MADDER. 133 



gray is obtained by passing the goods thus mordanted through 

 a solution of sulphuret of calcium ; and a deep-black by the 

 same, finishing with iron mordant and campeachy wood. 

 (Technologiste, 1846.) 



Neiv Mordant. — Broquette's new method of fixing colors, 

 or his new mordant, is a solution of casein in ammonia, with 

 which the goods are impregnated, and then heated to expel 

 the ammonia and leave the casein on the cloth. He has also 

 employed casein with lime alone, or with lime and ammonia. 

 See Chem. Gaz. viii. 884. 



4. Dye-stuffs. — Many experiments have been recently made 

 on well-known dye-stuffs, especially on the invaluable madder, 

 and a few new dyes have been added to the list ; but experience 

 alone can prove their durability, beauty, and economy. 



Madder. — The investigation of this valuable coloring-sub- 

 stance is attended with many difiiculties, in consequence of 

 the presence of several different coloring principles, which 

 have some analogy in color, are different in their properties, 

 and yet, according to some observations, one may be trans- 

 formed into another. It is probable that the substances ali- 

 zarin and xatithin, found some twenty-five years since, were 

 not pure. In 1885, Runge described, in a valuable essay on 

 madder, five coloring principles in it, madder-purple, red, 

 orange, yelloiv, and brown, and mentioned also two acids, ruhi- 

 acic and maddric ; but he viewed the sesubstances solely as a 

 dyer and not as a chemist, leaving the most important part un- 

 done, their more important combinations, transformations, and 

 their composition. 



Schiel also examined the colors of madder. (See essay in 

 Ann. d. Chem. u. Pharm. Oct. 1846.) To prepare madde.r- 

 purple, water is poured over the ground madder in a wooden 

 vat, suffered to stand for 1 or 2 days, and drawn off. The 

 madder is then pressed, boiled in a copper vessel with a strong 

 solution of alum, and filtered hot. It deposits a reddish-brown 

 substance, which is separated by filtration. Sulphuric acid is 

 added to the red solution, which deposits the purple in 24 

 hours. The latter is again dissolved in alum and precipitated. 

 M 



