374 The Art of Dyeing. 



are not destitute of lustre, and earthy as is frequently the 

 case when it is employed as a mordant before dyeing. They 

 retain their lustre much more ; but no pulverulent oxide 

 of copper collects on the surface. 



Therefore, the copper mordant, No. 2, requires no mor- 

 dant to be added to it. 



The copper mordant exhibits here also remarkable pro- 

 perty. It makes the colours light and prove permanent to 

 soap. The logwood blue formed with copper mordant, 

 No. 2, remains after 60 hours exposure to the sun at Berlin, 

 in June, completely blue, while the violet blue at the same 

 time changes to a dirty brown red. 



The mode of using the copper mordant is here the same 

 as above described, except that in order to render it per- 

 manent the cloth should be well moistened before it is 

 placed in the mordant, otherwise spots will be formed. 



ACTION OF SALTS OF TIN UPON CALICO IMPREGNATED WITH 

 ALUM MORDANT. 



If calico impregnated with acetate of alumina mordant. 

 No. 1, and well rinsed, be passed through a solution of 1 

 part salt of tin in 200 water, allowing it to remain as short 

 a time as possible, and washing it afterwards in water, we 

 obtain, after dyeing 9 parts cloth with 12 madder and 36 

 bran, the usual madder-red of such a lustre as cannot be 

 obtained in any other way. But the dye only succeeds on 

 a small scale. It is an important point that the calico shall 

 remain for as short a period as possible in contact with the 

 salt of tin. If it remains longer, the acid of the salt of tin 

 dissolves the alumina, and the madder-red will be much 

 deteriorated. This cannot be avoided on a large scale. 

 Diluting the solution of tin with water does not remedy 

 this defect, as it is accompanied with the precipitation of 

 oxide of tin, and consequently with an acidification of the 

 solution. Alkaline solutions of tin do not succeed better. 

 A solution of salt of tin in caustic lye is not at all practi- 

 cable, as it dissolv.es the alumina, and takes it away so 

 completely from the calico that on dyeing with madder a 

 madder- red is not produced, but only an indistinct pink. 

 The solution of salt of tin in ammonia does not act upon 

 the alumina of the calico, but it has no advantageous action 



