Elements of the art of dyeing ... / by M. Berthollet ; Translated from the French by William Hamilton.

  • Claude Louis Berthollet
Date:
1791
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Licence: Public Domain Mark

Credit: Elements of the art of dyeing ... / by M. Berthollet ; Translated from the French by William Hamilton. Source: Wellcome Collection.

    311/368 (page 253)
    ART OF DYEING. infufion of galls may be employée], which will give a black tinge to a folution of the aluni, if tlicrc be iron in it. Secondly, Does it contain much alkali in the form of fui pliât ? The method employed by Mr. Dé- croizille may be recurred to for the purpofe of afeertaining this, taking true roman alum for the fubjefl of comparifon. Thirty parts of water at the common tem- pérature, are required to diffolve one of alum, accoiding to Bergman, and of boiling water three parts are fufficient. Alum is decompofed not only by alkalis, out e\ en by the carbonats of lime and mag- ncfia : yet it is to be obferved, that even alkalis take away only a part of the acid, the precipitate retaining nearly half of it, ' and being a fait with a deficiency of acid, as Mr. Baume lias fliewn. If this piecipitate be diffolved in an acid, as the nitric acid or muriatic, this acid feizes the excefs of alumine, and re-effablifhes the propoitions which conflitute alum : fo that by évaporation we obtain cryffals, which appear diflerent Irom thofe of aluni, but, on a careful examination, their form appears referable to one of the varieties of the cryffals of that fait. This I hâve afcertained on cryffals procurcd U 2 from