Viscosity Characteristics of Clays in Connection with Drilling Muds

For the past few years a great amount of work has been done on the viscositycharacteristics and gelation of clay suspensions, much of which has beenreported in papers published by the Institute. Important reviews have been madeelsewhere by Evans and Reid, Marshall and Clews, Macey and Rigby, the last twoon the general properties of clay. It is unnecessary, therefore, torecapitulate past work beyond recalling that three explanations for the highviscosity and gelation of clay suspensions have been put forward. For lack ofmore exact nomenclature, these may be called the water hull, mechanicalinterference and attraction-repulsion theories. The first pictures the clayparticles as surrounded by relatively rigid water envelopes, which increaseeffective volume; the second emphasizes the mechanical interference of platyparticles or their agglomerates; while in the third the particles are assumedto be held relatively rigidly at a distance from each other determined by thebalance between the attractive (van der Waal's) forces and the electricalrepulsions of the charges. This article presents fresh data on claysuspensions, particularly on the influence of previous flow history of thesuspensions, specific contra-ions, temperature, solvation and particle size, inan attempt to contribute to the solution of the problem. Experimental Procedure Preparation of Samples.-Suspensions of the raw clays were prepared by addingthe clay to water with vigorous stirring and allowing the mixture to stand forseveral hours. In bentonite suspensions, the sand that settled was removed.Many of the suspensions were put through a homogenizer for deflocculationbefore use. The suspensions containing alcohol and pyridine were prepared bygradually adding a known quantity of the C.P. reagent to the clay, shakingafter each addition. They were then allowed to stand for two days beforemeasurements were taken. All concentrations are expressed on a weight per centbasis. T.P. 1002