the Elements Carbon, Buron } and Silicon. • 301 



number of facts connected with the heat of combination of car- 

 bon which have hitherto appeared anomalous seem to find their 

 explanation in this variability of the carbon atom. Thus the 

 heats of combination in certain reactions are as follows: — 



C,0 =2398 heat-units C a , H 9 = -4584] referred to i 

 C, 2 =8097 „ C 2 , H 4 = - 906 ^^^011 



CO,O=5607 C, H 4 = 1701 J im-oica»Don. 



On the assumption that the nature of the carbon atom does not 

 vary, these facts are difficult of explanation. Regnault's results 

 regarding the specific heats of liquid and gaseous carbon com- 

 pounds*are explained byadoptingthe hypothesis that the natureof 

 the carbon atom varies in its different compounds. The great va- 

 riations in the specific heats of the liquid carbon compounds ob- 

 served by Regnault are due, not to the fact that these compounds 

 are liquids, but to the immediate influence of the carbon atoms 

 contained in these compounds. Hence all Regnault's endeavours 

 to establish a relation between the varying specific heats of the 

 liquids and their relative volumes must be fruitless. The un- 

 known cause which Regnault admits, in the last words of his 

 research, " on est oblige d'adrnettre qu'en outre des causes, telles 

 que la dilatation, qui font certainement varier la capacite calori- 

 fique d'un meme corps avec la temperature, il en existe d'autres, 

 que nos moyens d'investigation ne sont pas parvenus jusqu'ici 

 a defmir," is to be found in the varying specific heat of the car- 

 bon atoms, which changes with the changes of temperature and 

 of molecular constitution. Regnault, in his researches upon the 

 specific heats of gaseous carbon compounds, gives merely the 

 mean result for a certain temperature-interval, except in the case 

 of carbon dioxide ; from these mean results little can be deduced, 

 if it be true that the specific heat is a function of the tempera- 

 ture, as in these cases the nature of this function is unknown. 

 It is only from widely extended researches upon the specific heats 

 of a number of gaseous and liquid carbon compounds that any 

 deep insight can be obtained into the nature of carbon, and into 

 the general laws regulating the specific heats of the compounds 

 of this element. With this work I am now engaged; but some 

 time must elapse ere my results are sufficiently advanced for 

 publication ; I have therefore summarized the points of interest, 

 and showed the consequences which seem to follow from my 

 researches, so far as these have been carried out. 



(3) The question has yet to be answered, How, in reference to 

 the atomic constitution of the elements carbon, boron, and sili- 

 con, can we on physical grounds harmonize all the foregoing 

 results regarding the specific heats of these elements ? Only 



* Mem. de V Acad de Paris, vol. xxvi. 



