1863.] 715 



is necessary to use hydriodic acid which is colourless, otherwise the 

 free iodine will slowly act upon the new product. It crystallizes in 

 prisms, having a green metallic lustre. It is more insoluble than the 

 hydrobromate. Its analysis has led to the formula 



C 27 H 24 N 4 ,HI. 



Acetate of Mauveine. This salt is best obtained by dissolving 

 the base in boiling alcohol and acetic acid. It is a beautiful salt, 

 crystallizing in prisms possessing the green metallic lustre common 

 to most of the salts of mauveine. Combinations of this substance 

 gave numbers agreeing with the formula 



C 21 H 21 N 4 ,C 2 H 4 2 . 



Carbonate of Mauveine. The tendency of mauveine to combine 

 with carbonic acid is rather remarkable. If a quantity of its alco- 

 holic solution be thrown up into a tube containing carbonic acid 

 over mercury, the carbonic acid will be quickly absorbed. To 

 prepare the carbonate, it is necessary to pass carbonic acid gas 

 through boiling alcohol containing a quantity of mauveine in suspen- 

 sion ; it is then filtered quickly, and carbonic acid passed through 

 the filtrate until cold ; on standing, the carbonate will be deposited 

 as prisms having a green metallic lustre. This salt, on being dried, 

 gradually loses carbonic acid. From experiments that have been 

 made with this salt, it would appear to have the composition of an 



acid carbonate, viz. 



C 27 H 21 N 4 ,H 2 C0 3 . 



In the analysis of salts of mauveine great care has to be taken in 

 drying them thoroughly, as most of them are highly hygroscopic. 



I am now engaged with the study of the replaceable hydrogen in 

 mauveine, which I hope will throw some light upon its constitution. 

 From its formula, I believe it to be a tetramine, although up to the 

 present I have not obtained any definite salts with more than one 

 equivalent of acid. Mauveine, when heated with aniline, produces 

 a blue colouring matter, which is now under investigation. A salt 

 of mauveine, when heated alone, also produces a violet or blue 

 compound. 



