VOl. 29 Automated analysis of nitrogenous compounds 89 some gross errors in a simple graph-reading exercise in which the readers were aware that the results were to be analysed for correctness. On the whole the gain in precision in going from the non-linear, hand-drawn chart technique (where the main error is probably in absolute accuracy) to the semilog computed standard curve is fairly small, but the importance of precision was shown to us in our routine laboratory serum calcium estimations,

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... n which transcription is carried out by the Wang technique. Comparison of recovery of a quality control serum for runs over a period of 3 months in which transcription was by manually drawn graphs with those from 3 months of the Wang technique showed a halving of the coefficient of variation from about 7:/0 to 3'5%.