30 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Between 87° and 93°, 80 grams collected after the sixth distillation, 

 and in the portion which distilled constant at 89°-90°, bar. 754 mm., 

 a vapor density determination gave 3.43 ; required for isoheptane, 

 3.46 ; boiling point, 90°. 4 (Warren). 



At the end of the sixth distillation, 175 grams collected at 96°-99°, 

 and 50 grams distilled constant at 9G°-97°, bar. 744 mm. ; a vapor 

 density determination of this product gave 3.42 ; required for heptane, 

 3.6 ; boiling point of heptane, 98°. 7 (Warren). Above this point the 

 distillates were small in amount to 109°, where other products began 

 to appear; between this limit and 120° the single degree fractions 

 were considerable in quantity. 



At 118°-120°, 120 grams were collected, of which 50 grams dis- 

 tilled constant at 119°-120°, bar. 749 mm. This product gave a 

 value in a determination of its vapor density required for octane : 

 found, 3.98 ; required, 3.94. Since some doubt has been expressed 

 concerning the existence of an octane with this boiling point, this 

 fraction was carefully purified for analysis with alcoholic mercuric 

 chloride, nitric acid, and sulphuric acid, and it was finally submitted to 

 prolonged boiling with sodium. Determinations of carbon and hydro- 

 gen then gave the following results : — 



I. 0.1707 gram of the oil gave 0.5282 gram COo, 0. 1707 gram H2O. 

 11. 0.2017 gram of the oil gave 0.6237 gram CO., 0.2737 gram H^O. 



The low percentage of hydrogen evidently indicated that the 

 octane was still contaminated by a hydrocarbon containing less hydro- 

 gen. For further purification the oil was heated to boiling during 

 several hours with a mixture of nitric and sulphuric acids, and boiled 

 several times with sodium. It then gave the percentages of carbon 

 and hydrogen rquired for octane: — 



There seems to be no question that the fraction 118°-119° contains 

 a hydrocarbon with the composition required for octane, and this 

 observation is apparently confirmed by the results of others. War- 



