RESEARCHES ON THE VOLATILE HYI>KOCARB«'\s. 157 



of the new facts which I am about to present. Schi"der* 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 2 H 2 on boiling-points is variable in different series according to the peculiar nature 

 of the C 2 H 2 in each case. He regards organic compounds for the most part made np 

 of radicals, which he calls "components," of which he makes seven. Three of these 

 are composed of carbon and hydrogen, viz. : 



Formyl = (C 4 H 2 ) — (" C 4 H 4 ") — which is supposed to raise the boiling-point of a 



substance 52° C. 



Methylen = (C 2 H 2 ) m — " (C 2 H 4 ) m " — which is supposed to raise the boiling-point 



of a body 21 



Elayl = (C 2 H 2 ) e — «(C 2 H 4 ) e " — which is supposed to raise the boiling-point 17 c 

 Subsequently (Pogg. Ann., 64, 101) the latter number was changed by Schroder to 16°. 



A fourth component was made up of a double atom of hydrogen, (IIJ — "(Hi) 

 which was supposed to lower the boiling-point 3°; but this also was iftei wards 

 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 

 Schroder (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 



y 



o 



the different components of a body, the number 70 was in all cases to be deducted. 

 Subsequently Schroderf was led to substitute, in these calculations, the influence of 

 the separate elements for that of the components. Each double atom of carbon (C 2 ) 

 was estimated to raise the boiling-point of a compound 31°; and each double atom of 

 hydrogen (H 2 ) to lower it 10°. As in the former case, the number 70 vis 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 bo.hng-pomt 

 of benzole, C 12 H 6 ; C 12 =6C 2 ; 31° X 6 = 186* ; H 6 =3IL; _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 Schroder's memoir. 

 Lowig % estimates the influence of the elementary atoms on the bo.hng-point dif- 

 ferently from Schroder ; and obtains numbers such that, to find the bmhng-point of a 

 compound it is only required to add together the numbers corresponding to the 



* 



dorflT 



t Poggendorff's Annalen, 1845, LXIV. 367 ; 1846, LXVH. 

 X Poggendorff's Annalen, 1845, LXIV. 250. 



