JACKSON AND BEHR. SYMMETRICAL TRIIODBENZOL. 335 



tate which had formed; the filtrate was allowed to stand for several 

 hours, when it deposited a flocculent buff-colored precipitate, the weight 

 of which varied from 10 to 20 grams in different operations ; that is, 20 to 

 40 per cent of the theoretical yield. An additional amount of the triiod- 

 aniline could undoubtedly have been obtained from the black precipitate, 

 which was filtered out at first, but this was so impure that it seemed 

 more time would be lost in purifying it than in preparing fresh quanti- 

 ties of the second buff-colored precipitate, which without further treat- 

 ment was pure enough for the manufacture of the triiodbenzol. That it 

 was the triiodaniline was shown by an analysis of the substance purified 

 by crystallization from glacial acetic acid and alcohol with the aid of 

 boneblack* which gave 81.25 per cent of iodine instead of the 80.87 per 

 cent required by the formula. Its melting point was 185°. Michael and 

 Norton give 1 85|° . 



The monochloride of iodine used in this work was made by the action 

 of chlorine on iodine according to one of the methods given by Hannay,* 

 and used later by Bornemann.f Bunsen's $ method, which consists in 

 boiling iodine with aqua regia, gave a less good result. Distillation of 

 iodine with potassic chlorate, recommended by Schutzenberger § and 

 Hannay,|| was not tried. Forty-two grams of powdered iodine (the amount 

 needed for ten grams of aniline) were treated with dry chlorine in a flask, 

 until they had gained 12 grams; in addition to the reddish brown liquid 

 monochloride a considerable amount of the brilliant yellow crystalline 

 trichloride of iodine was formed, which was converted into the mono- 

 chloride by adding a small excess of iodine and heating the flask gently 

 on the steam bath under a short air condenser, until the yellow crystals 

 had disappeared. The monochloride of iodine solidified in fine gray 

 crystals, if cooled below 10°, and in this solid state could be kept for 

 some time without decomposition. Its tendency to solidify made it 

 necessary in the preparation of triiodaniline to use the solution of chloride 

 of aniline at a temperature of at least 15° in order to avoid the danger 

 of having the tube stopped up with monochloride of iodine. Although 

 this substance melts at 24°. 7 (Hannay), we found no trouble from solidi- 

 fication with a solution at 15°, which can be explained by the marked 

 tendency of the monochloride to remain liquid after it has been melted. 



* Proc. Lond. Chem. Soc., XXVI. 815 (1873). 



t Ann. Chem. (Liebig), CLXXXIX. 184 (1877). 



t Gmelin-Kraut's Handbuch, I. 2, p. 416. 



§ Zeitschr. d. Chem., VI. 1. 



II Proc. Lond. Chem. Soc, XXVI. 815 (1873). 



