I9I2] George D. Beal and George A. Geiger 85 



III. ATTEMPTS TO SEPARATE PIGMENTS BY DIALYSIS 



The outcome of Test 25 encouraged us to ascertain whether 

 two dissimilar pigments like scarlet R and malachite green might be 

 wholly separated from each other by dialysis thru rubber in a suit- 

 able solvent, e. g., ethyl acetate (see tests 40 and 45). A mixture 

 of the two pigments dissolved in ethyl acetate was accordingly sub- 

 jected to the usual mechanical treatment, but the diffusate was re- 

 peatedly replaced with fresh solvent. The results are indicated in 

 the f ollowing summary : 

 Continuous differential diffusion of scarlet R and malachite green. 



March 28 — ist diffusate ii-i p.m. Bright red. 



March 28 — 2nd diffusate 4 p.m. Bright red. 



March 28 — 3rd diffusate 11 p.m. Deep red. 



March 29 — 4ith diffusate 12.30 a.m. Deep purplish red. 



March 29 — 5th diffusate i a.m. Light purplish red. 



March 29 — 6th diffusate 10.45 ^■^- Deep red with decidedly 

 bluish tinge. 



March 29 — 7th diffusate 12.30 p.m. Light blue. 



March 29 — 8th diffusate 9.15 p.m. Blue green. 



March 30 — 9th diffusate 11.50 a.m. Blue green. 



March 31 — loth diffusate 9.15 a.m. Blue green. 



April I — iith diffusate i p.m. Blue green. 



April 2 — I2th diffusate 11.50 p.m. Light green. 



April 3 — I3th diffusate 11.50 p.m. Light green. 



Altho scarlet R and malachite green showed widely different 

 rates of diffusion when they were treated separately, the results 

 detailed above made it evident that it would be difficult if not im- 

 possible to obtain all the scarlet R from mixtures like the one em- 

 ployed without removing some of the malachite green with the red 

 pigment. 



By subjecting Solutions of scarlet R and malachite green of simi- 

 lar concentrations independently to diffusion in the usual way, we 

 duplicated the blue and green effects with malachite green and the 

 red effects with scarlet R, but the purplish colorations could not he 

 ohtained under such circumstances. That these purplish effects 

 were due to early diffusion of the malachite green with scarlet 

 R, and that the red pigment facilitated the passage of the green one, 

 are clearly indicated by the results. 



