VERDITER, BLUE 1073 



Each cluster of crystals weighs from five to six pounds ; and, in general, their total 

 weight is equal to about oue-third of the verdigris employed. 



VERDINE. One of the aniline colours, prepared by M. Eusebi. 



VERDITER, or Bremen Green. This pigment is a light powder, having a blue 

 or bluish-green colour. The first is most esteemed. When -worked up with oil or 

 glue, it resists the air very well. 



The following is, according to M. J. G. Gentele, the process of fabrication in Bremen, 

 Cassel, Eisenach, Minden, &c. : 225 Ibs. of sea salt, and 222 Ibs. of blue vitriol, both 

 free from iron, are mixed in the dry state, and then reduced between mill-stones with 

 water to a thick homogeneous paste. 225 Ibs. of plates of old copper are cut by 

 scissors into bits of an inch square, then thrown and agitated in a wooden tub con- 

 taining 2 Ibs. of sulphuric acid, diluted with a sufficient quantity of water, for the 

 purpose of separating the impurities ; they are afterwards washed with pure water 

 in casks made to revolve upon their axes. The bits of copper being placed in oxidation- 

 chests, along with the magma of common salt and blue vitriol previously prepared in 

 strata of half an inch thick, they are left for some time to their mutual reaction. The 

 above chests are made of oaken planks joined without iron nails, and set aside in a 

 cellar, or other place of moderate temperature. The saline mixture, which is partially 

 converted into sulphate of soda and chloride of copper, absorbs oxygen from the air, 

 whereby the metallic copper passes into a hydrated oxide, with a rapidity propor- 

 tioned to the extent of the surfaces exposed to the atmosphere. During the three 

 months that the process requires, the whole mass must be turned over once every 

 week, with a copper shovel, transferring it into an empty chest alongside, and then 

 back into the former one. At the end of three months the corroded copper scales 

 must be picked out, and the saline particles separated from the slimy oxide with the 

 help of as little water as possible. This oxidised Schalmm or mud is filtered, then 

 thrown by means of a bucket containing 30 Ibs., in a tub, where it is carefully 

 divided or comminuted. For every six pailfuls of schaimm thus thrown into the large 

 tub, 12 Ibs. of muriatic acid, at 15 Beaume, are to be added; the mixture is to 

 be stirred, and then left at rest for twenty-four or thirty-six hours. Into another 

 tub, called the ' blue black,' there is to be introduced, in like manner, for every six 

 pailfuls of the acidified schaimm, fifteen similar pailfuls of a solution of colourless 

 clear caustic alkali, at 19 Beaume. When the back has remained long enough at 

 rest, there is to be poured into it a pailful of pure water for every pailful of schaimm. 

 When all is thus prepared, the set of workmen who are to empty the back, and 

 those who are to stir, must be placed alongside of each. The first set transfer the 

 schaimm rapidly into the latter back, where the second set mix and agitate it all the 

 time requisite to convert the mass into a consistent state, and then leave it at rest 

 from thirty-six to forty-eight hours. The whole mass is to be now washed ; with 

 which view it is to be stirred about with the affusion of water, allowed to settle, and 

 the supernatant liquor is drawn off. This process is to be repeated till no more traces 

 of potash remain among the blue. The deposit must be then thrown upon a filter, 

 where it is to be kept moist, and exposed freely to the air. The pigment is now 

 squeezed in the filter-bags, cut into bits, and dried in the atmosphere, or at a tem- 

 perature not exceeding 78 Fahr. It is only after the most complete desiccation that 

 the colour acquires its greatest lustre. 



VSRDITER, BXiUE. This is a precipitate of oxide of copper with lime, made 

 by adding that earth, in its purest state, to the solution of nitrate of copper, obtained 

 in quantities by the refiners, in parting gold and silver from copper by nitric acid. 

 The cupreous precipitate must be triturated with lime, after it is nearly dry, to bring 

 out the fine velvety blue colour. The process is delicate. 



The Cendres bltucs en pate of the French, though analogous, are in some respects a 

 different preparation. To make it, dissolve sulphate of copper in hot water, in such 

 proportions that the liquid may have a density of 1-3. Take 240 pound measures of 

 this solution, and divide it equally into four open-headed casks ; add to each of these 

 45 pound measures of a boiling-hot solution of muriate of lime, of spec. grav. 

 1 - 317, whereby a double decomposition will ensue, with the formation of muriate of 

 copper and sulphate of lime, which precipitates. It is of consequence to work the 

 materials well together at the moment of mixture, to prevent the precipitate agglome- 

 rating in unequal masses. After leaving it to settle for 12 hours, a small quantity of 

 the clear liquor may be examined, to see whether the just proportions of the two salts 

 have been employed, which is done by adding either sulphate of copper or muriate of 

 lime. Should either cause much precipitation, some of the other must be poured in 

 till the equivalent decomposition be accomplished ; though less harm results from an 

 excess of sulphate of copper than of muriate of lime. 



The muriate of copper is to be decanted from the subsided gypsum, which must 

 be drained and washed in a filter; and these blue liquors are to be added to the 



VOL, III. 3 Z 



