Decomposition and Analysis of Organic Compounds Containing Fluorine and Other Halogens J. F. MILLER', HERSCHEL HUNT, AND E. T. McBEE Department of Chemistry and Purdue Research Foundation, Purdue University, Lafayette, Ind.
A method was developed for the decomposition and subsequent analysis of organic compounds containing fluorine and other halogens. Decomposition is accomplished by reaction with sodium in liquid ammonia in a closed system at room temperature. The halogens following the decomposition are present a5 halide ions in a system permitting determination without further separation. Halogens, except fluorine, are determined by standard methods. The fluorine is determined as lead chlorofluoride using closely controlled conditions of temperature and chloride-ion concentration. The method is applicable to the routine analysis of solid, liquid, and gaseous substances.
E
over the open ends of the iron . pipes _ and fastened to the frame with bolts and wing nuts. Safety Equipment. Goggles, face mask, and rubber gloves are provided for general protection in handling the reaction tubes and liquid ammonia. An ammonia gas mask should be readily available.
XTEKSIVE investigations in the field of polyhalogenated organic compounds, especially those containing fluorine, led to a demand for a rapid routine method for the analysis of a large number of samples. The analysis of such materials may be divided into two distinct parts: decomposition of the sample, and determination of the halide ions. DECOMPOSITION OF THE ORGANIC COMPOUND
The methods described in the literature for the decomposition of halogenated organic compounds either give incomplete decomposition of the very stable highly halogenated compounds or require an undesirable amount of time. Excellent reviews of the literature are given by Elving and Ligett (1) and by Nichols and Olsen (4). The sodium and liquid-ammonia method of Vaughn and Nieuwland (6) is readily adaptable to routine analysis, but it does not completely decompose a high percentage of the polyhalo compounds. However, results obtained by this method indicated that it might be possible t o obtain complete decomposition using a higher temperature and longer reaction time. In the method here proposed, the reaction is conducted a t room temperature and reaction time may be varied according to the ease of decomposition of each particular sample. This is accomplished by the use of a sealed glass tube as a reaction container. REAGElYTS AND APPARATUS
Reagents. All chemicals employed are reagent grade or the highest purity obtainable. Reagents should be tested to ensure absence of halogens. Reaction Tubes. A 50-cm. length of 13- to 14-mm. Pyrex tubing, standard wall thickness, closed a t one end with a testtube seal, constitutes the reaction container. Because of the high internal pressure generated during reaction, tubes should be free of flaws. Agitation. The apparatus for holding and rotating the reaction tubes is shown in Figure 1. The machine consists'of a steel rack made to hold 60 tu6es and to rotat)e slorvly (12 r.p.m.) on an axle in such a manner that the reaction tubes t,urn end-overend. h 55-cm. (22-inch) length of '/2-inch I.P.S. iron pipe, closed a t one end, is used as a safety shield for the glass tube. h hole, 0.3 em. (0.125 inch) in diameter, is drilled about 2.5 cm. (1 inch) from the open end of the pipe to allow for escaping gases in case of failure of the glass tube. A cotton plug at the bottom and a short piece of 0.25-inch rubber tubing held in place by a spring clip a t the top prevent the glass t,ube from moving and breaking due to mechanical shock. -1metal plate is fitted 1 Present address, Mellon Institute of Industrial Research, University of Pittsburgh, Pittsburgh, Po.
DECOMPOSITION O F SAiMPLE
The manner of weighing samples depends upon the physical state. Gases and low-boiling liquids (
