MABERY. — SULPHUR PETROLEUMS. 21 



oil from the amount found in the coke, there is some uncertainty as to 

 the quantity of oil corresponding to the coke. In some oils the pro- 

 portion of residue is estimated as ten per cent of the crude oil. It 

 depends also upon the method followed by the refiner. Sometimes 

 the first distillation of the crude oil is pushed to the point of com- 

 plete decomposition, and the tar distillate is again distilled until it is 

 coked. It is well known that earthy matter frequently remains for 

 some time in suspension in the crude oil after it is taken from the 

 wells. On this account, if the oil was distilled before the suspended 

 material had subsided, the ash would not represent what had been in 

 solution in the oil. But the oil is usually allowed to stand some time 

 before distillation, and that the coke we examined was practically free 

 from suspended matter is evident from the low percentage of ash, and 

 corresponding results with Canadian oil where the ash was determined 

 in a tar distillate and in coke from crude oil ; the percentages of ash 

 from the two sources were not very different.* 



In Findlay oil, in which our determination was made, the proportion 

 of still residue is doubtless somewhat smaller than that mentioned 

 above, probably between ten and five per cent. The corresponding 

 percentage of ash iu the crude oil would, therefore, be not far from 

 0.005 per cent, an amount considerably less than MarkownikofF and 

 Oglobliu found iu Russian oil. 



An analysis of the ash showed that it was composed chiefly of 

 lime and magnesia, and the ({uantity of magnesia is at least equal to 

 that of the lime. Traces of iron and aluminum were found, the iron 

 possibly having been dissolved from the £,till. It is therefore evident 

 that the crude oil has exerted an appreciable solvent action on the 

 limestone reservoir, dissolving both constituents of the dolomitic rock. 



It is maintained by some chemists that all petroleums contain the 

 same series of compounds iu different proportions, and that the differ- 

 ence in properties depends upon a variation in the quantities of the 

 constituents. In a general sense, with respect to the principal series 

 of hydrocarbons this is, doubtless true; yet there is such a wide 

 difference in the properties of oils like those from Pennsylvania 

 and the Caucasus that they are characteristic of substances quite 

 unlike. The Caucasus petroleum is wholly, or nearly, wanting in 

 the series C„H2,i^_2. and the Pennsylvania oil evidently contains the 

 series C„H2„ in much smaller proportion than the Russian oil. The 

 presence of the higher members of the latter series in the Pennsyl- 



* Determination of Ash in Canadian Petroleum, page 51. 



