284 The Art of Dyeing. 



forms with the sulphuric acid glauber salt or sulphate of 

 soda, which does not separate, but remains in solution. 



This circumstance often impedes the manufacturer, and 

 renders it impossible to employ a strong acetate of alumina 

 mordant of alum and acetate of soda, as such a mordant 

 does not thicken well with starch. The glauber salt con- 

 tained in it destroys the pasty nature of the mordant and 

 makes it watery. On this account a pattern printed with 

 it will not preserve a regular edge. 



Acetate of soda is, however, very useful for the prepara- 

 tion of mordants which are not thickened with starch, but 

 with gum or tragacanth, as for example, with acetate of tin 

 formed of tin salt and acetate of soda. 



As the salt of tin is a muriatic acid salt, it is improper 

 to employ sugar of lead for the purpose of converting it 

 into an acetate, as the tin mordant will by that means be 

 rendered impure by the presence of muriate of lead which 

 affects the purity of the colour. 



By the use of acetate of soda, on the other hand, common 

 salt is produced, which has no injurious action on the dyes. 



Acetate of lime or pyrolignate of lime now occurs in 

 commerce for the purpose of being employed instead of 

 sugar of lead. When a solution of it is mixed with one of 

 alum, gypsum precipitates, and the supernatant liquor is 

 acetate of alumina. This contains still much gypsum dis- 

 solved in it, and it cannot, therefore, be employed for many 

 colours, as for example, madder-red. 



Salt of tin as employed in chemical manufactures occurs 

 in yellowish white crystals, which form a clear solution 

 with a small quantity of water, but with much water give 

 a milkiness which settles into a white precipitate. 



Salt of tin consists of muriatic acid and tin, and produces, 

 when printed upon cotton in a strong solution, injurious 

 effects if allowed to remain in contact with it for any length 

 of time. As, however, salt of tin, employed as a discharger, 

 quickly produces its action, the cotton may be washed after 

 the printing, and the injurious effects prevented. 



Salt of tin is an important ingredient for yellow and red 

 block-colours. It is better to employ, in this case, acetate 

 of tin, which may be formed by double decomposition with 

 acetate of soda and muriate of tin. For this purpose, we 



