Date of Award
Bachelor of Science (BS)
F. D. Holland Jr
The purpose of the experiment herein reported is to establish whether or not a correlation exists between the settling velocities of the fine particles of sediments and the change in resistance to the flow of electricity through a fluid containing the sediments. It was assumed that the sediments would behave according to Stokes’ Law regarding the velocities of their settling, and the pipette method of analysis was used to measure the particle size with which to compare the results of measuring change of resistance.
The equipment used in measuring the change of resistance as the particles settled was a 1,000 ml. graduated cylinder, drilled and fitted with electrodes, and joined to an electrical circuit as one of the resistances of a Wheatstone Bridge. A decade box was used as a balancing resistance and the point of balance was determined with an oscilloscope. Filling the cylinder with distilled water and introducing the sediments caused an unbalance in the bridge which was balanced by the decade box and the amount of change was noted against time.
Before a satisfactory circuit was found for accomplishing the measurement just described, the order of magnitude of the resistance, the type of load caused by the fluid and the sediment, the effect of both alternating and direct current, the effect of addition of electrolytes into the fluid, the effect of variation of the chemical composition of the sediment, the effect on conductivity from allowing the sediment to remain in solution for five hours and later for two days, the effect on conductivity by increasing the amount of sediment, all had to be investigated. The report consists mainly of the results of these investigations. Further investigations than these are necessary to establish the nature of any correlation which may exist between particle size and electrical resistance.
The experiment points to the fact that solution activity is so great when sediments are introduced into water that the electrical properties of the sediment change in accordance to the rate of solubility, and that since this is true, other physical properties of sediments may be so greatly changed upon their introduction into solutions that any attempt to measure these properties may result in serious errors. Particle size is probably one of these properties.
Mikkelson, D. H., "Size Measurement of Fine Sediments By Electrical Resistance" (1956). Undergraduate Theses and Senior Projects. 10.