Comparative study on the determination of carbonate content in rocks between gasometric method and subtraction method
A comparative study was conducted in the aspects of experimental condition method detection limit,accuracy,precision,significant test to determine the difference between gasometric method and subtraction method in the carbonate content analysis for rock samples.The results showed that the gasometric method has strict requirements for the environment temperature and atmospheric pressure.For every 1℃change in environmental temperature,there will be a 0.34%difference in the determination results of carbonate content;for every 100 Pa change in atmospheric pressure,there will be a 0.10%difference in the measurement results of carbonate content.Therefore,the gasometric method should be carried out under a constant temperature and pressure condition.In contrast,changes in temperature and pressure have almost no effect on the measured results of subtraction method.the detection limit of gasometric method was 0.02%,which was less than the detection limit of subtraction method 0.04%.The repeatability testing,which measured rock samples with low,medium and high carbonate content for 6 times respectively,was conducted between these two methods to determine the relative standard deviation(RSD)of the samples,which was less than 5%.The precision results of both methods were good.Different kinds of rock certified reference material were tested to check accuracy and the results were all with the range of uncertainty for both methods,indicating that the accuracy of both methods met the requirements.According to significant test analysis,the t-values calculated by both methods were less than 2.228 in the light of the t-test critical table,suggesting that there was no significant difference in the measurement results of carbonates content in rocks between the gasometric method and the subtraction method under a confidence level of 95%.The gasometric method requires a large amount of 0.5～10 g rock samples,which is much higher than the subtraction method,which requires 0.2 g.Gasometric method and subtraction method both can accurately and precisely determine carbonate in rock samples.In actual testing work,gasometric method is preferred for measuring samples with small quantities,and subtraction method has advantages in the efficiency of analyzing large batches of samples.
gasometric methodsubtraction methodcarbonate contentcomparative study
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