﻿528 Mr. F. Burden on the Boiling-points of Organic Bodies. 



into the interior will be very approximately by a conical point ; 

 so that in the impossibility of operating experimentally on mere 

 rays the phenomena will not be sensibly different from what 

 they would have been had the transition been made rigorously 

 by a conical point." 



Between the theory here advanced and that of Fresnel obser- 

 vation ought to decide; but it does not appear that any experi- 

 ments hitherto made are competent to do so. As Professor 

 Stokes points out, all the measurements which are to be com- 

 bined in one calculation should refer to the same specimen of the 

 crystal ; otherwise an element of uncertainty is introduced suffi- 

 cient to render the application of the test ambiguous. Should 

 the verdict go against the view of the present paper, it is hard 

 to see how any consistent theory is possible^ which shall embrace 

 at once the laws of scattering, regular reflection, and double 

 refraction. 



LXVI. Boiling-points of Organic Bodies. 

 By F. Burden, Esq .* 



SINCE it was observed that the boiling-points of each homo- 

 logous series of organic bodies was higher for every addition 

 to the substance of CH 2 , several continental chemists (but espe- 

 cially M. Kopp) have tried to discover the law which connects 

 the boiling-point with the composition. No proportionate rela- 

 tion has yet been found to connect different series; and yet I 

 believe I can show that the greater number of those organic 

 bodies which contain only carbon, hydrogen, and oxygen obey a 

 law of great generality and simplicity, and that there are reasons 

 for believing that further experiments will reduce the number of 

 exceptions. 



It has been calculated by Joule and Clausius, on the hypo- 

 thesis of a motion of translation in gaseous molecules, that the 

 velocity of the atoms of hydrogen necessary to balance a pres- 

 sure of 15 lbs. per square inch at the temperature of 0° C. is 

 6050 feet per second. And it has been assumed by them, on 

 mechanical grounds, and verified experimentally by Graham, that 

 the product of the specific gravity of any gas upon the square of 

 the velocity is a constant, under the same circumstances of tem- 

 perature and pressure. As the specific gravity of hydrogen is 

 taken as unity, this constant must be 36,602,500. The velocity 

 of the molecules of any vapour at 0° C. can therefore be obtained 

 by dividing this constant by the specific gravity and extracting 

 the square root. In this way was calculated the fourth column 

 of the accompanying Tables. 



It has been further deduced from known laws that this velocity 

 * Communicated by the Author. 



