Madder Dyeing. 53 



solution, which changes by the access of light into orange. 

 When printed upon cotton impregnated with alum-mordant 

 the result is not superior to that with the ammoniacal 

 solution ; 30 parts of mordanted cloth require for saturation 

 only 1 part of madder-orange. It requires, therefore, the 

 greatest quantity for saturation of all the madder dyes ; 

 madder-purple requiring only 16 and madder-red 22 of cloth 

 for saturation. Madder-orange affords a clear combina- 

 tion with cotton when it is quite pure. Hence, the addition 

 of clay and chalk is injurious. When a certain quantity 

 of clay is added with the cloth, the colour is brighter, 

 but when the quantity is increased the colour becomes 

 reddish orange. 



The remarkable action of the clay now points out the 

 reason of its efficacy in dyeing with madder. With madder- 

 red, clay strongly reddens its yellowish-red combination with 

 alumina. Here the clay is the cause of the alteration, and 

 while added in proper proportion, it prevents the direct 

 brightening of madder-orange. The reason is that the clay 

 has more affinity for the madder-orange than the alu- 

 minous mordanted cotton : If we examine the clay em- 

 ployed, we find that it has usually a bright orange-colour, 

 and becomes, by digestion in caustic potash, as red as the 

 madder-orange itself. In like manner, the dye solution 

 employed is reddened by potash. The colouring matter is, 

 therefore, disguised (zuruckgehalten) by both. But, since 

 madder-orange gives a shade of yellow to the red colour of 

 the madder-purple and madder-red, it is evident that the 

 presence of clay makes the colour more red. 



The addition of chalk produces the same effect as with 

 madder purple : If 1 orange, 30 cloth, and 1 chalk, are 

 used, the colour will not be half so dark as without chalk. 

 Much gum is thereby separated. The colour thus produced 

 is more rapidly deteriorated by light than one which is 

 formed without, chalk. 



With copper mordant, an orange colour is formed. Cot- 

 ton impregnated with the lead mordant, acquires a reddish 

 rust colour, and iron mordanted cotton is coloured strongly 

 nut-brown. With tin- tin mordant upon cotton a bright 

 yellow- naitldn is obtained. Wecan readily distinguish in the 

 last dye, whether the madder-orange is free from madder- 



