| 摘要 |
PURPOSE:To measure the concn. of a minute amount of calcium in good preciseness by an absorption photometry without receiving the influence of a magnesium salt or the like, by a method wherein glycine or aspartic acid is added and alizarin acid black SN is further added to perform colorimetric analysis. CONSTITUTION:After a NaOH 10% solution is added to an aqueous 7% Na2SO4 solution containing a minute amount of calcium and magnesium to adjust the pH thereof to 11.5, an aqueous 1% glycine solution is added to and mixed in the pH adjusted solution. In the next step, an aqueous 0.1% alizarin acid black SN solution is added thereto and pure water is added to measure absorbency by a spectrophotometer. When the aqueous solution of glycine or aspartic acid is added, the influence of a magnesium ion is not received even if it is present at pH of 11.5-13.0. The addition amount of glycine or aspartic acid is sufficient if added in an amount of 0.0001wt% or more. The addition amount of arizarin acid black SN as an indicator is 0.0001-0.01wt%. |
