Modified Zirconium‐Alizarin Reagent for Determination of Fluoride in Water

Problems in Estimating Fluorides in Water

“…When distillation is used in the separation of interfering substances, precautions must be taken to prevent further errors resulting from the remedial procedure itself-volatile acids, the distillate can be caused by: [1] too high a distillation temperature, [2] too rapid a distillation rate, [3] overheating of the flask surface above the liquid level, or [4] improperly assembled equipment. Figure 1 illustrates the pronounced effect of low pH upon the fluoride readings.…”

“…Gravimetric and volumetric methods are either unavailable or unsuitable for general use. The more successful procedures are colorimetric methods based on the bleaching action of the fluoride ion on certain organo-metallic complexes (1)(2)(3)(4)(5)(6)(7)(8)(9) . In particular, the action of 573 fluoride on a zirconium-alizarin lake has been intensively investigated and appears to be the best method available at the present time.…”

Estimation of Flow‐Through Time by the Continuous‐Dose Method

“…The potassium permanganate created no density problem in the basin and allowed observation of the displacement at all stages of the run; furthermore, the potassium permanganate concentration of the effluent could be determined by colorimetric measurement of the characteristic purple color. The sodium fluoride was measured by the Megregian-Maier photometric pro- cedure (7). It was necessary, however, to decolorize the potassium permanganate in 100-ml sample with 1-3 drops of 0.1 N sodium thiosulfate in the presence of the zirconyl acid reagent before the final addition of the alizarin reagent.…”

Use of Fluoride as a Tracer in Distribution System Studies

“…To reduce analysis time, a 5-min qualitative test was developed, employing a modification of the zirconiumalizarin method described by Megregian and Maier (1). A 5-ml portion of the reagent was mixed rapidly with both the control and test samples of water.…”

“…In the equation: Factors which may render this analysis invalid, by varying A and d, are: [1] any major physical change in the distribution system which will either provide a new route to the point under study or will replace pipe in the route with pipe of a diameter different from the original; [2] a major change in the operating level of the reservoir; or [3] a major change in demand characteristics of the system. None of these factors is likely to invalidate the original data for some time, as such changes do not occur rapidly in a system.…”