the ten-month period was calculated by combining the separate sets.The standard deviations on triplicate analyses obtained during this long test period are summarized in Table IV. The testing was done on clear solutions of supersaturated and saturated liquor, as well as on slurries containing suspended red mud, whose liquid phase had a composition corresponding to supersaturated solution. These precisions are much better than those we have been able to obtain by the Watts-Utley procedure. For hydroxide it is about three times better, and for alumina it is about two times better.Application of Method. Apart from the usual saturated and supersaturated Bayer solutions, there are other solutions used in the Bayer plant, in which the concentrations of hydroxide and alumina vary over wide ranges. To show that the thermometric titration procedure was indeed suitable for the accurate determination of these levels, the experiments partially summarized in Table V were carried out. Solutions of known composition were prepared by dilution of a master solution into which was dissolved high purity alumina. The difference between the calculated concentrations of these solutions and the results found by the thermometric procedure was taken as the accuracy of the method. Thermometric titrations gave satisfactory accuracy over the entire range of concentrations that are encountered in a Bayer Process plant, from 10 to 600 grams per liter of hydroxide and from 3 to 120 grams per liter of alumina.
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