In quantitative spectrographic analysis, the normal density, D =log (opacity) as measured quantity, has been most widely used, but recently so-called Seidel-density, W=log (opacity-1) .,or so-called P-density, P= (D+W)/2 has often been used. But it has not been evidently confirmed that in which case the density W or P should be used, and in which points W or P is more favourable than the normal density. The author has made a theoretical study on the working-curve of the internal-standard method

more »

... and compared the working-curve in Seidelscale with that in the normal-scale from the point of view of the errors. The results of this study are summarized as follows: 1. The slope of working curve in Seidel-scale is steeper than that in normal scale. 2. In practical concentration range, errors are sufficiently eliminated in the internal standard method, using the normal scale, but in this range it does not necessarily follow that the errors is sufficiently eliminated in Seidel-scale. 3. In low concentration range sometimes Seidel-scale is more favourable but sometimes is not. Generally speaking, Seidel-scale is more favourable in case of the slope of working curve in this scale, being extremely steeper than that in normal scale.