1835.] 



Calico- Printing. 



327 



solution is precipitating the oxide of lead on those parts of 

 the cloth to which the paste had been applied. After being 

 washed in water, the cloth is passed through a solution of 

 bichromate of potash. Those parts only become yellow 

 upon which the oxide of lead has been fixed. But the 

 colour is at first pale and dirty, from the presence of a 

 quantity of oxide of copper deposited at the same time with 

 the oxide of lead. To remove the copper and heighten the 

 yellow, the cloth is immersed in a weak solution of muriatic 

 acid in water. 



9. Orange and Yellow upon Blue. 



The process in this case is the same as in the last, only 

 the cloth, instead of being passed through a hot solution 

 of bichromate of potash, is passed through dichromate of 

 potash. Two atoms of oxide of lead combine with one 

 atom of chromic acid and thus produce the orange. When 

 weak nitric acid thickened with gum is printed upon 

 portions of this orange, half of the oxide of lead is removed, 

 and the orange is immediately converted into yellow. 



10. Chrome Yellow upon Bronze. 



* /v. 



