Molecular Volumes of Mononuclear Aromatic Hydrocarbons NANCY CORBIN, RIARV ALEXIhDEK, LND GUSTAV EGLOFF Cniversal Oil Prorlrtcts Coriaprrri>, Cliicrcpo, 111.
I i ~ o r noil? aeries to nriothcr and are charticteristic of the series. The density d:ita used to calculate the nio1crul:ir volume:: :Lre values found in the literature (4). When the molecular volume a t a temperature other than 20" C. was required, it n-as calculated from the "best" value of the density a t 20" C. and the temperature coefficient of density. I n some cases no equation for the varixtion of density with temperature has been calculated. However, the temperature coefficient of density for hydrocarbons has hcen shown t o bear a definite relationship t o molecular neight ( 1 7 ) . Thus, the Constants of a density-temperature equation for any hydrocarbon may be accurately estimated from the molecular weight. These estimated values, in conjunction with the density a t some given temperature, Rere used t o determine the moleculnr volume of compounds for whirh the c%sperimental data were inadequate. I n order t o compare molecular volumes at. corresponding reduced temperatures, the critical temperatures must be known. The witical temperature of a compound may he calculatccl from the boiling point and thc parachor (11) if the experimental values are not availnble. The boiling points used in calculating the critied tempcixtures were the calculated values from 3 previous study on mononuclear nromatic hydrocarbons (3). These boiling points in most cases agree ~ v e l with l the expcriniental values. Calcu1:ited v:iluvs for critical temperatures were u ~ c c lthroughout this study. The calculated and experimental ~--nlur\snrri sholvn in l':ihlc I. The experimcrital values in thc table' : i r ~:i\~r.ages ( i f :ill the availnble data in the literature nnd n-cw tnkcn from I:yloff (4). 'The requirement t h a t both dcnsity :ind boiling point data be :ix~nilnhlcfor romparisons of molrmilnr volumrs nt retluctd tem-
T h e inolecular *oluniesof 1-phenylalkanes and 2-pheii) 1alkanes at any @\en fraction of the critical temperature are linear functions of the nuniber of carbon atoms. RIolecuIar \ olunies of fourteen homologous series of mononuclear aromatic h>drocarbons at 20' C. are also linear functions of the number of carbon atonis. Both of these relationships may be expressed by equations of the forni :
M/d = V = a
-+ bn
Constants a and b are simple functions of the reduced temperature. These functions may be expressed by equations of the form : a or b = k
+ pT8 4-q T i
THE
study reported her
