16 
May 7th. —Mr. J. F. Walker, M. A., F. C. S., then read a 
paper, illustrated with diagrams, on The Modifications of the 
Substitutions of Benzol.” He gave a short account of Professor 
Kekule’s theory of the constitution of this substance, and ex¬ 
plained how only three modifications of the compound formed 
were possible, when two atoms of hydrogen were replaced by 
two atoms of another element or by two radicals. He next 
gave the results of a series of experiments made by himself and 
Dr. Zincke. A large quantity of pure hrombenzol was prepared, 
and converted into mononitrobromhenzol by the action of nitric 
acid. Two modifications are formed; the one 'svhich melts at 
125 deg. C. is obtained in large quantities, and a small quantity 
of a modification which melts at 37 deg. C. Several attempts 
were made to increase the quantity of the latter by using acid 
of different strength and at various temperatures. It appeared 
that acid of sp. gr. 1‘5 at the temperature of a water hath gave 
the best results, but a large amount was never obtained. The 
first or ortho-nitrohromhenzol is less soluble in alcohol than the 
latter or meta-nitrobrombenzol, and they were separated by 
repeated re-crystallizations. A long research was made to see 
wdiether these two modifications gave, when converted into 
dinitrobrombenzol by means of a mixture of strong nitric and 
sulphuric acids, the same modification. A series of experiments 
were made, and it was found that both these modifications of 
mononitrobromhenzol (ortho and meta) gave the same dinitro- 
hrombenzol, which melted at 12 deg. C., which may be therefore 
called ortho-meta-dinitrobromhenzol. Both the modifications 
of mononitrobromhenzol were heated in sealed tubes to about 
180 deg. C. with a concentrated solution of alcoholic ammonia 
for ten to fifteen hours. The liquid was evaporated to dryness, 
and the residue crystallized out of boiling water. The ortho¬ 
modification gave a nitranilin identical with that obtained by 
Hofmann from acetanilid, which crystallizes out of boiling water 
in yellow needles, which melt at 146 deg. C. and can be sub¬ 
limed. The meta-mononitrobrombenzol gave a nitranilin whicli 
differed from the two known modifications in its solubility, 
melting point, and colour of its salts. It is far more soluble in 
water and in alcohol; its solution is an intense yellow colour 
and stains the skin, but not permanenlly. It is much more 
