288 Mr. J. Higgin on the Colouring Mattel's of Madder. 



experiments on the pure substance with various oxidizing 

 agents failed totally to produce any alizarine, I am induced to 

 consider it the result of fermentation produced by a peculiar 

 azotized matter found in madder, and to be similar to the re- 

 action between starch and diastase, where the starch becomes 

 first dextrine and afterwards sugar. 



This action becomesvery probable from various experiments, 

 in which it is found that the madder changes are best pro- 

 duced under circumstances favourable to the ordinary action 

 of ferments, and are stopped by such substances as destroy 

 their action. 



I have, in the proximate analysis before-mentioned, used 

 boiling water to extract the principles, as by this means all ulte- 

 rior action is stopped, and the colouring matters are obtained 

 in the same proportion in which they existed in the madder; 

 were cold water used, and the solution allowed to stand a 

 certain time, very little if any xanthine would be obtained, 

 and more than the due proportion of alizarine and rubiacine. 

 , If boiling water be added to madder, the mixture may be 

 allowed to stand any length of time without losing its deep 

 yellow colour and bitter taste. When madder is washed with 

 cold water and the clear filtered solution brought to boil, 

 it becomes turbid, froths up, and is found to be full of small 

 flocculent particles, which when filtered and washed burn with 

 a smell like burning feathers. Boiled with caustic alkali, 

 - they evolve abundance of ammonia; the filtrate from them 

 undergoes no change on standing. 



When to a cold solution of madder any acid or any acid 



salt is added, a flocculent precipitate falls, which is composed 



i of alizarine and rubiacine, pectine and the azotized principle, 



whilst the xanthine remains in solution, and never changes on 



t*Mb*»£< standing. 



If to a very strong solution of madder, made in the cold, 

 alcohol be added in sufficient quantity, a gelatinous substance 

 separates, which is partly pectine and partly the nitrogenous 

 matter; if this be filtered out, the liquor never changes; but 

 if left in, and the liquor gently heated to drive off alcohol, as 

 the flocks redissolve, the changes take place as usual. 



My endeavours to obtain the pure nitrogenous substance, 

 and prove its power of exciting a change in xanthine and ru- 

 biacine, have not yet met with success. I have not been able 

 to obtain it in a soluble, and consequently active condition. 

 My experiments are still in progress, and I give them as far 

 as I can. I made madder into a paste with cold water, ex- 

 pressed strongly, and then added a considerable quantity of 

 alcohol, which threw down a flocculent substance ; 1 washed 



