Microdetermination of Calcium in Saliva and Serum.

Summary. A method for determination of calcium in about 0.3 ml serum or 1.0 ml saliva (0.02 to 0.05 mig of calcium) is reported. The principle is the same as that indicated by SOBEL and SKLERSKY, but the procedure is somewhat different. The duration of the procedure has been shortened and the accuracy has been increased by the introduction of a number of improvements. The principle is: The calcium is precipitated as oxalate. The oxalate is converted by ignition to carbonate, dissolved in a hot solution of 10 per cent boric acid, and titrated with a 1/10 n hydrochloric acid to the pH of the pure boric acid. When 24 samples are treated together the procedure requires 3 hours up to and including the precipitation and 3 hours more for the final treatment and the titrations. The percentage error of the single determination is about 0.7 for 0.05 mg of calcium.