid to be perfect neutrals, but imperfect when from defect in quantity or ſtrength of one ingredient the peculiar properties of the other more or leſs prevail.
We now proceed to conſider the native ſalts of both kinds.