2561. Test for Sugar in Aniline Dyes

2561. Test for Sugar in Aniline Dyes. Aniline blue and aniline green have been found adulterated with a considerable quantity of sugar. Mr. Joly, of Brussels, has also found this to be the case with red aniline colors, such as fuchsine, rubine, etc., the adulteration amounting in some cases to as much as 50 per cent. The amount of sugar present can be ascertained by treating a sample of the suspected dye with absolute alcohol; or, still better, with a mixture of alcohol and ether; the sugar will remain undissolved.

2562. To Remove Sugar from Aniline Dyes

2562. To Remove Sugar from Aniline Dyes. If it be found by the test given in No. 2561, that an aniline color has been adulterated with sugar, this may be removed by repeatedly washing the color with cold water, which will dissolve the sugar.

2563. General Directions for the Use of Aniline Dyes

2563.     General Directions for the Use of Aniline Dyes. It is impossible to use any dye, successfully, without due regard to cleanliness. This is, perhaps, more particularly the case with the anilines. The slightest trace of a foreign substance will often materially alter the shade. Earthen or enameled vessels should be used whenever practicable. Iron is generally to be avoided, if for no other reason than that it is difficult to say when it is really clean. "Woolen and silken goods, before being dyed, should be thoroughly washed in soap and water, and then carefully rinsed in clean rain water. Cotton requires a previous mordanting before it can be dyed with anilines, as vegetable fibre possesses no affinity for the colors. The preparation generally consists in treatment by sumac, or stannate of soda, and subsequently by sulphuric acid; special directions will be given in those cases requiring particular treatment. Old fabrics which were dyed before, may be freed from color by previous boiling for an hour in strong soapsuds. The spirit used should be pure, and especially free from aldehyde ; methyl spirit does not appear to injure some of the dyes: Spirit containing shellac turns roseine of a bluish color.

2564. To Distinguish Aniline from Other Dyes

2564.    To Distinguish Aniline from Other Dyes. Aniline colors, for dyeing purposes, are now used to such an extent throughout the country as almost to exclude all others, on account of their brilliancy and cheapness. They are, however, liable to lose in appearance by bright sunlight, and in lustre by the artificial light of gas or candles. It is, therefore, desirable to have a ready means by which they can be recognized. This is all the more necessary, as arsenic acid is generally employed in their preparation; and a cloth that has been dyed with an aniline color containing it may have absorbed a considerable quantity of that dangerous article. The readiest way for its detection is to boil the flannel, or whatever other cloth it may be, with a solution of caustic soda or potassa, and, after filtering the fluid from the residue, neutralizing it with hydrochloric acid. If the cloth has been dyed with an aniline color, the fluid will show a coloration. Most of the aniline dyes may also be extracted by boiling alcohol, which process, perhaps, can be performed in less time than the other.