516 Dr. Hofmann on the Metamorphoses of Indigo. 



of the equivalent of the electro-negative body bromine, the 

 basic properties of the original system is enfeebled ; substi- 

 tute now another equivalent of bromine for hydrogen, and we 

 have dibromaniline. The facility with which, as we men- 

 tioned, all its salts are decomposed, evidently indicates that 

 the basic character of aniline is further enfeebled by the re- 

 peated assumption of bromine. Finally, in tribromaniline the 

 electro-negative properties of the assumed bromine equiva- 

 lents have placed themselves in equilibrium with the electro- 

 positive character of the original system. Possibly, by the fur- 

 ther addition of bromine, a body may be formed possessing 

 acid properties. 



We have in inorganic chemistry the compounds of many 

 metals with oxygen which exhibit in a distant degree the 

 same character; for distant I must call it, since it is not a 

 question of substitution. Protoxide of manganese is a strong 

 base, whilst in the sesquioxide, richer in oxygen, the basic 

 properties are lessened ; peroxide of manganese unites with 

 neither base nor acid, and by the addition of more oxygen we 

 have manganic and hyper manganic acid generated. 



It is only with the greatest diffidence 1 venture to express 

 an opinion on this subject : nothing is more dangerous than 

 to wish to draw general conclusions without having a mass of 

 facts at command. 



Bromaniline and dibromaniline possess, though in a lesser 

 degree, the fundamental properties of aniline — they are bases. 

 Tribromaniline is neutral ; in it the original character of 

 aniline has entirely disappeared. This body was however 

 produced in a totally different way from that of the two bro- 

 minated bases. It may be objected, that in it the grouping of 

 the atoms, as they prevailed in the original system of aniline, 

 no longer remained. Possibly there may exist a body of the 



same composition having the formula C^^-l ^^ lj«j^ which 



still possesses basic properties. Such a body would be formed 



by distilling tribromisatine, C^q-1 gf r-N04, with hydrate 



of potash. This compound is as yet unknown. Further ex- 

 periments must therefore be made to solve the question. 



Before concluding this memoir I shall mention another com- 

 pound which appears worthy of the attention of chemists. 



It is formed by passing into aniline free from water a stream 

 of cyanic acid obtained by distilling cyanuric acid. The fluid 

 becomes considerably heated, and solidifies on cooling into a 

 crystalline mass. These crystals are insoluble in water, but 

 soluble in boiling alcohol, from which they are deposited in 



