Iron Mordants. 67 



by vinegar. Air and soap-suds produce scarcely any effect. 

 Boiling in solution of 300 lbs. water and 2 lbs. soap does 

 not deteriorate the colour ; the shades become bluer and 

 clearer than before. 



VIOLET BLUE FROM LOGWOOD AND ALUM MORDANT. 



For bright colours, the alum mordant, No. 3, is used, or 

 the alum solution mixed with soda in the manner described. 

 The dark violet blue should be produced with alum mor- 

 dant. No. 2. It is necessary to allow the mordanted cloth 

 to hang up some days before the dyeing takes place. The 

 mordanted cloth is cleared in running water. 



In order that the colour may not pass into black, bran 

 should be added to the solution. The bran is first boiled 

 with logwood and a little water ; then more water is added, 

 and the heat increased and raised to boiling. 



For 10 lbs. of mordanted cloth, 2 lbs. logwood and 2 lbs. 

 bran are required to produce a dark logwood blue. Hot 

 soap-suds heightens the colour, and makes it more perma- 

 nent to acids. 



Properties. — Towards light, air and soap-suds, logwood 

 blue shews much permanence. 



Potash makes brown spots which are removed by vinegar. 



Ammonia does not change the dye, but dissolves a por- 

 tion, and makes it paler. 



Lime water effects no alteration. 



Lime juice makes bright red spots which ammonia com- 

 pletely dissolves. 



Tin mordant i No. 1, printed upon it forms a lilac. 



Tin mordant, No. 2, printed on it discharges a clear 

 violet. 



Chloride of lime discharges a yellow like nankeen. 



IRON MORDANTS. 



Next to the alum mordants, iron mordants are of most 

 importance to the dyer. Their affinity for the cotton fibre 

 is, if possible, stronger than that of the alum mordants. 

 The iron mordants bear the same relation to dark colours 

 that the alum mordants do to light ones. 



For this purpose, sulphuric and acetic acid mordants are 

 employed. 



