RESEARCHES ON THE VOLATILE HYDROCARBONS. 157 
of the new facts which I am about to present. Schréder,* not satisfied with Kopp’s 
explanation of the discrepancies between the observed and theoretical boiling-points, 
on the ground of errors of determination of the former, argues that the influence of 
C,H, on boiling-points is variable in different series according to the peculiar nature 
of the C, H, in each case. He regards organic compounds for the most part made up 
of radicals, which he calls “components,” of which he makes seven. Three of these 
are composed of carbon and hydrogen, viz. : — 
Formyl = (C, H,) — (“C, H,”) — which is supposed to raise the boiling-point of a 
substance 52° C. 
Methylen = (C, H,)" — “(C, H,)"” — which is supposed to raise the boiling-point 
of a body 21°. 
Elayl = (C,H,)* — “(C, H,)*” — which is supposed te raise the boiling-point 17°. 
Subsequently (Pogg. Ann., 64, 101) the latter number was changed by Schréder to 16°. 
A fourth component was made up of a double atom of hydrogen, (H,) — “(Hz)” —, 
which was supposed to lower the boiling-point 3°; but this also was afterwards 
changed to 10° (Pogg. Ann., 64, 372). (The other three components, having no 
direct bearing on the hydrocarbons, are omitted.) By means of these components 
Schréder (Pogg. Ann., 62, 188) proposed to calculate the boiling-points of different 
substances in the following manner. Having estimated the sum of the influence of 
the different components of a body, the number 70 was in all cases to be deducted. 
Subsequently Schréder+ was led to substitute, in these calculations, the influence of 
the separate elements for that of the components. Each double atom of carbon (C;) 
was estimated to raise the boiling-point of a compound 31°; and each double atom of 
hydrogen (H,) to lower it 10°. As in the former case, the number 70 was to be 
deducted from the sum of the influences of the different elements contained in the 
compound, to give the true boiling-point. Example: calculation of the boiling-point 
of benzole, Cy, H,; Cy == 6C,; 31° x 6= 186°; H,=3H,; —10° x 3=— 30°; 
186° — 30° — 70° = 86° = the calculated boiling-point of benzole by this method ; 
which agrees exactly with the latest determination at the date of Schréder’s memoir. 
Léwig t estimates the influence of the elementary atoms on the boiling-point dif 
ferently from Schréder ; and obtains numbers such that, to find.the boiling-point of a 
compound it is only required to add together the numbers corresponding to the 
* Poggendorff’s Annalen, 1844, LXII. 184, 337. 
+ Poggendorff’s Annalen, 1845, LXIV. 367; 1846, LXVIL 40. 
{ Poggendorff’s Annalen, 1845, LXTIV. 250. 
