Production of 34S labeled gypsum (Ca34SO4•2H2O)

Agricultural gypsum (CaSO4 center dot 2H(2)O) stands out as an effective source of calcium and sulfur, and to control aluminum saturation in the soil. Labeled as S-34 it can elucidate important aspects of the sulfur cycle. Ca(34)SO(4 center dot)2H(2)O was obtained by chemical reaction between Ca(OH)(2) and (H2SO4)-S-34, performed under slow agitation. The acid was produced by ion exchange chromatography using the Dowex 50WX8 cation exchange resin and a (Na2SO4)-S-34 eluting solution. After precipitation, the precipitate was separated and dried in a ventilated oven at 60 degrees C. From 2.2 L H2SO4 0.2 mol L-1 and 33.6 g Ca(OH)(2), 73.7 +/- 0.6 g (CaSO4)-S-34 center dot 2H(2)O were produced on average in the tests, representing a mean yield of 94.6 +/- 0.8%, with 98% purity. The (SO2)-S-34 gas was obtained from (CaSO4)-S-34 center dot 2H(2)O in the presence of NaPO3 in a high vacuum line and was used for the isotopic determination of S in an ATLAS-MAT model CH-4 mass spectrometer.