Ahm in combination with Copper Mordants. 207 



the calico, while it crystallizes and is deposited in greater 

 quantities on some places than on others. The greater 

 proportion is also carried away by washing. It is, there- 

 fore, necessary to proceed in a different mode. The calico 

 impregnated with acetate of alumina should be treated with 

 copper mordant. Here a reraarkableproperty is exhibited. 



The calico saturated with the acetate of alumina after 

 hanging for 6 or 8 days, and being well washed in running 

 water, when brought into the copper mordant. No. 2, and 

 allowed to remain there for a quarter of an hour, takes up 

 such a quantity of oxide of copper that the colour becomes 

 as dark as Prussian blue. 



A piece of unmordan ted calico of equal size when treated 

 in the same manner, takes up only so much of the copper 

 mordant as to acquire a blueish shade. 



A considerable affinity thus appears to exist between the 

 alumina and copper, which increases in proportion to the 

 smallness in quantity of ammonia which the copper mordant 

 contains. In the last case, so much oxide of copper is 

 collected upon the calico that it lies upon it as a powder, 

 by which the lustre is deteriorated. 



The proper proportion of the ammonia to the copper is 

 10 lbs. solution of ammonia to 200 lbs. copper mordant. 

 No. 2. The calico impregnated with the acetate of alumina 

 should be treated with this mixture in the manner described. 



Only a limited number of colouring matters answer for 

 this kind of mordanting, while such as contain much tan, 

 as nut-galls, tannin, (fee, give powdery colours. Other 

 dyes, as Persian berries, separate oxide of copper from the 

 calico and form a yellowish-brown colour in the solution. 

 Notwithstanding this, however, when 5 lbs. of cloth are 

 employed for 1 lb. of berries, a saturated yellow-brown is 

 formed. 



The action of the madder solution is most remarkable 

 upon cloth mordanted in this way. If we take two loths 

 (1 oz.) of calico impregnated with the acetate of alumina 

 mordant, divide it into two equal parts, leave the one 

 portion as it is, and treat the other portion with the copper 

 mordant as already described, and dye both in a solution 

 of madder ; the 2 loths thus take up so much as to become 

 dark. The calico impregnated with the acetate of alumina 

 mordant alone becomes a bright orange, while that im- 



