322 Dt\ J. W. Capstick. On the Ratio of the [Feb. 14, 



and the residue was dissolved in boiling 1 glacial acetic acid ; the 

 solution on standing deposited small crystalline grains, the ethereal 

 solution of which showed the absorption spectrum of acetylphyl- 

 lotaonin. Another portion of the residue left on evaporation of the 

 ethereal solution was dissolved in boiling alcoholic potash ; the solution, 

 after filtration and addition of water, was acidified with acetic acid 

 and then shaken up with ether; an ethereal solution was obtained 

 showing the characteristic absorption spectrum of phyllotaonin. 



The experiments just described proving the convertibility of 

 phylloxanthin into phyllocyanin, tend to support the view held by 

 some observers that only one chlorophyll really exists, and that there 

 are not two or more chlorophylls as has sometimes been maintained. 

 Under the action of acids, chlorophyll yields phylloxanthin, which is 

 then converted into phyllocyanin. The latter when treated with 

 alkalis gives phyllotaonin, and this, by the more energetic action of 

 alkalis at a higher temperature, yields phylloporphyrin. The pro- 

 gressive increase in the number of absorption bands in passing 

 through this series, and the gradual shifting of the bands from the 

 red to the blue end of the spectrum, are points worthy of notice. 



III. " On the Ratio of the Specific Heats of some Compound 

 Gases." By J. W. CAPSTICK, D.Sc., M.A., Fellow of Trinity 

 College, Cambridge. Communicated by Professor J. J. 

 THOMSON, F.R.S. Received January 25, 1895. 



(Abstract.) 



The experiments described are a continuation of those of which an 

 account was given in the ' Philosophical Transactions,' vol. 185, p. 1. 



The apparatus and method of procedure were the same as were 

 described in the former paper. Kundt's dust-figure method was used 

 for finding the velocity of sound in the gas, and the ratio of the 

 specific heats was calculated by means of the formula 



7 = 1'408 X p X (jj 

 \* 



the last factor being added to the ordinary formula in order to 

 correct for the deviation of the gas from Boyle's law. 



The densities and isothermal curves were determined experi- 

 mentally. 



The results are as follows : 



