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Investigation into Increasing the Precision of a Rotating Disk-Solution Technique for the Analysis of Silicates

Volume 23, Number 2 (April 1969) Page 111-115

Ondrick, C.W.; Suhr, N.H.; Medlin, J.H.


The precision of major-minor silicate analyses employing a rotating disk-solution technique may be improved upon by restricting the number of sparkings on each end of the counter electrode to no more than two times; and by placing a more rigid control on disk weight than presently supplied by the manufacturer, i.e., prior to sparking, weigh the disks and place them in weight categories with a range of no greater than 30 mg. Room temperature fluctuations of 5°F or less are enough to decrease precision of the analysis; therefore, in order to maintain maximum precision, a tighter control on room temperature is required. Changes in barometric pressure affect the precision of certain major and minor oxides, therefore, during periods of stable barometric pressure the precision of the analysis is at an optimum. Relative humidity in the range of 40%-60% and minor shifts in the optical alignment of the grating appears to have little effect on the precision of the analyses.