Madder Dyeing. 47 



loses some of its lustre, and becomes brighter, while the 

 soapy water is coloured red. The same effect is produced 

 on the bright dye. 



Carbonate of soda, in the proportion of 1 part soda to 

 8 cloth and 240 water, acts advantageously when boiled for 

 a quarter of an hour. With the dark colour the solution 

 becomes slightly red, but on the bright colour no effect is 

 produced. The shades are not perceptibly changed. Clay 

 has no injurious effect upon either colour. If we take 

 1 part cloth, 3 clay, and 240 water, and boil for a quarter 

 of an hour, the clay removes no colour, and the solution, 

 at the utmost, is only slightly tinged red. The shades 

 are not perceptibly altered. From these results, it is obvi- 

 ous that the combination of madder-purple with alumina 

 forms the common madder-purple, or Turkey-red ; and that 

 it also enters, as the principal constituent, into common 

 madder- red. Soap, soda, and clay, rather tend to render 

 the colour clearer. Light, also, after the action of a July 

 sun for 60 hours, makes it brighter. 



Madder-red. — The discrimination of madder-red, and its 

 separation from madder-purple, depend upon its insolubility 

 in a strong alum solution. When madder has been washed 

 according to the process recommended forseparatingmadder- 

 purple, if it be then boiled with alum solution, a brown-red 

 precipitate separates, containing much madder- red. From 

 the precipitate it may be separated by boiling the latter fre- 

 quently with strong muriatic acid, washing it well, and 

 treating it with boiling spirit of wine. This gives a dark- 

 brownish red coloured tincture, which, after the evaporation 

 of the acid, and cooling, deposits an orange-yellow precipi- 

 tate. When washed with cold spirit it consists of madder- 

 red, which is mixed with much madder-purple. The latter 

 is separated by boiling it with a solution of alum, which is 

 to be repeated as long as the liquid is coloured red. When 

 both colouring matters have a resinous consistence, the 

 action of the alum must be diminished, previously dissolving 

 them in a little spirit, and then adding the alum solution. 

 When the point is attained at which the alum solution re- 

 mains colourless, and no more madder-purple is left, the 

 yellow precipitate is to be edulcorated, dried, and dissolved 

 In ether. The ethereal solution being evaporated, the 



