Madder Dyeing. 45 



liquid, from which a vapour proceeds, which does not collect 

 in the form of needles, but as a brown-red, viscid, mass on the 

 sides of the glass. By the addition of more heat it may be 

 driven along the tube, but is then covered with carbonaceous 

 matter; so that the sublimed madder-purple cannot be again 

 sublimed without decomposition. It colours alum, and 

 iron mordanted cotton, as well as madder-purple ; and its 

 solution in caustic potash presents a cherry-red colour. 

 In completely pure water, madder-purple forms, with the 

 addition of heat, a dark, pink-coloured solution. In cold 

 water it is little soluble. A hot solution, when cooled, de- 

 posits no flocks. Acids change the pink solution to a yel- 

 low colour. 



In well-water, or water containing lime, the madder- 

 purple dissolves at first ; but a portion combines with the 

 whole lime, and precipitates in the form of a dark-red gum. 

 The colours to be produced by madder-purple must be com- 

 municated by means of water, perfectly free from lime, else 

 the loss of colouring matter will be very great. 



Spirit, alcohol, and ether, dissolve madder-purple very 

 readily, and form orange-yellow solutions. After the 

 evaporation of the liquid, the madder-purple remains, in 

 the form of a bright, orange-yellow, crystalline powder. 

 When water is added to a hot, concentrated solution of 

 madder-purple, in spirit, a quantity of silky crystals is sepa- 

 rated, which swim in the solution. 



Dilute acids, at the boiling temperature, dissolve madder- 

 purple, forming a yellow solution ; on cooling, it separates 

 in the form of orange-yellow flocks. 



Ammonia forms, with madder-purple, a beautiful bright- 

 red solution, which, when printed upon unmordanted cotton, 

 and, after drying, being washed in hot water, leaves a clear 

 pink colour. When printed upon cotton with alum mor- 

 dant, and washed in boiling water, a clear red is obtained. 



Solution of potash dissolves madder-purple, forming a 

 fine cherry red-coloured solution, and gives, upon unmor- 

 danted cotton, after clearing with hot water, a pink colour. 

 On mordanted cotton a saturated dark-red colour is ob- 

 tained in the same circumstances. 



The solution of madder-purple, in spirit, imparts to un- 

 mordanted cotton a pink colour, which is reddened by 



