[Experimental study on usage and dosage of gypsum].

The content of calcium ion Ca2+ in gypsum decoction has been determined with coordination titration. Observation and comparison have been conducted of the relationship between the dosage, comminution degree, decocting time and decocted contents. The results show that the dosage of gypsum should be 10-20 grams, preferably ground to at least 60 mesh powder, the fine powder over 60 mesh is not to be pre-decocted, but the coarse powder of 40 mesh needs pre-decocting.