CONTRIBUTIONS TO MOLECULAR PHYSICS 417 



with the shorter waves is greater than that of the formic. 

 Hence we may infer that the atoms of formic ether oscil- 

 late, on the whole, more slowly than those of sulphuric 

 ether. 



When the source of heat is a Leslie*s cube coated with 

 lampblack and filled with boiling water, the opacity of 

 formic ether in comparison with sulphuric is very de- 

 cided. With this source also the positions of chloroform 

 and iodide of methyl are inverted. For a white-hot spiral, 

 the absorption of chloroform vapor being 10 per cent, 

 that of iodide of methyl is 16; with the blackened cube 

 as source, the absorption by chloroform is 22 per cent, 

 while that by the iodide of methyl is only 19. This in- 

 version is not the result of temperature merely; for when 

 a platinum wire, heated to the temperature of boiling 

 water, is employed as a source, the iodide continues to 

 be the most powerful absorber. All the experiments 

 hitherto made go to prove that from heated lampblack an 

 emission takes place which synchronizes in an especial 

 manner with chloroform. For the cube at 100° C, coated 

 with lampblack, the absorption by chloroform is more 

 than three times that by bisulphide of carbon; for the 

 radiation from the most luminous portion of a gas-flame 

 the absorption by chloroform is also considerably in ex- 

 cess of that by bisulphide of carbon; while, for the flame 

 of a Bunsen's burner, from which the incandescent carbon 

 particles are removed by the free admixture of air, the 

 absorption by bisulphide of carbon is nearly twice that by 

 chloroform. The removal of the carbon particles more than 

 doubles the relative transparency of the chloroform. Test- 

 ing, moreover, the radiation from various parts of the 

 same flame, it was found that for the blue base of the 



