CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 CASE SCHOOL OF APPLIED SCIENCE. — NO. XL. 



ON THE SPECIFIC HEATS AND HEAT OF VAPORI- 

 ZATION OF THE PARAFFINE AND METHYLENE 

 HYDROCARBONS. 



By Charles F. Mabeky and Albert II. Coldstein. 



Received February 10, 1902. Presented February 12, 1902. 



Since 1819, when Dulong and Petit, on the basis of their work on 

 thirteen of the chemical elements, announced the law that atoms of all 

 elementary bodies possess the same capacity for heat, or that the specific 

 heats of the elements vary inversely as their atomic weights, the specific 

 heats of the elements have been important physical constants. With 

 some exceptions, the constant 6.54 represents the product of the atomic 

 weight into the specific heat. Later work showed that this law could be 

 extended to compounds. In 1831, Neumann discovered that compounds, 

 with analogous composition have the same specific heat. Or in a series 

 of compounds with analogous composition the specific heat varies inversely 

 with the molecular weight. These laws apply to approximately forty ele- 

 ments and to solids only at temperatures much below their melting points. 

 The specific heats of many organic compounds have since been deter- 

 mined, and although no law has been stated, it is evident that, in certain 

 homologous series of organic compounds, a condition exists in some of 

 these series analogous to the law of Neumann. For instance, deter- 

 minations have been made on a few of the alcohols with the following 



results * 



Ethyl alcohol 0.680 



Iso-propyl alcohol 0.5286 



Iso-butyl alcohol 0.5078 



Iso-amyl alcohol 0.49,'] 2 



That the variations on certain homologous series so far as they have 

 been observed do not conform to a general law, is shown by the follow- 

 ing series, in which the specific heats increase with increase in molecu- 

 lar weights : 



