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).