AKD COMPOSITION IN OEGANIC COMPOUNDS. 
259 
held from a field where our knowledge, emanating from earlier observations, but 
expanded and consolidated more than ever before by recent experimental evidence, has 
already gained a solid foundation. 
It is especially with regard to organic compounds that constant relations between 
boiling-point and composition have been demonstrated. It often occurs that in the case 
of analogous compounds the same difierence in the boiling-points corresponds to the 
same difierence in the chemical formulae, or that the difierences in boiling-points and 
those in composition are proportional. In different series of analogous compounds the 
same differences of boiling-point may correspond to the same differences of composition, 
but this does not obtain in all series. The regularities exhibited by the boiling-points 
of organic compounds, and more especially the observation of the same difference of 
boihng-point corresponding to the same difference of composition, are limited to certain 
groups. In other groups, the same difference in the formulae involves another difference 
in the boiling-points. 
Among the earliest recognized regularities, comprising at the same time the largest 
number of compounds, are the following: — An alcohol €„ 11 ^+ 2 Og, which contains 
more or less than another, boils at a temperature xXl9° higher or lower. 
An acid Cn O 4 , boils at a temperature 40° higher than the alcohol the 
oxidation of which may give rise to the acid. A compound ether O 4 , boils at a tem- 
perature 82° lower than the acid C„ O 4 isomeric with it. If we start from the boil- 
ing-point of ethyl-alcohol =78°, these three propositions enable us to calculate the 
boihng-points of a large number of organic substances, alcohols, acids, and compound 
ethers, represented by the above general formulae, as given in the following Table : — 
Table I. 
Calculated boiling-points. 
Alcohols CnHn+ 2 O5. 1 
1 
Acids Cn Hn O4. 
Compound ethers Cn Hn O4. 
c , H4 O2 
0 
59 
c , n , O4 
0 
99 
C4 H4 O4 
36 
C4 H, O2 
78 
C4 H4 04 
118 
C„ H, 0 
97 
116 
c, H, 0. 
137 
156 
Ce H3 O4 
55 
c, H,„0, 
c» 0. 
C3 H, O4 
74 

135 
c,„h,„04 
175 
Cio O4 
93 
Cj 2 Hj 4 02 
154 
C,2H,2 04 
194 
C12 O4 
112 
173 
192 
213 
C,4 H 4 O4 
131 

^16 ^13 ^2 

C16 H,3 O4 
232 
C16 H,3 O4 
150 

211 
C18 Hig 0^ 
251 
C48H,3 04 
169 
C20 H22 02 
230 
C20 Hjo O4 
270 
C20 O4 
188 
^22^2102 
249 
C22 H22 O4 
289 
C22 ^22 O4 
207 
C2.H,,0, 
268 
C24 ^24 O4 
308 
C24H24O4 
226 
C28H,3 02 
287 
C26 ^26 ^4 
327 
^28 lUe ®4 
245 
C28H30O, 
306 
C28 H23 O4 
346 
^28^^28 04 
264 
C30H32O, 
325 
C3oH3„0, 
365 
C30H30O4 
283 
C32 H34 0, 
344 
C32 ^32 O4 
384 
C32H32O4 
302 
The degree of accuracy with which the numbers of this Table represent the boiling- 
points of the several substances, may be gathered from a comparison of these numbers 
2 M 2 
