Bladder Dyeing. 49 



violet-blue solution, which, by an excess of madder-red, 

 passes into purple. For printing it gives no better results 

 than the solution in ammonia. To unmordauted cotton the 

 solution in spirits imparts a yellow rust colour. 



By printing with caustic alkalies, especially barytes, clear 

 lilac colours are obtained, which have no permanence. 



To the aluminous mordanted cotton, madder-red imparts 

 a dark-red colour, without brightness (feuer) and beauty. 



For 28 parts of cloth 1 part madder-red is sufficient for 

 saturation. If more is used the colour is not darker, and 

 the excess remains in the vat. The addition of clay is of 

 decided benefit. It makes the colour considerably darker, 

 and redder. The best proportion is to take |th of the 

 weight of the cloth, or, 132 parts clay, 1 madder-red, and 

 22 cloth. 



The addition of chalk to madder-purple is very injurious, 

 but to madder-red is advantageous. 



If 1 part madder-red, and 1 part chalk, are boiled with a 

 sufficient quantity of water, the solution previously yellow 

 becomes dark purple-red ; and 22 parts of alumed cotton 

 acquire a colour which is brighter than that of the cotton 

 saturated with madder-purple. 



More chalk, as, for example, about as much again, affords 

 also a good result. In general, however, a greater quantity 

 is injurious, as the colour becomes brighter than with 1 part 

 chalk, and the gum which is formed is redder. 



This remarkable action of chalk upon madder-red explains 

 the advantage which is gained by adding chalk in dyeing 

 with certain kinds of madder.* In these it is evident that 

 madder-red is the principal constituent. A remarkable 

 distinction is thus also made between madder-purple and 

 madder-red, viz. That the addition of chalk to the first is 

 prejudicial. It is, therefore, necessary to determine the 

 proportion of madder-red in the species of madder employed. 



Still more remarkable is the action of chalk upon madder- 

 red in dyeing cotton which is oiled and mordanted for the 

 Turkey-red dye. Without the addition of chalk the last 

 acquires a dull, dirty, brown-red colour. With chalk a 

 fine Turkey-red colour is procured, without clearing. When 



* See Scblumberger and Robiquet's Explanation of tlio Ellect of Calcareous 

 Matter on Madder, Records of General Science, i. 9.07. — Edit. 

 VOL. III. E 



