Violet from Madder and Iron. 447 



combining intimately with the unmordanted calico fibre, 

 and imparting to it a distinct colour ; therefore, we do not 

 obtain white grounds by dyeing white grounds with madder, 

 logwood, uutgalls, yellow wood, quercitron, &c, but must 

 have recourse to other means, as bleached grass, soap, 

 bran and chloride of soda. 



Relation of the cotton, combined with the colouring matter, 

 to mordants. When calico is boiled with nutgalls, it ac- 

 quires a yellowish colour, which, by being dipped in a so- 

 lution of iron alum, is turned into a dark gray. When 

 boiled a second time, in the nutgall solution, it becomes 

 still darker. Bablah and madder produce similar results. 



This mode of dyeing differs from the common method in 

 this respect, that the dye is applied twice, and the mor- 

 dant only once ; viz., the cloth is first dyed, then mor- 

 danted, and then again dyed. In this way we obtain, with- 

 out much trouble and loss of time, very equal grounds ; 

 and we have it in our power, by repeating the dyeing and 

 mordanting, to produce a variety of shades. 



The properties of cloth dyed with nutgalls and iron alum, 

 are similar to those of nutgall gray. The different colours 

 produced from these materials, by modifying their applica- 

 tion, are remarkable. When the mordant is employed last, 

 as in nutgall gray, a combination is formed with excess of 

 mordant ; if the proceeding is reversed, a combination is 

 produced with excess of gallic acid. The former approaches 

 blue, the latter red. 



Gray, from bablah and iron alum. The cloth is dipped in 

 a solution of iron alum (1 iron alum to 60 water), pressed 

 and then washed. To make the colour clearer, the cloth 

 may be previously boiled for a quarter of an hour, in an 

 infusion of bablah. The dying is performed at the boiling 

 temperature. To form the first colour, 10 lbs. of cloth are 

 employed, with 1 lb. bablah. To produce the second, the 

 quantity of bablah should be triple. 



Tan acts in the same way as bablah, and gives similar 

 shades. But what is very remarkable, oak bark, willow 

 bark, and persian berries, employed in the same way, make 

 no difference. Specimens dyed twice are not darker than 

 those dyed once. 



Violet from madder mid iron alum. — The cloth is dipped in 



