ON THE MOVING BOUNDARY METHODS FOR THE DETERMINATION OF CATAPHORETIC SPEED OF COLLOIDS. PART II.

The suitability of the moving boundary method as developed by Mukherjee for the determination of cataphoretic speeds of concentrated colloids in which the electrical conductivity of the colloid particles is comparable with those of the interruicellary electrolytes has been discussed in the light of the electrolytic migration theory of Kohlrausch and Weber. This theory has been verified with mixtures of KCl and KlO3. The conditions necessary for reliable cataphoretic measurements have been experimentally secured with two ferric oxide and two aluminium oxide hydrosols and cataphoretic speeds generally reproducible within a% have been obtained. The cataphoretic speeds of the same sols have been obtained by the transport apparatus of Engel and Pauli and the results are also reproducible within about 2%. The results of the moving boundary method have been found to agree with those of the transport method-almost within the range of experimental accuracy