400 ORGANIC CHEMISTRY. 



described as a mordant, and then immersing it in an 

 acidified solution of prussiate of potash. Prussian blue 

 is thus precipitated in the cloth. This blue is found to 

 be brightened by passing it through a solution of sugar 

 of lead. 



1003. MINERAL GREEN. A mineral green 



How is a min- .*-.., 



eraigreenpro- is produced in the same manner by the em- 

 duced? ployment of sesquichloride of chromium, 



and subsequent immersion in potassa. The color con- 

 sists of sesquioxide of chromium, precipitated from the 

 chromium salt by the action of the alkali. The so- 

 lution of sesquioxide of chromium is prepared by the 

 addition of sugar to a solution of bichromate of potassa 

 in dilute sulphuric acid. A part of the oxygen of the 

 chromic acid being abstracted by the organic matter, it 

 is converted into an oxide, which remains in solution. 



1004. CHROME YELLOW. To produce a 



How is a min- . . 



eral yellow mineral yellow, the cloth may be impreg- 

 produced? nated with acetate or nitrate of lead, then 

 dried and passed through sulphate of soda, to fix the 

 lead as sulphate in the cloth. On finally immersing 

 it in bichromate of potassa, the cloth becomes dyed 

 with yellow chromate of lead. The above process 

 modified by printing instead of saturating with acetate 

 of lead, gives yellow figures on a white ground. 



CALICO PRINTING. 



How is a white 1005. WHITE FIGURES. If it is desired 

 ^oods ro dyed t0 obtain a desi g n in white, on goods dyed 

 duced? with either of the above madder colors, 



