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.