O X A

O X A

( 1.90 )

the oxalic, and if the former is in fufficientquantity, and the mixture long boiled, muchnitrous vapour is given out, no oxalic acid isfound in the liquor, but the whole is convertedinto carbonic acid and water.

The muriatic and acetous acids limply diffolve. the oxalic, but do not decompofe it.

The compofition of this acid according toT’ourcroy and Vauquelin, is 77 per cent, of oxy-gen, 13 of carbon, and 10 of hydrogen, fothat it appears to be one the moft oxygenatedof all the known acids.

Before we proceed to defcribe the falts whichit forms with the different bafes, fome obferva-tions may be added on the circumltances of itsformation.

The oxalic acid is found but rarely native, butis readily produced by the adfion of nitrous acidon almoft every foluble vegetable matter, andmolt animal matters. During this a£tion thenitric acid is obvioufly decompofed, and muchnitrousgas given out,and hence the product multcontain much of the oxygen which the nitricacid parts with. But it appears that the forma-ation of oxalic acid is not in any cafe a Ampleoxygenation of carbon and hydrogen, but amuch more complicated operation, in whichaccording to well-eftabliffied laws of affinity,fpecilic proportions of carbon and hydrogenunite with a certain portion of oxygen toform oxalic acid, whilft at the fame time otherportions of the fame bafes form different pro-duffs. Hence it is inaccurate to ftate as isfometimes done, that fugar is the bafe of theoxalic or faccharine acid, fince it is a compoundof hydrogen and carbon derived from the fugar,and which the action of the nitrous acid cauiesto be feparated in the proportions neceffary forthat purpofe. Hence the utmoft aftion of thenitric acid on oxalic acid differs from thatwhich it exerts on l'ugar, for in the former cafeonly carbonic acid and water are formed,whereas in the latter there is generated a quan-tity of acetous acid.

The Mnl c Acid appears to be produced alongwith the oxalic, in almoft every inftance yetexamined, and it forms the greater part of themother liquor, or fluid part from which' theoxalic feparates by cryftallization. The malicacid is alio chiefly (but probably not entirely)convertible into oxalic by the further adtion ofnitrous acid, and hence it is in fome lenfe anintermediate ftate between oxalic acid and theliydro-carbonous bafe previous to oxygenation.This is fliewn by many experiments of Scheele .

Journ. de Phyf.

This excellent chemift diftilled equal parts ofnitric acid and fugar, b flopping the procefswhen the mixture in the retort had acquired abrowniffi colour, which indicated that all theacid was decompofed. The liquor was acidand of a fyrupy confiftence: on adding lime-water, fome oxalic acid feparated in the formof oxalat of lime. The remaining liquor wa*then faturated with lime (which occafioned nofurther precipitation) after which it was coagu-lated by alcohol, the coagulum decompofed byacetite of lead and fulphuric acid (in the waydeferibed under the article Malic Acid ) and "aquantity of pure malic acid was produced. Onthe other hand when the proportion of nitricacid is much greater, the product of oxalic acidincreafcs, and that of malic diminiffies.

The fame excellent chemift found gum-arabictreated with nitric acid, to yield a mixture ofmalic and oxalic acid (fee the article Mucilage).Manna, the fame; fugar of milk the fame, to-gether with the faccholaftic acid (fee Milk).Salep the fame, together with oxalat of lime ;aloe, colocynth, and fome of the refinous gumsthe fame, but in fmaller quantity; many of thevegetable extradls the fame, together with fomeoxalic acidulum, or fuper-oxalat of potaffi (thepotaffi being doubtlefs furnifhed from the acetiteof potaffi which V auquelin has found to exiftin extradls). Of the effential oils only that ofparlley could be made to furniffi thefe acids,which it did in abundance, and was totallyrefolved into them.

Several animal matters were then treated withnitric acid in the fame way. On one part ofglue were poured two of nitric acid, muchnitrous vapour was given out on heating, theglue was diffolved, and the next day cryftals ofoxalic acid appeared in the liqour. The uncry-ftallized refidue faturated with chalk, and treatedwith acetite of lead and fulphuric acid, gavethe malic acid. Ilingials, the white and yolkof egg, and blood, gave the fame products.During thefe procefles with animal matters, asthis excellent chemift obferves, a quantity ofthick greafe feparates, little nitrous gas orcarbonic acid is given out, but an abundance ofvitiated air (azot). Another remark equallyimportant is that whenever the. oxalic acid isproduced by the a&ion of the nitric on animalor vegetable fubftances, a quantity of acetousacid is found in the receiver, mixed with thediftilled nitrous acid. This latter difeoveryappears to have been made nearly at the fametime by Scheele and Weltrumb.

tom. »8. p. 4i2<