106 
POPULAR SCIENCE REVIEW. 
CHEMISTRY. 
Aniline Blue. — The conversion of red into aniline blue, discovered some 
years since by MM. Girard and De Lair, two young chemists from M. 
Pelouze’s laborator}^ occupies at the present time a very prominent 
position in the chemistry of dyes. Indeed, a very considerable manufac- 
ture, based upon this transition, is being carried on in England by Messrs. 
Simpson, Maull, and Nicholson, and in France by MM. Renard, Brothers, 
of Lyons. Till recently but little was known concerning the chemical 
changes involved in this conversion ; but in a memoir lately communicated 
to the French Academy, the whole mystery has been philosophically 
unfolded by Dr. W. A. Hofmann ( Comptes Rendus , 6th July). The 
author finds that the process for the transformation consists in treating 
rosaniline at a high temperature by aniline in excess. The change is 
readily achieved by treating salts of rosaniline in the presence of aniline, 
or reciprocally by treating rosaniline with salts of aniline, ammonia being- 
in both cases given off. Several analyses of the hydrochlorate which had 
been supplied by Mr. Nicholson lead to the expression — 
C 38 H 33 N 3 C1+ 
This formula contains the history of aniline blue ; for not only does it 
point out its chemical character and the relation which it bears to rosani- 
line, but it most satisfactorily explains the change which takes place in 
the conversion of the red into aniline blue. The above formula may be 
fairly rendered as follows : — 
C 38 H 33 N 3 C1=C 30 H 10 (C 5 H s ) 3 N 3 HC1 
In other words, the substance is the hydrochlorate of triphenylic rosaniline. 
This being granted, the equation beneath affords us a most exact explana- 
tion of the entire process, thus : — 
Salt of rosaniline. Aniline. Salt of triphenylic rosaniline. Ammonia. 
CjoHj 9 N 3 ,HC1-J-^C^H^N=C 30 H 1 g (C c H 5 ) 3 N 3 ,H(3+3H^N 
Dr. Hofmann has succeeded, moreover, in obtaining the free base, by 
pouring a concentrated solution of the chloride in ammoniacal alcohol 
into water ; this substance is then separated in clots. Hydrobromate, 
hydriodate, nitrate, and sulphate have also been obtained by the action of 
the acids on the free base. The action of reducing agents on the triphe- 
nylic rosaniline and the methylic, ethylic, and amylic derivatives of the 
base have been described in the valuable memoir to which we have 
referred. 
Putrefaction. — M. Pasteur, in continuing his researches on this subject, 
has presented an essay to the Academy, in which he shows that this pro- 
cess is, like that of fermentation, brought about by the influence of two 
distinct sets of beings; — one set, including Monas crepusculum , and 
Bacterium termo , lives upon oxygen, which it replaces by carbonic acid ; 
