258 DE, HEEMANN KOPP THE EELATION BETWEEN BOILIXG-POIN'T 
and that the isomeric compound ethers differed from one another in them boiling-points. 
An extensive series of boiling-point determinations * which I made of these isomeric 
ethers, proved that the latter assumption is not founded on facts. The exertions made by 
ScHEODER, Gerhardt, Lowig and others, in the hope of recognizing the influence of the 
constituent elements on the boiling-point of a compound, have also essentially remained 
without result f. 
In France the existence of the relations between composition and boiling-point which 
I had observed, has been contested by I. Pierre J, who determined the boiling-points of 
many organic compounds, while engaged in an inquiry regarding their expansion. In 
England, lastly, W. A. Miller § has likewise called attention to the discrepancies 
between the boiling-points observed by Pierre and those calculated on the supposed 
existence of the relations which I had indicated. I was, however, enabled || to remove 
these apparent discrepancies by the first results obtained in a long series of experimental 
observations of my own, in which, at intervals and as material and opportunities pre- 
sented themselves, I have continued up to the present day. 
The existence of the relations between composition and boiling-point, such as it 
results from my original observations, has, notwithstanding these objections, been gene- 
rally acknowledged. In many cases the recognition of these relations furnished im- 
portant arguments in discussions regarding the true molecular value of organic com- 
pounds. Chemists have observed a vast number of new illustrations, and for several 
series, in which the individual terms differ from each other by a constant elementary 
difference, the corresponding difference of boiling-point has been carefully determined^. 
Nevertheless, these relations, the important means of control which they afford in expe- 
rimental inquiries, and the assistance which they are frequently capable of lending in 
the determination of the true chemical character of a new compound, have scarcely been 
sufiiciently appreciated. 
The rapid progress of organic chemistry has greatly expanded the material available 
for the discussion of boiling-points, and up to the latest date the stream of experimental 
inquiry, whilst confirming or correcting former observations, has furnished a rich supply 
of additional important facts. The time has arrived when a survey of the teriitory safely 
acquired may be taken, and when from the boundary lines reached we may fix the 
directions in which we have next to advance. 
A collection of my researches on this subject in a connected form, permitting this 
survey, and showing the results which may be expected from their application, I now 
beg leave to submit to the Koyal Society, hoping that their attention may not be %vith- 
* Ann. der Chem. und Pliarm. vol. Iv. p. 166. 
t In reviewing ScHBonER’s memoir on this subject, I have pointed out the reasons which render the 
general solution of this problem almost hopeless. — Pogg. Ann. vol Ivvxi. p. 37-1. 
J These soutenue a la Paculte des Sciences a Paris (Annuaire de Chimie, par Millox et Eeiset, 1S46). 
§ Quarterly Journal of the Chemical Society, vol. i. p. 363. || Ibid. vol. iii. p. 104. 
^ The careful manner in wliich A. II. CnuRcn (Phil. Mag. [4] ix. 256) has determined the difierence of 
the boiling-points for the series of hydrocarbons Cn Hn-c, deserves especially to bo mentioned. 
