28 THE ROYAL SOCIETY OF CANADA 



preliminary inquiry into the matter, it was necessary to determine 

 whether quantitative relations really existed between the dye and the 

 emulsoid. The following experiment was designed to do this. 



To each of seven vials containing each 5 cc. of Opuntia mucilage 

 of the same kind as used above, 5 cc. of neutral red were added in a 

 series of concentrations beginning with the highest, viz. 50 mg. in 

 10 cc. of water, in each member of the series the dye being reduced in 

 concentration by one-half. The lowest concentration was, therefore, 

 that of 1-5 mg. in 10 cc. water. The absolute amounts of the dye 

 available to each quantum of mucilage was 25 mg. and 0-75 mg. for 

 the extremes of the series. The dye solution was floated gently onto 

 and remained supernatant on the mucilage. 



There soon appeared a dark zone at the tension surface between 

 the two, which developed a thickness roughly proportional to the 

 concentration of the dye. This dark zone was obvious evidence of 

 flocculation. 



Eighteen hours later the mucilage in contact with the lower con- 

 centrations of the dye had increased in volume, while that in contact 

 with the higher concentrations had decreased.^ Twelve hours later 

 still, the relative volumes with one exception had remained too little 

 changed for measurement, but five days later considerable changes 

 in the original dimensions had occurred. In the highest dye concen- 

 tration the mucilage had shrunk to. a rounded clot lying on the bottom 

 of the vial. The accompanying table shows the gains and losses in 

 percentages of the original total volume of which the mucilage and 

 dye solution each occupied 50 per cent. Number five did not fit into 

 the series very well, but it must be admitted that the measurement 

 offered a certain amount of difficulty. The general trend of the 

 figures is, however, unmistakable. Ultimately {i.e., at the end of a 

 five-day period), in Nos. 6 and 7 a continuous firm clot was formed, 

 while the supernatant fluid was limpid and optically empty (no 

 Tyndall effect or suspensoids). In all the others (1 to 5 incl.) the fluid 

 was turbid (especially on shaking) and accordingly a pronounced 

 Tyndall effect appeared. When examined ultramicroscopically it 

 was found that No. 1 showed a few suspensoids, their numbers being 

 increased progressively in the series with the concentration of the dye. 

 No flocks were present in No. 1, but small ones occurred in No. 2 and 

 more and larger ones progressively in the series. At the same time, 



^ This may indicate osmotic relations, the flocculation zone serving as a semi- 

 permeable membrane. I have observed that when Congo red is allowed to diffuse 

 into gelatine, a dense adsorption zone is formed, after which the rate of diffusion, 

 through this zone is of necessity very much lowered and at length is reduced to zero. 



