Charge reduction and regeneration in K+, Na+, Mg2+, Ni2+ and Co2+-exchanged Wyoming Bentonite

Controlled calcination of ion-exchanged Wyoming Bentonite in the presence and absence of ammonia leads to layer charge reductions. Detailed chemical analyses of both unexchangeable and exchangeable species lead to the conclusion that in no case is there migration of the original interlamellar cations into the octahedral region of the layers although, in terms of ionic radius alone, Mg²⁺, Ni²⁺ and, possibly Co²⁺, might be expected to do so. The production of unexchangeable Mg, Ni or Co, is identified as resulting from high temperature hydrolysis leading to hydroxide or oxide formation.     

Transfer function synthesis using a finite-gain amplifier

An active RC circuit employing a single finite–gain amplifier, one two–port and two ono–ports, has been presented here for the realization of n general voltage transfer function without positive real axis zeros. The comparative merits of the scheme with respect to that proposed by Rao (1969) are that the synthesis procedure is simpler and the number of passive circuit elements required is smaller. The coefficient of realization of the synthesized transfer function can always be made equal to unity with the scheme. A few examples are included to illustrate the synthesis procedure.