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The quantity of muriatic acid was deter-mined by nitrat of filver. The watery folutionof muriated copper, when fufficiently dilute,thalces a kind of fympathetic ink, which iscolourlefs in the cold, becomes yellow bywarming, and again lofes its colour on cooling. r

Chemiftry is further indebted to the ingeniousrefearches of Prouft for the difeovery of anotherfpecies of muriat of copper, in which the metalappears to be lefs oxydated than in that alreadydescribed, which makes a nearly colourlefs folu-tion, and when folid is of a greyilh-white. Itis therefore termed for diltinftion the whiteinuriat of copper, and was firft noticed ininveftigating the remarkable difoxydating pro-perties of the muriat of tin. s

Moll of the falts of copper, and the muriatin particular, if combined with muriat of tin^recently made, undergo a remarkable change.The latter fait, on account of its extremeattraction for oxygen, robs the cupreous fait ofa portion, and reduces it to the ftate of a mu-'riated oxyd which collects at the bottom of theveffel, and is white at firft, but by expofure tolight pafles to the different fhades of blue, violetarid black. In this ftate it melts in the firelike luna cornea. This white muriat (or moreproperly muriatedfub-oxyd), if heated with mu-riatic acid, diffolves therein, and cryftallizes,by cooling, in tetahedrons. With nitric acid,fome nitrous gas is given out, as with reguline' copper and this acid, which {hews that the fub-oxyd decompofes a portion of the acid in order' again to faturate itfelf with oxygen. Thefolution is nitro-muriat of copper. Anotherremarkable character of this white muriat is,that when diffolved in ammonia it is not at firftblue, as all the other ammoniated folutions ofcopper are, but quite colourlefs, as long as keptfrom the external air.

The white muriat formed as above men-tioned by the folution of tin, when analyzed byfolution in nitric acid, precipitation by nitratof filver for the quantity of muriatic acid, andby an alkali for the metallic part, gave asfellows.

Muriatic acid 24.75

Oxyd of tin 1.

Metallic copper 63.

Remains for oxygen 11.25

100.0

A {Turning this analyfis as correct, it is obviousthat the copper exifts in a much lower ftate of

• Gren. “An.

oxygenation m this fait than in any hithertomentioned, for in this, the oxyd of copper iscompofedof 63 of copper and 11.25 °f oxygen,or (reduced to the hundred) of 84.84 of copperand 15.16 of oxygen : whereas the Black oxyd, towhich all the common cupreous falts are redu-cible by lofs of their acid and water, confifts of80 per cent, of copper and 20 of oxygen. Theformer therefore is properly diftinguilhed as a-fub-oxyd, and when combined with muriaticacid, as the white muriat, may be termed themuriatedfub-oxyd.

The reader will now underhand what takesplace on diitilling the common green muriat ofcopper without addition. The firft effedb is toexpell merely any excefs of acid and the waterof cryftallization, after which, by encreafing theheat, oxymuriatic acid comes over, (compofedof the proper acid of the fait, and the quantityof oxygen which makes the difference betweenthe perfect oxyd and the fub-oxyd) and a greymelted mafs remains, which is chiefly the whitemuriat, or muriated fub-oxyd.

When this is expofed to the air for a day ortwo, it is again converted into the commongreen muriat. Part of the copper is itfelf vo-latilized, however, as is feen by the beautifulblue-green flame which the heated muriat givesto any burning matter.

There appears to be yet another ftate of com-bination of muriatic acid alfo noticed by Prouft.It is the fub-muriat of copper, or a fait that dif-fers from the common muriat, not by a lowerdegree of oxygenation of the metal, but in aninferior proportion of muriatic acid. It is pro-duced by adding a little potafh, (lefs than tofaturation), to the green muriat. A greenpowder falls down, which is the fub-muriat,and correfponds with the fub-nitrat alreadydeferibed. If an excefs of potafh is added, thefait is entirely decompofed, and the precipitateis the hydrat.

This fub-muriat boiled with potafh lofes about28 per cent, of its weight, and is reduced to theBlack oxyd. A fimilar fub-muriat is faid by thefame chemift to be fpontaneoufly -depofitedwhen copper is diffolved in nitro-muriatic acid,and its compofition is given as follows:

Black oxyd of copper 79Muriatic acid . 12.5

Water . . 8.5

100.0

The green native muriat of copper of Peru <te Chim. tom. 28.