PERKIN'S VIOLET , OR MAUVE.

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colour, named Regina purple. The following is a full description of hisprocess:—“ I take red dye, such as is made from aniline or its homologues,and, without the admixture of either aniline or its homologue, I heat it carefully,in a suitable apparatus, to a temperature by preference between 390° and 420° F.The substance quickly assumes the appearance of a dark semi-solid mass, thered dye being transformed into a dark substance with evolution of ammonia.The mass I prefer afterwards to extract with acetic acid, using a quantity ofacid about equal in weight to the amount of the red dye treated, and this acidI dilute with enough alcohol to make a dye of convenient commercialstrength: the solution obtained is of a deep violet or purple colour, and maybe used direCtly for dyeing purposes. What I claim is the producing a violetor purple colour from red dye, such as is made from aniline or its homologues,by carefully treating it as described, without admixture either of aniline or itshomologue.” M. Stark patented a method of producing this colour, by boilingfor two or three hours a mixture of a salt of aniline with red prussiate ofpotassa, leaving the whole to cool, when a greyish-blue precipitate settles atthe bottom. It is, however, not certain whether the colour thus obtained cancompete with those already used. The use of the red prussiate of potassa forproducing aniline purple had been mentioned by M. Emile Kopp before thedate of M. Stark’s patent.

The paste violet (mauve) is tested for its tinctorial value in the followingmanner:—3 grms. are exactly weighed, and dissolved in 50 c.c. of acetic acid.To this solution is added a quantity of 100 grms. of gum-water (containing500 grms. of gum to the litre), and next a quantity of 100 grms. of albumen-water (containing 500 grms. of albumen to the litre). This mixture is usedto print, by means of the roller, stripes on muslin. After the printing the stuffis dried, steamed, washed, and compared with a standard sample. This assaycan also be executed by a dyeing process in the following manner:—2 grms.of the paste are dissolved in 10 c.c. of alcohol (or methylated spirits), and'diluted with water so as to yield a quantity of 1 litre ; 50 c.c. of this liquidare taken, and diluted to a | litre. This fluid is brought to ebullition, and init 5 grms. of wool are dyed, so as to exhaust the bath. The purples abovementioned, when fixed on woven tissues, are recognised by the followingreactions, it being remembered that these colours can only be perhaps confusedwith the rosaniline violet and French purple (a peculiar orchil colour—to theformer the Regina violet , just spoken of, belongs):—(1). When’aCted upon withstrong mineral acids (sulphuric or hydrochloric) the dye in question turns blue.(2). Caustic alkalies do not aCt upon it in the cold. (3). A solution of sul-phurous acid in water into which a piece of sheet zinc is placed causes theimmediate decolouration of any tissue thus dyed.

A series of aniline violets, sold under a number of fanciful names, are ob-tained from rosaniline by the process of phenylation ,—that is, one or two atomsof the hydrogen present in the rosaniline are replaced by the same numberof equivalents of phenyl or of tolyl. The conversion of the red into a violetis effected in an enamelled iron retort, holding about 20 litres, heated in aparaffin bath. The head is joined to the body by means of pressure-screws.The head is made high to promote the re-condensation of the aniline, whichis volatilised. The retort is fitted with a mechanical stirrer, in the axis ofwhich lies a tube through which steam can pass. The mixtures used vary in