MADDER. 927 



the first are known as Adrian ople or Turkey reds. The colour- 

 ing principles of madder have an affinity for the earth alumina 

 and peroxides of iron and tin, like other organic colouring 

 matters soluble in water, and form insoluble precipitates with 

 these oxides, which are known as lakes. By impregnating 

 cotton cloth with a solution of acetate of alumina, or with alum 

 of which the acid has been in a great measure neutralised by an 

 alkali, it retains a portion of that earth, (or of either the other 

 metallic oxides mentioned if treated with a solution of their 

 salts), of which it is not deprived by washing ; these oxides 

 having an attraction or affinity for the fibre of the cotton. If 

 the cloth so prepared be introduced into a hot solution of any 

 organic colouring matter, the latter is taken up from the solution 

 and becomes attached to the cloth by combining with its alu- 

 mina, which, thus forms the link that unites the cloth and 

 colouring matter. The alumina is termed the mordant, and 

 such is the ordinary method of fixing colours by means of 

 mordants. Cotton may be dyed with madder by this simple 

 process, but the colour is dull. To produce a fine red the 

 cloth must be submitted to a long preparation occupying some 

 weeks, and consisting of a number of operations, the effect of 

 many of which is very imperfectly understood, but every one of 

 them nevertheless indispensable for a good result. The chief 

 features of this remarkable process, without entering into a 

 detail of the routine operations are (1) the impregnation of the 

 cloth with an imperfect soap and some principles from sheeps' 

 dung. By this treatment, which consists of several operations 

 repeated more than once, the cloth acquires an animal odour, 

 which it retains through the rest of the operations. It is said that 

 when old cotton cloth that has been worn about the person and 

 frequently washed is to be dyed, this process may be omitted 

 altogether. (2) The cloth is afterwards soaked in an infusion 

 of vegetables or of sumach, which gives it a yellow colour and 

 assists also in fixing the madder afterwards, this is the galling, 

 an accessory operation not confined, to madder dyeing. (3) 

 Alumina is fixed in the cloth in the manner previously described. 

 (4) The cloth is then dyed by entering it into a boiler with 

 ground or chopped madder while the water is cold, gradually 

 raising the temperature, and boiling them together for a couple 

 of hours. A certain quantity of bullock's blood is also added 

 to the madder bath. The colour thus fixed is brownish red 



