A NOTE ON THE STRUCTURE OF ACETYLENE 



BY ALBERT P. MATHEWS 



From a study of the volume of liquid acetylene, Macintosh 1 

 concluded that acetylene was in reality acetylidene since one 

 of the carbon atoms seemed to have the volume of bivalent 

 carbon. He supported this contention also by various chem- 

 ical arguments. On the other hand, Nef, 2 while showing 

 that the halogen substitution products were in reality acetyl- 

 idene compounds, believed that acetylene was acetylene 

 and not acetylidene, because it was chemically and physiolog- 

 ically so inert. Nef's pupil, Lawrie, 3 confirmed the acetylidene 

 nature of the bromine and iodine substitution products. 



Although it is improbable, for the reasons stated by Nef, 

 that acetylene is acetylidene, the matter may be definitely 

 settled by my method of 4 determining the number of valences 

 in the molecule from the molecular cohesion. If it is acetylene 

 there should be ten valences; if acetylidene, there should be 

 eight, since acetylene does not associate and one carbon atom 

 would be bivalent. 



The most recent determination of the critical data of 

 acetylene by Cardoso and Baume gives T c , 35.5 C; and P c , 

 61.6 atmospheres. From these figures the value of "a" of 

 van der Waals' equation calculated by the formula: a = 

 27T c 2 /64 X 273 2 X P c , is 0.008745. Computing the number of 

 valences, n from "a" by the formula: n = a 3/2 X 3.2 X 



1 Macintosh: "The Physical Properties of Liquid and Solid Acetylene," 

 Jour. Phys. Chem., n, 315 (1907). 



2 Nef: "Ueber das zweiwertige Kohlenstoffatom," Liebig's Ann., 298, 332 

 (1897)- 



3 Lawrie: "Constitution of Acetylidene Compounds," Am. Chem. Jour., 

 36, 487-510 (1906). 



4 Mathews: "The Relation of the Value 'a of van der Waals' Equation 

 to Molecular Weight and the Number of Valences of the Molecule," Jour. Phys. 

 Chem., 17, 181 (1913)- 



