33G PROCEEDINGS OF THE AMERICAN ACADEMY. 



Symmetrical Triiodbenzol, C 6 II 3 I 3 . 



This substance was prepared as follows: Ten grams of the buff- 

 colored triiodauilinc, made as described in the previous section, were 

 boiled with 125 c.c, of benzol and 25 c.c. of alcohol, and disregarding 

 the undissolved portion, 5 c.c. of commercial sulphuric acid were added. 

 and then 5 grams of finely powdered sodic nitrite were sifted into the 

 liquid as quickly as possible. As soon a- the evolution of nitrogen had 

 slackened sufficiently, the liquid was boiled for some time on the steam 

 hath, until a large part of the solvents had jtassed off; during this boil- 

 ing a bright yellow solid, which formed on the particles of sodic nitrite 

 as they eutered the liquid, changed its color to a light grayish brown. 

 After the solution had been boiled, it was allowed to stand over night, 

 and then the deposit was filtered out and washed, first with alcohol and 

 afterwards with hot water, to remove the inorganic salts. The amount 

 of this crude product rarely fell below 50 per cent of the theoretical yield. 



The product, obtained as described above, was next sublimed from a 

 large watch-glass heated on the sand bath, and covered with a funnel 

 which stood on a piece of filter paper above the substance. If this sub- 

 limation was carried on slowly enough, as much as so p. r cent of white 

 glistening crystals was obtained, but if it was urged too fast, the impuri- 

 ties also sublimed, and the crystals were yellow, or even in extreme 

 cases light brown and sticky. When proper care was used, white 

 crystals were obtained by this sublimation, even from verj impure 

 products, such as those recovered by evaporating the liquid portion of the 

 product of the diazo reaction. The white sublimed crystals were not, 

 however, pure, and to remove from them a persistent impurity we found 

 repeated recrystallizations from alcohol were necessary, which finally 

 raised the melting point to 181°, where it remained constant. The bud- 

 stance was then dried at 100°, and anal\ zed with the following results : — 



I. 0.1187 gram of the substance gave bj the method of Carius 0.1838 



gram of argentic iodide. 

 II. 0.1453 gram gave 0.2249 gram of argentic iodide. 



Calculated f<>r 1 oand, 



I H i I. II. 



Iodine ,l 83.f»C 83.G0 



Properties of 1 .3.5 Triiodbenzol. — This substance crystallizes from 

 alcohol at first in radiating groups composed of a few slender prisms, 

 which develop later into long white prisms frequently tapering, but 



