136 On Madder, and 



madder ; but, that on the other hand, a great loss of colour- 

 ing matter is experienced. The uniformity of the results 

 of these experiments proves the error of the observation, that 

 " by washing madder, clearer colours are produced." Even 

 alizari, which of all the species of madder, gives up to 

 water the greatest quantity of foreign matter, does not 

 afford a clearer red after washing. It may be remarked, 

 that madder, in the large way, should be washed with per- 

 fectly pure water, as water containing chalk renders a 

 quantity of colouring matter effete. 



2. Addition of chalk in dyeing. — The above-mentioned 

 action of chalk upon the red of madder-red, demonstrates 

 the advantage of this addition, which, by the new experi- 

 ments of Schlumberger,* has received additional confirma- 

 tion, that species of madder, which, by themselves give an 

 easily deteriorating red, as Alsace madder, are thereby 

 rendered durable. 



3. Addition of clay in dyeing. — This is fully treated of in 

 Runge's " Farbenchemie." 



ON THE SEPARATION OF THE CONSTITUENTS OF MADDER ON A 

 LARGE SCALE. 



The object of employing, in dyeing, the constituents of 

 madder, instead of madder itself, is threefold, viz. to form 

 a more beautiful, more certain, and a cheaper dye. A more 

 beautiful and more certain effect is undoubtedly produced, 

 when the three colouring matters are employed separately 

 in their purest state, according to the method detailed ; 

 additions may be made to the colouring matters, as chalk 

 and clay, to madder-red, and the choice of the mordants 

 regulated, as the properties of the colouring matter render 

 it necessary ; as, for example, alum mordant with madder- 

 purple forms purple-red ; iron mordant forms lilac violet; 

 and copper mordant with madder-orange produces orange. 

 Runge has endeavoured to hit upon a method of separating 

 these three colouring matters, so as to render them avail- 

 able to the manufacturer ; but he has not succeeded in being 

 able to render the price of the product proportionate to the 

 price of the madder. The separation of the madder-purple 

 from madder-red, especially, is accompanied with great diffi- 



* Records of General Science, i. 208. 



