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An Improved Procedure for Wet Oxidation of the 14C Nbs Oxalic Acid Standard

Published online by Cambridge University Press:  18 July 2016

S Valastro Jr. ,
L S Land  and
A G Varela
S Valastro Jr.
Affiliation:
Radiocarbon Laboratory, University of Texas at Austin, Balcones Research Center, 10100 Burnett Rd, Austin, Texas 78758
L S Land
Affiliation:
University of Texas at Austin, Dept of Geological Sciences, Austin, Texas 78712
A G Varela
Affiliation:
Radiocarbon Laboratory, University of Texas at Austin, Balcones Research Center, 10100 Burnett Rd, Austin, Texas 78758
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Abstract

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An improved procedure for wet combustion of 14C NBS oxalic acid standard has been devised which gives consistent high carbon yields and average δ13C values of —19.1‰. 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 δ13C of —19.12‰. The results obtained by this procedure are much more consistent than previous results obtained in several laboratories by direct combustion.

Type
Research Article
Information
Radiocarbon , Volume 19 , Issue 3 , 1977 , pp. 375 - 382
Copyright
Copyright © The American Journal of Science 

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