Determination of Halogens in Organic Compounds

Abstract

INCE 1923 when Fajans and Hassel (6) applied adsorption S indicators to the argentometric determination of inorganic halides, the use of these indicators for this purpose has become rather extensive (9, 10). I n the field of organic analysis, however, they have been used successfully only for semimicroanalyses. Bobranski and Sucharda (9,s) and later Hardy (7) using a 2-to 3-centigram sample for analysis burned it in an atmosphere of oxygen over a platinum catalyst. I n the case of chlorides and bromides the combustion gases were passed over barium carbonate and the resulting barium halide was titrated with silver nitrate using eosin or fluorescein as adsorption indicator. For iodides, a 40 per cent solution of sodium sulfite was used as the absorption liquid, and the iodide formed after removal of excess sulfite by barium carbonate was titrated with silver nitrate using eosin as an indicator. Holscher (8) burned the sample in an air stream and passed the combustion gases through a 5 per cent hydrogen peroxide solution. After buffering with sodium acetate, he titrated the halide formed using dichlorofluorescein or eosin as adsorption indicator.On a macroscale Bambach and Rider (1) found t h a t dichlorofluorescein could be used successfully in the case of inorganic halides and organic hydrochlorides in alcohol-water solutions. They suggested the possibility of applying this titration in conjunction with the Stepanow method of reduction to the determination of the halogen content of organic substances.In the work reported in this paper it was found that a combination of a modified Stepanow procedure and a subsequent titration with silver nitrate using adsorption indicators was a reliable and accurate method for determining the halogen content of a variety of organic halides. Experimental ProcedureThe procedure employed for the reduction of the organic halides was based upon the modification of the Stepanow method proposed by Cook and Cook (4). The amounts of sodium and alcohol employed were calculated from the empirical rules of Drogin and Rosanoff @), except for halogenated nitro compounds where the 150 per cent increase recommended b y Cook and Cook was used.A weighed sample of thoroughly desiccated organic halide (equivalent t o approximately 25 cc. of 0.1 N silver nitrate, except in cases of halogenated nitro compounds where an amount approximately equivalent to 10 cc. of silver nitrate was used in order to avoid too great dilution of the solution to be titrated) was placed in a 250-cc. Erlenmeyer fiask fitted with a reflux condenser, the constricted tip of which had been removed. In the case of solids the samples were weighed into small vials which were dropped into the Erlenmeyer flask. For the analysis of liquids, small vials were made by heating 6-mm. glass tubing until one end was sealed and pressing this end against a flat surface while soft. This tubin was then cut off at a length of 3 cm., resulting in a small vial wkch stood erect on the balance pan. During weighings the open end of the tube was close...

Argentometric Microdetermination of Organic Chlorine

“…This kind of procedure must be applied in order to avoid the faults of the Volhard method. This modification has been described by Feldmann and Powell (5) in a macrodetermination of halogens, but is not applicable as it stands on a micro scale. Simple calculation shows that in order to + 0.25 °Substances synthesized recently in authors laboratory and analyzed by Miss Meizvó for their carbon and hydrogen contents to confirm the purity.…”

“…7 82.9 89.3 81.6 80. 5 81. 4 83.1 86.4 103.0 prepared, the traces on both sides measured, and the ten resulting values averaged.…”

The fundamentals of fluorescence.

“…With rhodamine B, an increase in concentration or a decrease in temperature shifts the peaks of the bands to longer wave lengths. Table 1 shows the effect of increased concentration of rhodamine B on peak wave length of fluorescence in cellulose acetate films (5).…”

“…Thus fluorescent indicators may be used to indicate pH changes in solution in an analogous manner to other types of indicators which produce color changes in various hydrogen-ion concentration ranges. Fluorescent indicators, such as eosin, fluorescein, and dichlorofluorescein, have been used in precipitation titrations to indicate the end point by the appearance of an adsorbed color on the surface of the precipitate suspended in the solution (5).…”

Determination of Halogens in Organic Compounds

“…To determine chlorides, the solution was then titrated with 0.1 N silver nitrate, using 4 to 5 drops of a 1 per cent solution of dichlorofluorescein as an absorption indicator. Eosin was used as the indicator when bromides were determined (5,7).…”