Determination of Fluorides in Natural Waters

Abstract

held rigid by a clamp. The small pitman has a hardened steel button which engages in a groove cut in one link of the shackle. At mid-position the button does not touch the link, whereas the cam action at both ends of the stroke causes the link to weave as it would on the road, because of the up and down motion of the springs.

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.…”

Fluoridation of Public Water Supplies

“…t Ref.14. of a zirconium-alizarin lake in an acid solution(9)(10)(11). In general, this reagent is relatively unstable, the color range is narrow, the color development requires about an hour, and many other ions in water interfere with the reading.…”

Methods of Testing and Significance of Fluorine and Fluorides in Water Supplies

“…The procedure of deBoer has been modified by Casares (7), Thompson and Taylor (8), Elvove (9), and the writer (10). In this method, use is made of the fact that, in an acid solution, fluorides cause a zirconium-alizarine mixture, or a solution of purpurin (1,2,4, trihydroxyanthraquinone) to change color from pink to yellow, the quantity of fluorine present being estimated by the amount of fading of the pink color.…”