578 PROCEEDINGS OF THE AMERICAN ACADEMY. 



0.7830 at §£, and 0.7816 at %. Krafft gave 0.7768 as the specific grav- 

 ity of C 18 H 38 at 28°. A determination of the molecular weight of the 

 purified hydrocarbon confirmed its formula : — 



1.1003 grm. of the oil and 19.65 grms. benzol gave a depression of 0.941. 



Calculated for C 18 H 37 C1. Found. 



288.5 291.5 



This molecular weight, showing that the hydrocarbon boiling at 300° 

 is octodecane, does not agree with Krafft's conclusion as to the formula 

 of the hydrocarbon obtained from stearic acid. In heating stearic acid 

 with hydriodic acid Krafft assumed that all the oxygen is removed, 

 leaving intact the carbon of the carboxyl, with the formation of octo- 

 decane. But when this work was done the only means of verifying the 

 formula was by analysis, which was sufficient to determine the series, 

 but not the individual members of the series. While the results of 

 Krafft's combustions gave almost exact values for the formula C 18 H 38 , the 

 size of the molecule could not be determined. Krafft looked upon the 

 hydrocarbon boiling at 303° as having the formula Ci 7 H 36 . 



The specific gravity of the oil after cooling and filtration was some- 

 what higher than before, 0.8110 at 20°, and higher than the specific 

 gravity of the filtered solid octodecane, 0.7830. The molecular weight 

 of the filtered oil was the same as before filtration. 



0.9904 grm. of the substance and 16.10 grms. benzol gave a depression 

 of 1°. 184. 



Calculated for C ]8 H 38 . Found. 



254 254.6 



A combustion of the liquid hydrocarbon showed some change in the 

 proportions of carbon and hydrogen : — 



0.1483 grm. of the substance gave 0.4636 grm. C0 2 and 0.1954 grm. FLO. 



While there is a narrow difference in calculated percentages between 

 the two formulae, the percentages found, together with the higher specific 

 gravity, indicate that the filtered oil was a mixture of the two series C n H n2 

 and H n a 



• / 2n+2* 



