with 200 u03bcl of a solution of phenolsulfonephthalein a dye which forms a blue colored stable complex in the presence of free calcium after incubation for 3 minutes an intensity of coloration measured at 612 nm which is directly proportional to the calcium concentration in the sample is obtained in each plate a calibration range is prepared using the following concentrations of calcium 0 0 5 1 1 5 2 3 4 5 mm it was noted fig2 that the bcp in microparticle form and also the ha powder brought into contact with plasma induced a considerable and significant decrease in the calcium concentration of said plasma the decrease in calcium concentration is similar for bcp and ha and is not observed for u03b2 tcp on the basis of the values obtained for the plasma alone 1 960 u00b1 0 044 mm the plasma in the presence of bcp 0 871 u00b1 0 160 mm and the plasma in the presence of ha 0 840 u00b1 0 121 mm the calcium uptake was evaluated at 0 125 u03bcmol of calcium per 50 mg of bcp or ha it was also noted that the addition of 50 u03bcl of a 2 5 mm solution i e 0 125 u03bcmol to the bcp or the ha before addition of the plasma made it possible to restore a normal plasma calcium concentration fig2 the same amount of calcium chloride added to u03b2 tcp adds to the initial plasma calcium and confirms the absence of uptake by this biomaterial under these conditions moreover it was observed that the.