Prof. TyndalPs Contributions to Molecular Physics. 523 



Wishing to examine the radiation from a flame whose product 

 of combustion is sulphurous acid, through sulphurous acid, I 

 resorted to the flame of bisulphide of carbon. Here, however, 

 we had carbonic acid mixed with the sulphurous acid of the flame. 

 Of the heat radiated by this composite source, the absorption 

 by an atmosphere of sulphurous acid amounted to 

 60 per cent. 



The gas was sent from its generating retort through drying- 

 tubes of sulphuric acid into a glass experimental tube 2*8 feet 

 long. The comparative shortness of the tube, and the mixed 

 character of the radiation, rendered the absorption less than it 

 would have been had a source of pure sulphurous acid and a tube 

 as long as that used in the other experiments been employed. 



I subsequently caused the radiation from the carbonic-oxide 

 flame to pass through a few of our vapours, with the following 

 results : — 



Table XXXV. — Radiation through Vapours (tension 0*5 inch) 



Source, carbonic-oxide flame. 





Name of vapour. Deflection. 



Absorption. 



o 



Bisulphide of carbon . 5-5 



9-8 



Chloroform .... 6-0 



10-7 



Formic ether .... 14*5 



25-8 



Sulphuric ether . . . 18*0 



32-1 



Total heat . ; . . 43*0 



100-0 



The same vapours were employed to test the radiation from 

 the hydrogen-flame, with the following results : — 



Table XXXVI. — Radiation through Vapours (tension 0*5 inch). 

 Source, hydrogen-flame. 



Name of vapour. 



Deflection. 



Absorption. 



Bisulphide of carbon 



o 



8-8 



11-9 



Chloroform . . . 



9-9 



13-4 



Sulphuric ether . 



32-0 



42-2 



Formic ether 



35-0 



49-3 



Total heat . . . 



. 48-5 



100-0 



We here find that, in the case of every one of the four vapours, 

 the synchronism with hot aqueous vapour is greater than with 

 hot carbonic acid. The temperature of the hydrogen-flame is 

 higher than that of the carbonic oxide ; but the radiation from the 

 more intense source is most copiously absorbed. It has been 

 already proved that, for waves of slow period, formic ether is 

 more absorbent than sulphuric ether ; while for waves of rapid 



2M 2 



