128 PROCEEDINGS OP THE AMERICAN ACADEMY. 



gen under the action of sodic ethylate, but even with these we do not 

 feel that enough facts are known to make it possible to deduce a 

 general rule iu regard to the conditions, which produce this curious 

 reaction. The collection of such facts will be continued iu this 

 Laboratory. 



We also tried the action of fuming nitric acid on unsymmetrical tri- 

 bromiodbenzol, and found that iodine was set free, and the organic 

 product was the tribromdinitrobenzol melting at 192°, and having the 

 constitution Br.NOa.Br.NOa-Br.H. 



A few statistics which we have collected about the removal of radi- 

 cals from substituted benzols may be given here. By far the greater 

 number of such removals are tliose in which a negative radical stands 

 in the ortho position to the radical removed. Of these we have 

 counted over sixty cases, in only nine of which the negative radical is 

 a halogen. Of the cases of removal, where there is no negative radi- 

 cal in the ortho position, we have found four in which a negative radi- 

 cal is in the para position to the radical removed ; these are C^H^Brj, 

 CgH4ClN02, C^H^BrNOa, and C6H4(N02)2; and to these perhaps 

 should be added five of the nine cases mentioned above, in which the 

 ortho radical is a halogen, as in all of these there is a nitro group in 

 the para position to the radical removed.* In no case is a radical re- 

 moved which is only in the meta position to a single negative radical ; f 

 but if there are two negative radicals in meta positions to the radical 

 attached (symmetrical tri-compound), there are two cases in which 

 substitution has been observed, C^jHgBrg and CeH8(N02)3. 



Experimental Part. 

 J3ehavior of Tribromiodbenzol. 



The tribromiodbenzol (I 1, Br 2, Br 4, Br 6) was made from sym- 

 metrical tribromaniline by replacing the amido group by an atom of 

 iodine. Silberstein, J who discovered this substance, made it from the 

 nitrate of diazotribrombenzol. AVe have preferred to use the sulphate, 

 and, as our method seemed to give a better result than Silberstein's 



* In the other cases where a radical was removed, which was ortho only to 

 halogens, these halogens were in the diortho position, and therefore probably 

 were sufRcient to cause the removal. 



t The conversions of meta and para nitranisol into the corresponding nitran- 

 ilines were not counted, because they took place at such a high temperature, 

 200° ; but perhaps they should be added to the list given above. 



X Journ. Prakt. Chem., [2.], XXVII. 119. 



