Dyeing a purple with murexid.

Scientific American 26, 24.12.1859

The objections which lately have been raised as to the instability of the murexid dyes are said to be avoided by the process recently communicated by Mr. Wart; of Leipsig to the Deutsche Muster-Zeitung. According to him, the pieces or woolen stuffs are very carefully cleaned in a strong soda-bath, end then in a soap-liquor. This complete cleansing is indispensable in order to obtain a fine hue. The soda solution should not, of course, be no strong as to effect the animal fiber; though both the soda and soap-liquor should be as concentrated as practicable. When the pieces have been thoroughly rinsed and and drained, they are placed in the following dye-bath:
— To 12 lbs. of wool, add 350 lbs. of lukewarm water, (100° Fahr.) ¼ lb. murexid in powder, and 51 lbs. niter of lead. The murexid being mixed and dissolved in part of the water, the rest of this is added. Then the niter of lead previously dissolved in 30 to 35 lbs. of boiling water is poured in, and lastly the wool added. The dye-bath, is allowed to cool, the wool remaining in it for about 20 hours, after which it is taken out, slightly trashed, and placed into the following fixing and reviving bath: 400 lbs. of cold water, 1 lb. of corrosive sublimate, and 3 lbs. of acetate of soda. Here it remains from five to seven hours, according as a more or less blue tinge is desired. After one dyeing a new operation may be commenced with the same liquors by adding ¾ of the some quantum of dyestuffs. The color thus obtained is stated to be far superior to that with cochineal. The quality and purity of the murexid is of great importance in this process, but the method, according to the opinion of practical men, is the best in use.

We have in former volumes given some practical information on murexid colors, part of which was obtained from German dyers in this city, and part was translated from German publications. Thus far, murexid colors have not superseded those obtained from cochineal, and we think they never will, unless some substitute is discovered for the use of corrosive sublimate, which seems to be required for "raising the bloom," because colors so produced are liable to fade rapidly when exposed to the rays of the sun. We present the above in order to afford a subject for further experiment in practical chemistry.