An Apparatus for the Preparation of Tellurium Tetrachloride JOHN F. SUlTLE and ROBERT P. GECKLER Indiana University, Bloomington, Indiana THE preparation of organo-tellurium compounds 1Ntellunum . tetrachloride is often used as the source of tellurium. One of the simplest preparations of tellurium tetrachloride involves the direct chlorination of elemental tellurium;' however, in the preparation and preservation of an easily hydrolyzable substance like tellurium tetrachloride a great deal of care must be taken in the apparatus and technique used. The apparatus described below is made completely of pyrex glass and can be made by anyone with a little experience in glass blowing and the proper equipment. In a typical run, 85 grams of oven-dried tellurium (suitable tellurium may be made by reduction of a hydrochloric acid solution of tellurium dioxide with sulfur dioxide) is placed in a previously dried 500 m1.distillation flask The 24/40 3 joint is greased and then closed. The apparatus is now evacuated, and whiie connected to the source of vacuum, is carefully heated by means of a Bunsen burner to dry further the tellurium and the apparatus. Chlorine is introduced
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' SIMONS,J. H., "The properties of
I.Am. Chem. Soc., 52,3488 (1930).
tellurium tetrachloride,"
at a moderate rate after the evacuated system is shut off from its source of vacuum. A few drops of onitrotoluene is placed on the surface of the mercury in the manometer to protect it from the chlorine; however, by only occasional use of the manometer through manipulation of stopcock B the use of an inert liquid on the surface of t h e mercury may be avoided. The same liquid was used in the bubbler indicating qualitatively the flow of chlorine. The application of heat to the tellurium is unnecessary until the reaction mixture liquefies. In about two hours liquefaction of the reaction mixture to a black liquid begins. The inside pressure is approximately atmospheric by then. The introduction of the chlorine is continued and stopcock A is opened to allow any excess of chlorine to be absorbed by the sodium hydroxide solution. Until an excess of chlorine has been added the liquid and its vapor will be very dark brown or black due to the presence of tellurium dichloride. During the final part of the reaction when the mixture is liquid in character, the flame from a Bunsen burner is gently applied to the reaction flask.
When the liquid becomes amber in color the introduction of the chlorine is stopped. The system is evacuated again and allowed to remain on the vacuum line. The application of heat is carefully continued until enough of the liquid has distilled over to fill the first ampule two-thirds full. The ampule is then sealed off. During this distillation the material will tend to solidify in the 25-mm. tube to which the ampules are attached and must be melted frequently in order to facilitate flow of the
product into the ampules. The succeeding ampules are filled and removed the same way. Tellurium tetrachloride does not interfere with the working of the glass, so little difficulty is encountered in making the seals. From this run, nine sealed ampules each containing between 15 to 20 grams of tellurium tetrachloride can be obtained. The tellurium tetrachloride will remain stable a t room temperature in the sealed ampules.
