The brittle mica-like KNiAsO₄ and its organic derivatives

The nickel arsenate KNiAsO 4 has a mica-like layer structure with surface charge densities similar to brittle micas. In contrast to micas it easily exchanges alkylammonium ions. The interlayers have paraffin-type chain arrangements, as in alkylammonium vermiculites and alkylamine smectites and vermiculites, but the very regular chain packing causes a marked odd/even alternation of the basal spacings. The reactions of KNiAsO 4 throw light on the exchange behaviour of micas.