Na- and K-exchange experiments on laumontite

Laumontite, Ca4Al8Si16O48. nH(2)O, was treated for 22 weeks at 150 degrees C in 1.5 M Na2CO3 and K2CO3 solutions of pH 11.3. The exchange products wer e studied by X-ray powder diffraction and electron microprobe analyses. In Na2CO3 solution laumontite transformed to analcime, Na2Al2Si4O12. 2H(2)O (c ubic, a = 13.7234(8) Angstrom), calcite, and very minor cancrinite. In K2CO 3 solution laumontite reacted to merlinoite, K8CaAl10Si21O64. nH(2)O (ortho rhombic, a = 14.155(7), b = 14.169(4), c = 10.023(4) Angstrom), and calcite . Completely alkali exchanged laumontite could not be obtained. After 9 wee ks of exchange residual laumontite had the composition Na4.34K0.03Ca1.72Al7 .83Si16.17O48. nH(2)O, and K3.99Na0.01Ca1.96Al7.92Si16.08O48. nH(2)O, respe ctively.