552 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



has been washed with water, and agitated with lemon-juice, 

 indicates saffron-carmine ; b, reappearance of the red color, 

 though weaker, by this treatment aniline-red ; c, production 

 of a yellowish red, or light yellow color by this treatment 

 cochineal, or Brazil-wood, to be distinguished from each other 

 by dipping a fresh sample in concentrated sulphuric acid, 

 when Brazil-wood will at once give a beautiful cherry-red 

 color, and cochineal a yellowish-orange. 



IV. Geeen. Dyers distinguish three kinds of green: viz., 

 those by mixture of blue and yellow, aniline-green from al- 

 dehyde, and new aniline -green from metl^l-iodide. The 

 greens by mixture of blue and yellow, although passing into 

 disuse, may be met with. The principal ones are : indigo 

 with picric acid, indigo with vegetable yellows, Prussian- 

 blue with picric acid, Prussian-blue with vegetable yellows, 

 aniline with picric acid, and aniline-blue with vegetable yel- 

 lows. The blues form the foundation of these greens, and 

 as a rule are insoluble in alcohol, except aniline-blue, while 

 all the yellows mentioned are soluble in alcohol, so that the 

 acquisition of a green color by the alcohol, with which a 

 sample dyed with a mixed green is treated, indicates at once 

 a mixture of aniline-blue and a yellow, if by a previous test 

 the absence of aniline-green was determined. The following 

 course serves to determine the nature of the green dye-stuff: 

 Heat a sample of the fabric on a water-bath for a few minutes 

 in 95 per cent, alcohol. The alcohol either becomes, 1, yel- 

 low, while the fabric becomes more and more blue; or, 2, 

 green, while the fabric retains its color, though with diminish- 

 ed intensity. In the first case Prussian-blue or indigo may 

 be present ; therefore extract the fabric thoroughly with al- 

 cohol, then wash it well with pure water, and cover it with 

 a solution of chloride of lime, whereby indigo-blue will be 

 decolorized, but Prussian-blue will remain unchanged. The 

 yellow may be determined in the alcoholic solution by the 

 method previously given. In the second case aniline-green 

 from aldehyde, aniline-green from methyl-iodide, or aniline- 

 blue mixed with a yellow, must be considered. To distin- 

 guish between them, boil a sample of the fabric in weak 

 hydrochloric acid, whereby decoloration, or change to yel- 

 lowish, indicates the first of the three ; change to rose or lilac, 

 the second ; and change to blue, while the yellow dissolves, 





