On the. Relation between Boiling-point and Composition, 227 
“On the Relation between Boiling-point and Composition in 
Organic Compounds.” By Hermann Kopp. — . 
The author was the first to observe(in 1841) that, on comparing pairs 
of analogous organic compounds, the same difference in boiling-point 
corresponds frequently to the same difference in composition. This 
relation between boiling-point and composition, when first pointed 
out, was repeatedly denied, but is now generally admitted. The con- 
tinued experiments of the author, as well as of numerous other 
inquirers, have since fixed many boiling-points which had hitherto 
remained undetermined, and corrected such as had been inaccu- 
rately observed. In the present paper the author has collected his 
experimental determinations, and has given a survey of all the facts 
satisfactorily established up to the present moment regarding the 
relations between boiling-point and composition. 
The several propositions previously announced by the author 
were :-— 
1. An alcohol, Cx H,,+20., differmg in composition from ethylic 
alcohol (C,H,O,, boiling at 78° C.) by « C,H,, more or less, boils 
2X 19° higher or lower than ethylic alcohol. 
2. The boiling-point of an acid, C,H,0O,, is 40° higher than that 
of the corresponding alcohol, C,,H,+20s. 
3. The boiling-point of a compound ether is 82° higher than th 
boiling-point of the isomeric acid, C,H,Ou.. 
These propositions supply the means of calculating the boiling- 
points of all alcohols, C, Hn+20z ; of all acids, C,H,,O.4; of all com- 
pound ethers, C,H,Ox. The author contrasts the values thus cal- 
culated for these substances with the available results of direct obser- 
vation. The Table embraces eight alcohols, Cx Hn+2Q., nine acids,- 
C,H, O04, and twenty-three compound ethers, C,,H,O.; the calculated 
boiling-points agree, as a general rule, with those obtained by experi- 
ment, as well as two boiling-points of one and the same substance 
determined by different observers. We are thus justified in assuming 
that the calculated boiling-point of other alcohols, acids, and ethers 
belonging to this series will also be found to coincide with the results 
of observation. 
The boiling-points of other monatomic alcohols, Cp H»O2, other 
monatomic acids, C,,H,,O,, and other compound ethers, Cp HmOus 
are closely allied with the series previously discussed. A substance 
containing xC more or less than the analogous term of the previous 
class, in which the same number of oxygen and of hydrogen equiva- 
lents is present, boils x x 14°°5 higher or lower ; or, what amounts to 
the same thing, a difference of #H more or less of hydrogen lowers 
or raises the boiling-pointt by «x5°. Thus benzoic acid, C,,H,O,; 
boils 8 x 14°-5 higher than propionic acid, C,H,O,, or 8 x 5° higher 
than cenanthylic acid, C,,H,,O,; cinnamate of ethyl, C,,H,,O,, boils 
10 x 14°5 higher than butyrate of ethyl, C,,H,,O,, or 10 x 5° higher 
than pelargonate of ethyl, C,,H,,O,. 
The author compares the boiling-points thus calculated for five 
alcohols, C,, HO; for six acids, C, H»O.; and for sixteen compound 
ethers, C,, H,,.O4, with the results of observation. In almost all cases 
the concordance is sufficient. 
Qe 
