C OP
GOP
C 33S )
The oxyds of copper diflolve equally m nitricacid, but without the produdlion of gas. Whenthe folution is haftily evaporated to a certain-point, and fuffered to cool, it congeals into adeep-blue faline mafs, which again redillblvesfpontaneoufly, if kept expofed to air. A flowcareful evaporation gives this fait in the formof flx-fided prifms, but very deliquefcent andintenfely acrid. If this blue nitrat be evaporatedbeyond the point at which it would cryftallizewhen cold, nitrous gas comes over, and a greenfcaly concretion begins to feparate from thethick blue liquor, and incrufts the infide of theretort. If the diftillation is here flopped, thisgreen concrete may be feparated by water whichdifiolves only the flill undecompofed blue nitrat,and does not touch the other. Prouft confidersthis green fubflance as a fub-nitrat of copper, orhaving a deficiency of acid, to which it owes itsinfolubility in water, hot or cold, and its pecu-liar properties. It is proved to be flill a nitrat,by giving out this acid when the fulphuric isadded. By thorough calcination all the acidand water are expelled, and the black oxyd ofcopper alone remains, which weighs exa£tly125 parts when 100 of reguline copper havebeen ufed, and therefore is precifely fimilar tothe black oxyd left by boiling any cupreousfolution with potafli, fo often mentioned. Thefame chemift gives the following proportions ofthe fub-nitrat.
Black oxyd of copper 67Nitric acid . 16
Water . . 17
100.
The blue or perfeft nitrat on the other hand-contains only 27 per cent, of the black oxyd.
The nitrat of copper is very foluble in alcohol.This fait burns with a remarkably fine blue-green flame when thrown on burning charcoal.
The decompofition of this nitrat by tin is foviolent and rapid, as in certain circumftances toproduce aftual combnllion. This forms anamufing experiment, firft noticed by Dr. Hig-gins, and is thus performed. Spread out a pieceof tin-foil the fize of half a Iheet of paper, layon the middle a fmall heap of the folid bluenitrat, a little moiftened, and over it a few fila-ments of tow, then double up the tin-foil roundit on all fides, twilling it as tight as may bewithout breaking. In a very fhort time it willfeel burning hot, fmall bubbles of the blueliquor will be feen oozing through the foil, and
foon a copious flream of nitrous gas will fhootout from the different openings, attended withminute flalhes of light and deflagration. Alittle fprinkling of water will aflift the effect.
A fine blue pigment is prepared from nitratof copper, called Verditer (Cendres Blues Fr.>)It is made in quantity, chiefly, if not entirely,by the refiners, who, after the procefs of fepa-rating gold from filver by aqua-fortis, recovertire filver from its folution by means of copper,and thus leave a refidue of nitrat of copper.This folution decompofed by lime, the particularmode of which is kept a fecret, made up intocakes, and dried gently, forms the bell kind ofverditer. The refearch made into the nature ofthis valuable pigment by Pelletier, 11 is intereflingin a chemical point of view.
The analyfis of this pigment gave the follow-ing particulars: it was totally foluble in nitricand muriatic acids with much effervefcence ofcarbonic acid: when diflilled without addition,600 grains loft 200 grains, and gave 2 (French )pints of gas almoft totally carbonic acid, toge-ther with a fmall portion of water. The lofs on10a grains is therefore 33-j-, of which the authorof the experiment reckons 30 grains to be car-bonic acid, and the remaining 37 to be water.The calcined refidue was a black fubftance,which was fufed with a reducing flux, left a but-ton of pure copper, and (making feme allowancefor the lofs by this mode, of reduction) was efti-mated to amount to 50 per cent, of the originalverditer. By the feparate treatment of anothefportion by fulphuric acid, fulphat of lime wasproduced, the earth of which amounted to 7grains from roo of the verditer. Confequently-there remains 9§- to compleat the 100, which is"eftimated to be oxygen. Pelletier thereforegives the following rel'ult from his analyfis.
grains
Carbonic acid .30.
Water . 3-3-
Lime . 7
Copper . 50
9 ° 7
Remains for oxygen 9 -§•
100.
It is obvious however that there mull be agreat error in this dlimation in the very fmallquantity of water allowed, fince it is Ihewn by"Prouft, and'fmce by other chemifts, that in allthe blue, or green.ialts of copper, a large quart-’
* Mejuoires, tom. a.