DYEING AND CALICO PRINTING.

186

Magenta.

hi

water and to dye with the strained decodtion a known weight of fine whitewoollen yarn or cloth. By thus comparing different samples, their respedlivetindtorial power can be readily ascertained, and the presence of tarry matters,unconverted aniline, &c., may be detedted by the flatness and brownish castof the colour. Sugar is sometimes used as an adulterant. This may bedetedted by treating the sample with concentrated alcohol. The magentadissolves and is filtered off, whilst the sugar remains behind undissolved.

The following method is used to ascertain whether a magenta is a pure saltof rosaniline or is contaminated with mauvaniline, violaniline, chrysotoluidine,&c. The colour is dissolved in as little alcohol as possible, the solutiondiluted with its own bulk of water or rather more, and a drop is taken up by

Ponceau.