46 On Madder, and 



alkalies. Cotton impregnated with the alum mordant pro- 

 duces, at a boiling temperature, a different colour according 

 to the quantity of purple added : 



One part purple to 16 cloth affords a dark reddish-brown 

 ,, ,, 40 ,, a saturated purple-red 



,, ,, 80 ,, a saturated bright-red. 



Clay, when added to the liquid, modifies these colours, and 

 makes them brighter, and more of a scarlet shade, in con- 

 sequence of the loss of colouring matter by the formation 

 of a red gummy matter. When 240 parts clay are employed 

 with 1 purple and 40 cloth, the shade is only half as dark 

 as when no clay is used. 



The presence of chalk is decidedly injurious. When one 

 part of madder-purple is boiled with one part chalk, in a 

 great quantity of water, no precipitate is formed, but a 

 bright-red solution is produced. Presently a red gummy 

 matter is deposited on the sides of the vessel. If the quan- 

 tity of chalk is gradually increased, a point is attained where 

 all the madder purple separates from the chalk, and is con- 

 verted into red gum. The liquid has now lost its power of 

 dyeing. The presence of chalk, in dyeing with madder, is 

 also prejudicial as with madder-purple. This effect is mo- 

 dified in the case of madder-red, where the chalk combines 

 by preference. 



With cotton which is oiled and mordanted for the recep- 

 tion of the Turkey-red dye, the madder-purple does not 

 produce a true Turkey-red. It possesses too much blue ; 

 and, in order to acquire the first, it must be subjected to 

 the usual clearing operations. Without this it is very light. 



With tin, lead, and iron mordants, the madder-purple 

 produces colours which pass from red, through brown-red 

 and brown, into blue. The colour with tin mordant is 

 pink; with lead mordant, scarlet; with copper mordant, 

 red-brown ; and lastly, with iron mordant, violet. All these 

 colours receive thei" full impress by the employment of a 

 sufficiently strong mordant. 



By soap, carbonate of soda, and clay, neither the dark 

 nor the bright red of the madder-purple is changed. 

 Still, soap produces an injurious effect when an excess is 

 employed. If the dark dye is boiled for a quarter of an 

 hour with 1 part of soap, 3 cloth, and 240 water, the dye 



