ELASTIC PROPERTIES OF SULFANILATES OF LI, NA, K, RB, CS, TL, NH4, CH3NH3 AND C(NH2)(3)

Single crystals of optical quality and dimensions LIP to 60 mm of sulf anilates of Li, Na, K, Rb, Cs, Tl, NH4, CH3NH3 and C(NH2)(3) have been grown from aqueous solutions by controlled lowering of temperature an d slow evaporation between 315 K and 290 K. All species except the sul fanilates of methylammonium and guanidinium form hydrated phases withi n that temperature range. Thallium sulfanilate crystallizes simultaneo usly in two phases, a metastable monohydrate and a stable hemihydrate. The sulfanilates of Na, K, Rb and Tl (monohydrate) possess orthorhomb ic symmetry, the others monoclinic symmetry. Except the cesium salt th ey all exhibit an inversion center. The elastic constants cli and thei r derivatives T-ij = d log c(ij)/dT, T temperature, have been determin ed from ultrasonic resonance frequencies of thick plates and their var iation with temperature, respectively. In addition, the tensor of ther mal expansion has been measured. The anisotropy of the longitudinal el astic stiffness shows a close relation to the arrangement of the sulfa nilic anions. The contribution of the hydrogen bonds to the elastic st iffness is clearly recognizable. The structurally inhomogeneous group obeys to a large extent the rules governing the mean elastic and therm oelastic behaviour of ionic crystals.