i86 



BIO-CHEMICAL JOURNAL 



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FIG. 3 



In another experiment, in which the proportion of paper to dye 

 was greater than in the previous one, equilibrium was reached in six 

 minutes. So that the rate of change is proportional in the first place 

 to the concentration of the adsorbing body. I have not enough data, 

 however, to warrant any further discussion of this point. The reaction 

 is one taking place in a heterogeneous system and its mathematical 

 expression a complex one. It is probable that diffusion plays a con- 

 siderable part as indicated by the results of the next experiment, 

 which was made to obtain some idea of the temperature coefficient of 

 the reaction-velocity. It was found that, for some reason or other - 

 perhaps some action of the platinized electrodes on the dye at low 

 temperatures the electrical conductivity method did not give satisfac- 

 tory results, so that the colorimetric method, though more laborious 

 and less sensitive, was made use of. 



Experiment: 50 c.c. of 0^005 P er ccnt - congo-red in 5 per cent, 

 alcohol in each of two flasks, a circle of filter-paper added to each, and 



