COAL-TAR 61 



that are now made from coal-tar were formerly ex-* 

 tracted from plants. 



Indigo, for instance, has been prepared from the most 

 ancient time out of the juice of a plant grown in India. 

 The preparation of the dye was a toilsome process. The 

 natives cut the plant by hand, squatting on the ground, 

 and then beat it up in vats with paddles, standing up to 

 their waists in the blue liquid. In 1896 there were 

 more than a million and a half acres devoted to its 

 culture in that country. Shortly after that the Ger- 

 mans invented a way of making artificial indigo 

 no, let us say more correctly, of making indigo artifi- 

 cially from coal-tar, and then the land and natives of 

 India were released for better employment. Since the 

 war America makes her own indigo and has enough 

 surplus to export. In 1920 there was produced in the 

 United States more than 18,000,000 pounds of indigo, 

 which is more than twice what we imported before the 

 war. 



Next to indigo the most popular of the old vegetable 

 dyes was madder. This has been used for more than 

 two thousand years. It is the ground root of an Asian 

 plant and is known as "Turkey Red." Extensive 

 fields were given over to its culture in France and the 

 Netherlands until 1869 when two German chemists, 

 Graebe and Liebermann, discovered how to make the 

 pure dyestuff, alizarin, from a waste product of coal- 

 tar, anthracene. The artificial alizarin is better and 

 cheaper, and this early triumph of synthetic chemistry 

 was, at the end of the first decade of its manufacture, 

 saving the world $20,000,000 a year, and is now saving 



