The Art of Dyeing. 371 



and lime are analos^ous in composition, although they were 

 prepared in quite different ways, this resin would appear to 

 form only one set of saliform compounds with hases, and 

 in this set the oxygen in the resin is four times as great as 

 that in the base. It appears to follow from this, that the 

 atomic weight of the resin is four times as great as it is made 

 by the formula given above. The right formula, for the 

 composition of the resin, is, therefore, not 10 C -f- 16 H + 

 O, but 40 C + 64 H + 4 O. It appears to me to be con- 

 venient, and, probably, also correct, to express the last 

 formula as follows, 4 (10 C + 16 H) + 4 O. 

 ( To he continued.) 



Article X. 



The Art of Dyeing. 



{Continued from page 208.) 



This mode of mordanting is very suitable for the pro- 

 duction of a saturated logwood blue, which is more per- 

 manent than logwood violet ; as logwood colours contain- 

 ing copper are far more permanent than those containing 

 simple alum mordants. 



BROWN AND BLUE FROM ALUM MORDANTS, AND COPPER MOR- 

 DANTS, WITH WILLOW BARK AND LOGWOOD. 



1. Brown from Alum and Copper Mordants and Willow 

 Bark. — The process of mordanting cotton for willow bark 

 brown has been already given. The colour is darker in 

 proportion to the length of time that the calico remains in 

 the copper mordant. The bark of the basket,^ or also the 

 crack -f- willow should be first boiled in a little water; then 

 the proper quantity is added, and the dyeing performed 

 without allowing the solution to boil completely. 



By boiling with soap-suds the dye loses its powdery 

 appearance, and becomes still darker. 



PROPERTIES OF WILLOW-BROWN. 



Light and air, as well as washing with soap, produce no 

 considerable change upon this colour. 



* Salix viminalis. — Edit. t Salix/?-agi7is. — Edit. 



2 B 2 



