358 VEGETABLE SUBSTANCES. 



ported in large quantities into England, and ob- 

 tain a proportionate higher price than the prepared 

 madder. 



In 1804 the gold medal of the Society for the En- 

 couragement of Arts, &c. was voted to Sir H. C. 

 Englefield, for his discovery of a pigment prepared 

 from madder. He obtained a fine lake by many dif- 

 ferent processes, and found that the colour produced 

 from the Smyrna was of a deeper and richer tint 

 than any prepared from the Dutch madder. In 

 pursuing his experiments he discovered that the co- 

 louring matter might be extracted from fresh madder, 

 and thus not only all the expenses and difficulty 

 attendant on the process for prepared madder might 

 be avoided, but the cost of carriage would be one- 

 fourth less than for the roots ; while separated from 

 these the colouring matter might be kept for any 

 length of time without danger of being spoiled. A 

 further advantage would also arise in the quantity 

 obtained, as all the colouring matter could be ex- 

 tracted ; while in the manner which the dyers use 

 the roots, a very considerable part of the colour is 

 left in the refuse matter, and consequently wasted. 



The following is a slight sketch of the method 

 proposed for obtaining this extract. A given quan- 

 tity of the roots ground into a pulp is put into a 

 woollen bag. This is then triturated in large vats 

 filled with a certain relative proportion of water ; 

 the friction is continued until the colouring matter is 

 entirely washed out of the madder ; the water thus 

 loaded with colour is boiled, an iron vessel must 

 not be used, as a chemical change would take place 

 and the colour would be spoiled. After being boiled 

 it is poured into an earthen receiver, and a solution 

 of alum is mixed with it in given quantities. Then 

 a certain proportion of a saturated solution of mild 

 vegetable alkali is added, which causes effervescence, 



