Titration of Fluorine in Aqueous Solutions

Abstract

Fluorine may be titrated quantitatively with thorium nitrate (0.1 N) in an aqueous solution, instead of the 48 per cent ethyl alcohol solution recommended by Willard and Winter (4), by closely controlling the pH of the solution to be titrated. A pH of from 2.9 to 3.1 was found to be suitable, and is obtained by the use of monochloroacetic acid, half neutralized by sodium hydroxide. The end point is more definite in an aqueous solution than in a 48 per cent ethyl alcohol solution. When using a 48 per cent alcoholic solution and 0.1 N tho-

Microdetermination of Fluorine by Thorium Nitrate Titration

“…Willard and Winter method for determining fluorine (11) with the use of sodium alizarin sulfonate indicator as proposed by Armstrong (2) has been modified recently as follows: by Hoskins and Ferris (8) who introduced the use of a buffer of monochloroacetic acid; by Armstrong (1) who titrated fluoride in an aqueous solution rather than in an alcoholic solution, and used silver perchlorate to remove interfering chlorides; and by Churchill, Bridges,and Rowley (3) who eliminated the effect of phosphate by a double distillation. Rowley and Churchill (10) applied the aqueous titration to the determination of quantities of 1 to 50 mg. of fluorine. Eberz, Lamb, and Lachele (6) studied the titration in alcoholic solution of quantities of 100 to 150 micrograms of fluorine.…”

Electrolytic Preparation of Pure Basic Aluminum Fluorides

“…A Willard-Winter steam distillation apparatus (Willard and Winter, 1933), as modified by Huckaby et al (1947), was used to separate the fluoride from the other elements present. The Rowley-Churchill (1937) modification of the original Willard-Winter titration of the fluoride distillate was used to titrate the fluoride distillate.…”

Volumetric Determination of Thorium by High Frequency Titrimetry

“…The authors' work indicated that fluoride might be a suitable reagent for the high frequency titration. However, titrations of fluoride with standard thorium, using the conditions of Rowley and Churchill (10), gave titration curves with extreme curvature in the region of the equivalence point. It was impossible to locate the end point on precisely these curves.…”