157
Ac'idum Ni'tricum.—Nitric Ac'id.
History and Synonymes. —This acid was known in the seventh cen-tury to Geber , who termed it solutive water, {Of the Invention of Verity,ch. xxi. and xxiii.) The nature of its constituents was shown by Caven-dish in 1785, and their proportions were subsequently determined byDavy, Gay-Lussac , and Thomson. It has been known by various names,as Glauber’s spirit of nitre , and aquafortis.
Natural History . —It is found in both kingdoms of nature.
{a.) In the inorganized kingdom,.• —Combined with potash, soda, lime,or magnesia, it is found on the surface of the earth in various parts of theworld. The nitrates have been found in some few mineral waters. Thus‘here is a district of Hungary, between the Carpathians and the Drave,where all the springs, for the space of about 300 miles, contain a smallquantity of the nitrate of potash (Gairdner, on Mineral Springs , p. 20).
{b.) In the organized kingdom. —Nitrate of lime has been found inBorago officinalis, Urtica dioica, Helianthus annuus , and Parietaria offici-nalis. Nitrate of potash has been detected in the roots of CissampelosPareira, and Geumurbanum; in the juice of Chelidonium majus ; in Apiumgraveolens ; and sometimes in the root of Beta vulgaris when advanced inage. The same salt is also found in the flowers of Verbascum , in therhizome of Zingiber officinale, in the fruit of Areca Catechu, in the tuber-cle of Cyperus esculentus, in Agaricus acris, and A. edulis (Decandolle,Physiol. Veget. t. T r . pp 383, 387, and 403).
Preparation, (a.) In the Pharmacopoeia . —In the London Pharmaco-poeia we are directed to mix in a glass retort two pounds of dried nitrateof potash with an equal weight of strong liquid sulphuric acid, and todistil the nitric acid in a sand bath. Mr. Phillips {Translation of thePharmacopoeia ) says that this process yields nitric acid of sp.gr. 1'5033to P504.
The explanation of the changes which take place is somewhat modi-fied by the strength of the sulphuric acid employed. According to Mr.Phillips, the acid usually met with has a sp. gr. of 1‘8433: I have foundit generally somewhat below this. The acid alluded to by Mr. Phillipsis composed, according to the same authority, very nearly of four equi-valents or 160 parts of dry sulphuric acid, and five equivalents or 45parts of water. These quantities re-act on two equivalents or 204 partsof nitrate of potash, and produce two equivalents or 135 parts of strongliquid nitric acid (sesquiliydrate), and one equivalent or 274 parts of thehydrated bisulphate of potash.
INGREDIENTS USED.
PRODUCTS.
2eq. Nitr te . Pot h . . 204
4 eq.Liq d .Sulp c .Acid205(Sp. gr. 1*8433)
trie Acid. 108tash ... 96ater ... 27 -ater ... 18
2 Sesquihydrate Nitric Acid 135
'/$L-
2 Hydrated^Sulphate Potash 274
Instead of the glass retort directed in the Pharmacopoeia , manufacturersgenerally employ an iron or stone-ware pot, with a stone-ware head,which is connected with a row of double-necked stone-ware bottles.(See fig. 41, p. 158).
{b.) For commercial purposes. —The ordinary nitrous and nitric acidsof commerce are prepared in an iron cylinder set in brickwork over a