Nitrogen in oil shale and shale oil. V. The determination of nitrogen in shale oil and oil shale

The application of the Kjeldahl method for the determination of the nitrogen content of crude petroleum and crude shale oil has been attended by difficulties which appear to have been due mainly to the failure to appreciate fully the various factors involved.For example, when determining the nitrogen content of crude shale oil, Petrie (1) found that twenty days' digestion with sulphuric acid were necessary before the mixture cleared.Since that time, however, catalysts have been used together with added sodium or potassium sulphate in order to speed up the digestion.The U.O.P. method for the determination of nitrogen in petroleum (2) recommends the continuation of the digestion for from one-half to five hours after the acid clears, but gives neither a reason of the extended time nor any indication of its importance.This method is a simple adaptation of the first successful application of the Kjeldahl method for the determination of nitrogen in petroleum by Poth et al. (3).These workers used a mercuric oxide-copper sulphate catalyst with potassium sulphate to raise the temperature of the digestion mixture, and they found that, in order to recover all the nitrogen present, it was necessary to continue the digestion for five hours after the acid had cleared. ShaleOil.