c o c
C 0 c
( 311 )
water was decompofed by acids, which diflolvedthe cobalt leaving the fulphur. The fulphuradheres fo ftrohgly to the cobalt by the inter-mede of the alkali, that heat will not feparatethem. This fulphuret is much more fufiblethan cobalt itfelf.
None of the alloys of cobalt deferve particularnotice. This metal does not unite, or only invery fmall proportion, with bifmuth, filver andmercury. With gold, platina, copper, tin, iron,nickel, antimony and arfenic it unites eafily andin various proportions. With lead, accordingto Gmelin, cobalt may be alloyed when wrap-ped up in fheet lead and covered with charcoal.
All proportions of cobalt not exceeding equalweights with the lead make an uniform alloy,brittle and hard in proportion to the quantity ofcobalt.
When lead or bifmuth are cupelled withcobalt, the latter is left behind in the form of ablack oxyd.
The foie ufe of cobalt in the arts is for the fineblue which any of its oxyds gives when mixedand melted with any vitrifiable matter. The ex-tent of the colouring power is perhaps more thanthat of any other of the metallic oxyds, for onegrain of the pure oxyd will give a very full blueto half an ounce, or 240 grains of glafs. Theoxyd melted per fe gives fo intenfe a blue as toappear perfectly black, except juft at the thinedges of the fharp fragments when broken.Manganefe greatly impairs the clearnefs of thecolour, giving a ftrong admixture of muddypurple, but this effedt is corredted by addinga little arfeniat of i'oda or other arfenical fait.(For further particulars on this fubjedt fee thearticle Glasses coloured.)
Cobalt is alfo faid to be contained in fmallquantity in fome of the fine Chinefe metallicalloys, but its ufe is very doubtful, and the dear-nefs of the metal would prevent it from beingufed to any extent for fuch purpofes in Europe .
It may be added that in moft of the experi-ments on the alloys and the fulphurets of thismetal, it has been ufed in only its common Hateof purity, that is to fay, ftill alloyed with arfenicand iron, and probably with nickel.
The affinities of cobalt are Hated to be in themoift way as follows: the gallic, oxalic, muri-atic, fulphuric, tartareous, nitric, phofphoric,fluoric, fuccinic, citric, acetic, arfenic, boracic,pruffic and carbonic acids, and ammonia.,
COCCOLITE. a The colour of this mineralis grafs-green palling to olive or blackilh green.It occurs in maffes compofed of fmall granular
diftindt concretions like feeds or minute kernels(whence its name.) Thefe concretions are fome-what angular, and {hew a tendency to cryftal-lization. They have a considerable vitreousluftre. The fracture of the grains is lamellarin two different directions, feemingly at rightangles to each other: the fracture of the mafsis granular. It is tranflucid; fufficiently hardto fcratch glafs, and brittle. Sp.gr. 3.37.
Coccolite is very difficultly fuiible jVr fe beforethe blowpipe. According to an analylis byVauquelin, it confilts of50 Silex,
24 Lime,
10 Magnefia,
7 Oxyd of iron,
3 Ditto of manganefe,
1.5 Alumine.
95-5
4.5 lofs.
100.0
This mineral has been lately difeovered by"Abildgaard, in veins at Arendahl in Norway , atNej-ika in Sweden , and in the iron mines ofHellefta and Afl’ebo in Sudermania. It hasfcarcely yet acquired a permanent ftation infyftems of mineralogy, and will probably beranked as a variety of augite.
COCHINEAL. Coccus CaBi Linn.
The fubftance known in commerce by thename of cochineal, is in the form of hemif-pherical fhrivelled grains, about an eighth ofan inch long, of a deep reddilh purple colour,and covered more or lefs with a white down;they are very light, and eafily rubbed to powderbetween the fingers. The merchants diftin-guifh at leaft two kinds, called grana fina andgratia fylvejlra of- thefe the latter is not morethan half the fize of the former, and coveredwith a much longer down; on which account italways bears a much lower price in the market.
Cochineal was firft introduced into Europe from Mexico about the year 1523, and was forfome time fuppofed to be the berry or feed ofa vegetable. It was at length however afeer--tained that thefe grains were the females of aparticular fpecies of infedt, called by naturahjtsCoccus cadti, and of the fame genus as theKerrnes (Coccus Ilicis Linn.)
The cochineal infedt is a native of Mexico, ,and was in common ufe among the inhabitants,as a dying-drug when the Spaniards firft came.
a Hauy, Brochant.