[lloyd] 



PRECIPITATION' OF DYES 



29 



the viscidity^" was highest in No. 1 and decreased progressively with 

 the series, till, in Nos. 4 and 5 it was reduced to that of water approxi- 

 mately. In Nos. 6 and 7 the viscosity has increased in the clot, and it 

 will be seen that the original system had separated into two by 

 syr^eresis. An additional feature may here be mentioned tentatively 

 at least, namely, that in Nos. 4 and 5 there appeared a marked green 

 fluorescence, which is absent from neutral red alone. Whether this 

 was a true fluorescence I do not know, but the green colour was 

 evident enough in a strong beam of light playing on the edges of the 

 fluid. 



Depth of Mucilage and of Superposed Zone of Dye Solution After 

 Periods Indicated 



1" The terms viscous and viscid appear to have been used in the literature more 

 or less interchangeably. I am here using viscid to describe the tenacity, or internal 

 pulling power of cactus mucilage, absent from Linum mucilage, which has viscosity. 

 Assuming these to be different properties it should be stated, to avoid confusion, 

 that the dyes which affect the viscidity of cactus mucilage also affect the viscosity 

 of Linum mucilage and the viscosity of Cactus mucilage after the viscidity has 

 disappeared. 



