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COP

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appears to be nearly in this ftate. By heat itbecomes brown, but regains its colour on ex-poiure to air.

Some experiments of Mr. Chenevix 1 throwfurther light on the nature of the fub-oxyd andmuriated fub-oxyd above mentioned. It wasnoticed on the analyfis of the red oCtohedralcopper ore that this fubftance was a pure oxyd,confifting of about 88.5 of metal and 11.5 ofoxygen, and therefore in a much lower ftate ofoxygenation than in any hitherto obferved. Thisore on the aftufion of nitric acid difl'olvedtherein with a rapid difengagement of nitrous gas,fhewing thereby the neceffity of a more compleatoxydation of the metal to enable it to unite withthe remaining undecompofed portion into com-mon nitrat of copper. Muriatic acid was thentried, and was added to 100 parts of the ore. Theliquor became hot and the ore difl'olved thereininto a brown fluid, but which turned green onexpofure to air. Iron feparated 88 parts ofmetallic copper, leaving only 12 for the oxygen,which in the proportions of the common blackoxyd, would only have indicated 48 of copperinftead of 88 ; but as the whole 100 parts weredifl'olved, it was proved that no part of the orecould have been a mixture of reguline copperand black oxyd, fince reguline copper is notfoluble in cold muriatic acid, and hence it ap-pears a legitimate conclufion that the red oCto-hedral ore is really a diftinct and before un-known fub-oxyd of copper. On adding waterto the concentrated muriatic folution, a verycopious white precipitate fubfided, which be-came orange on further walhing with water,and appeared to be the muriated fub-oxyd.

A fimilar muriated fub-oxyd of copper Mr.Chenevix alfo produced artificially by mixing57.5 parts of the black oxyd with 50 parts ofthe pulverulent regulus of copper obtained byprecipitation by iron, and which may readily bereduced to a fine powder. This difl'olved almoftentirely in cold muriatic acid, which is a curiouscircumftance, fince before the folution of thereguline part could have been effected, it mu fthave taken a fufficient portion of oxygen fromthe black oxyd ; and thus (the one by takingand the other by loling oxygen) both would bereduced to the ftate of a fub-oxyd, there beingno more than 11.5 of oxygen in the black oxyd,which, by this diftribution, proved fufficientto render nearly 90 parts of copper foluble.It may be here remarked that a fub-oxyd ofiron is made in a fimilar manner by mixingthe perfect oxyd with iron filings and heating' rh.Trans, for 1S01. * Mem. de 1 ’A

moderately, the refult of which is the blackfub-oxyd or ethiops of iron.

Copper appears to have a ftronger affinity forthe muriatic acid than for the nitric or even thefulphuric. Thus, according to Cornette, u ifeither the folid nitrat or fulphat of copper beadded to muriatic acid, a folution takes placewith the production of cold, and if it is heatedit immediately lofes the blue colour peculiar tothefe two fnlts, and acquires the green of themuriat. Alfo if the liquor is flowly evaporatedmuriat of copper is obtained in cryftals.

The Acetous acid does not aCt upon regulinecopper, but when oxydated it difl'olves it witheate into a fine green liquor readily cryftal-lizable. There is alfo with this, as with manyof the other cupreous (alts, a diftinct ftate offib-acid and of faturated fait. Both the fub-acetite and the acetite of copper are the producesof a domeftic manufacture carried on to a con-fiderable extent in the South of France , andtherefore require a fuller defeription: the fub-acetite being the common verdigris of the fhops(verdetJ, and the acetite, being the cryftallized,or diftilled verdigris, as it is called, (crflaux-de Venus—Vinlet cryjlallize.)

This manufacture, in its prefent fomewhatimproved ftate, is thus deferibed by Chaptal*as carried on at Montpellier .

The materials for this manufacture are, ill.Any refufe matter of the ripe grape, the ftalks,feeds, &c. but more particularly the inarc orthe cake that remains in the wine-prefs afterthe greater part of the juice has been extracted.This when fermented produces the acid requifiteto corrode the copper. 2d. Plates of copperof convenient fize and previouily hammeredwell to fmooth the furface, in order that thecorroded portion may be conveniently detached,without which preparation too much of thecopper would peel off in feales, without beingthoroughly penetrated by the acid.

The marc of the grape, which may be keptfor a good while by being dole packed in calks,is firft fermented, Amply by being laid loofelyin a large barrel, moiftened with water (or betterwith wine) and fet in a warm airy place. Aftera while, fometimes in a day, at other times intwo or three weeks, it heats, (wells, and gives aftrong fmell of vinegar, and when the ferment-ation fubfides it is fit for ufe. The richer thegrape juice of courfe the better is the marcand the more perfect will be the vfubfequentfermentation, on which much of the quality ofthe verdigris depends. Hence it ihould not bead, for 1779. ’ Ann. Cnim. tom. 15.

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