An Improved Procedure for Wet Oxidation of the 14C NBS Oxalic Acid Standard
C 13 C 12
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CitationValastro, S., Land, L. S., & Varela, A. G. (1977). An improved procedure for wet oxidation of the 14C NBS oxalic acid standard. Radiocarbon, 19(3), 375-382.
PublisherAmerican Journal of Science
AbstractAn improved procedure for wet combustion of 14C NBS oxalic acid standard has been devised which gives consistent high carbon yields and average delta-13C values of -19.1 per mil. The principal cause of fractionation in earlier attempts to prepare CO2 by the wet oxidation method was the inexact nature of the end-point. The new procedure employs a chocolate-brown end-point by adding 5ml more of the sulfuric acid-potassium permanganate solution after the initial reddish brown end-point is reached. The sulfuric acid-potassium permanganate solution is added to the NBS oxalic acid in a steady drop-wise flow, heat is applied to the generating apparatus, and a cycling technique is utilized to collect the CO2. Fifteen samples of the NBS oxalic acid were processed. The per cent carbon yields range from 98.8 to 100.9% with an average of 99.7% and an average delta-13C of -19.12 per mil. The results obtained by this procedure are much more consistent than previous results obtained in several laboratories by direct combustion.