[llovd] precipitation OF DYES 27 



Vesuvin, Congo red, neutral red and methylene blue, on the other 

 hand, had a marked effect. As seen in the previous experiment, there 

 occurred a great increase in turbidity, less rapidly consummated in the 

 vesuvin mixture than in the others. Nor did the change proceed with 

 equal rates in the two mucilages. The Congo-red-Linum mucilage 

 mixture assumed the character of a jelly in an hour or so, and in 24 

 hours a shrunken clot had formed, floating in a perfectly limpid solution 

 of the dye. The Opuntia mixture showed no rapid change, but was 

 quite turbid in 24 hours. Exactly the reverse was true of neutral red, 

 which formed a clot with Opuntia mucilage and a turbid mixture with 

 that of Linum. Methylene blue produced a turbid mixture in both 

 cases. 



Vesuvin in the course of six days lowered the viscidity of the 

 mucilage so that it became watery, and this was equally true of both 

 Linum and Opuntia. With Linum mucilage Congo red had formed a 

 curdy mass or clot on the bottom of the vial; with Opuntia mucilage, 

 a dense curdy clot, three-fourths the total volume. This curd adhered 

 to the sides of the vial above the fluid like the curdy casein in butter- 

 milk. The viscosity of the mixture appeared rather higher than that 

 of the control. 



Neutral red formed a curd with both Linum and Opuntia mucilage, 

 the viscosity of the supernatant fluid being approximately that of 

 water. The viscosity of the methylene blue preparations was in both 

 instances near to that of water. 



Eighteen days later the viscosity of the control had been materi- 

 ally lowered, and this, as the odour attested, was due to the activity 

 of organisms. That of the methyl orange, eosin and fuchsin was but 

 slightly lowered, albeit these preparations were not entirely free of 

 organisms, this being true of both mucilages. Secondary changes 

 which had also taken place in the remaining preparations, referable I 

 have no doubt to the activity of organisms as evidenced by odours, 

 prevent attaching weight to the changes observed. Only to the re- 

 tention of viscidity in the presence of the dyes mentioned above is 

 attention directed, as further evidence of the non-effect of these dyes 

 on the physical properties of the mucilages. 



It was evident from the foregoing experiment that both Linum 

 and Opuntia mucilage are affected in the same way but in different 

 degrees by certain dyes and not by others. Either coagulation or 

 flocculation occurs, according to the quantitative conditions or char- 

 acter of the dyes, the coagulum being more continuous in the Opuntia 

 mucilage than in that of Linum, doubtless because of the lower state 

 of dispersal in the preparation of the latter. To integrate an avowedly 



