28 UNIVERSITY OF COLORADO STUDIES 



We see that k decreases, indicating as before that the velocity 

 is less rapid at the end than would be expected from Gouldberg and 

 Waag's law. 



If desired, a complete record of the position of the mercury 

 column could be obtained by any of the methods for recording the 

 readings of a mercury thermometer. 



The chief advantages of the above described methods are, first, 

 that the chemical system is not disturbed during the reaction; second, 

 that no time is lost in titration or other chemical tests for the state 

 of the system, thus making it possible to investigate rapid reactions; 

 third, that it is not necessary for the experimenter to make observa- 

 tions during the reaction, which is a tedious piece of work if the 

 velocity is very small; and fourth, the curves are drawn by purely 

 mechanical processes, thus avoiding the influence of the personal 

 equation. 



A third method based upon the change in the index of refraction 

 of the chemical system as measured by the motion of interference 

 bands is being perfected. 



In conclusion I wish to thank my assistant, Mr. F. C. Blake, for 

 the care with which he has helped me obtain the above data. He 

 and his brother, Mr. J. C. Blake, are at work applying the methods 

 to hitherto uninvestigated reactions. 



Hale Physical Laboratory, University of Colorado. 



