In order to obtain a temperature co-efficient, the measurements 

 summarized in Table II. were carried out at deg. 



Table II, 



The value of the constant increases 2^25 times for 10 deg., a normal 

 figure. 



B. Derivatives of phthalic acid, {k for phthalic anhydride = 

 0^00461.) 



3. Dtchlorphthalic Anhydride. — It was expected that this 

 anhydride would be at about the limit of the measur- 

 able, and it was necessary therefore that it should be 

 obtained pure. Commercial acid was thrice crystallised 

 6117. n 



