MABERY. — CONSTITUENTS OF PETROLEUM. 178 



Even the mixtures that the crude Pennsylvania distillates have proved 

 to be are much lower in specific gravity than those with the same boiling 

 points from Russian oil. After purification, the Pennsylvania distillates 

 unquestionably have the composition of the series C„H2„+2- 



Allusion has been made to the great difficulty in removing entirely the 

 constituent with less hydrogen from the distillates prepared tor analysis, 

 and also to the fact that, even after the most thorough purification, the 

 specific gravity of the purified distillate is appreciably higher than that of 

 the hydrocarbon with the same boiling point prepared by synthetic methods. 

 These facts may indicate the presence in small quantity of naphtenes 

 which are acted on only very slowly by reagents, especially when largely 

 diluted in the main body of the principal constituent. 



Structure of the Petrgleuji Hydrocarbons, 160°-216°, 



lu comparing the petroleum hydrocarbons with the corresponding bodies 

 synthetically prepared, it is but fair to state that the literature of the latter 

 is not altogether satisfactory. The properties of normal decane as it 

 was prepared by Lachowicz,* by the action of sodium on a mixture of 

 normal octyl bromide and ethyl iodide, and also by Kraflft,! by heating 

 caprinic acid with a mixture of hydriodic acid and phosphoric penta- 

 chloride, seem to define the corresponding petroleum hydrocarbon as 

 the normal compound. 



The boiling point of the hydrocarbon synthetically prepared is 173° 

 under 760 mm., and its specific gravity 0.74o6 at 0°. The boiling point 

 assigned by me to petroleum decane is 173°. 5, and its specific gravity at 

 20° is (from Pennsylvania petroleum) 0.7486. Evidently the decane 

 obtained by Thorp and Young by heating solid paraffine, boiling at 166°- 

 168°, specific gravity 0.7394 at 13°. 5, is an impure normal hydrocarbon. 



A decane has been obtained by several methods, boiling at various 

 temperatures between 157° and 162°. Active diamyl boiling at 159°- 

 162°, specific gravity 0.7463 at 22°, with a high dextro rotatory power, 

 was obtained by Just, on treating active amyl iodide with sodium. But 

 the petroleum decane has not the same form, since it shows no influence 

 on polarized light. The latter has with greater probability the same form 

 as diisoamyl, obtained by Wurtz on heating isoamyl iodide with sodium. 

 The boiling point of this secondary decane is given by Wurtz as 158°, 

 with no mention of barometric tension, and specific gravity as 0,7413. 



* Ann. Chem. Pharm., CCXX. 179. 



t Ber. der deutsch. chem. Gesellsch., XV. 1695. 



