1835.] Madder DyeAn^. 46^ 



Tin mordant is formed in the same way as the iron mor- 

 dant, by means of a solution of 1 part salt of tin in 50 parts 

 of pure water. 



Lead mordant, with a solution of sugar of lead, 1 part 

 sugar of lead in 30 parts of water. The cloth should be 

 rinsed after impregnation. It takes up, in these circum- 

 stances, a sufficient quantity of oxide of lead. 



Copper mordant is formed by a similar proceeding with 

 ammoniuret of copper. By dipping and washing the cloth 

 in this solution, the cotton fibre absorbs as much oxide of 

 copper as is sufficient to produce the requisite dark colour. 



Testing the Colour. The cotton which has received the 

 mordant may be submitted, in the hands of the chemist, to 

 a double test, so that its qualities may be determined both 

 qualitatively and quantitatively. The peculiar shades which 

 the colouring matter produces, in combination with the 

 cotton, may be termed the goodness, and the degree, or 

 the depth of shade, the value of the colour. By proper 

 treatment, both of these properties, as well as the peculia- 

 rities of the cloth, may be determined by one process. 



A small quantity of the colouring matter is weighed out, 

 and heated with pure water, in a porcelain dish, over a 

 sprit-of-wine flame ; equal portions of the cotton, impreg- 

 nated with the mordants, are placed in it, and coloured in 

 succession, the solution being gradually raised to the boiling 

 point. When the first portion of cotton appears to absorb 

 no more colour, it should be removed, rinsed in a little 

 water, and its absorption again urged. The same trials are 

 to be made with the second, third, and fourth portions, 

 until that point is attained where the absorption of colour- 

 ing matter terminates, and where, consequently, the cotton 

 receives no additional colour. 



After being dried, the pieces of cotton which have been 

 equally saturated, are to be weighed, and the power of the 

 cloth to receive colour ascertained. In this way, I have 

 ascertained the saturating power of the three madder pig- 

 ments treated of in the subsequent part of this paper. When 

 a colouring substance contains a mixture of several colour- 

 ing matters, by this successive dyeing, a partial separation 

 can be produced. We obtain, at the beginning and end of 

 the process, quite different shades, (Runges Farhenchemie, 

 174 J. As in this case, and in many others, the first portions 



