36 
attained an advanced stage of development. It dyes under 
the same conditions as indigo tin does; but while the latter 
dyes a dull dark blue, indigorubin dyes a fine purple shade. 
Dr. Schunck, who is an authority on these matters, is of 
opinion that if it could be obtained in quantity, it would 
be a most valuable addition to the colours now in use.”*) 
Since this has been written, Baeyer has succeeded in 
finding a method which to all probability will soon be 
employed for the manufacture of indigo-blue on a large 
scale. The starting point is from cinnamic acid, which 
occurs in nature, being found in Gum-benzoin, Styrax, 
Balsam of Peru, and a few other aromatic bodies. These 
sources would be, however, far too expensive, and the quan- 
tity obtained therefrom much too small to make use 
of them. Now Bertagnini found, as early as 1856, that this 
acid may be obtained artifically by heating benzaldehyde, or 
oil of bitter almonds, with acetyl chloride : 
C 6 H 5 .CHO + CHyCOCl = C 6 H 6 .C 2 H 2 .C0 2 H + HC1. 
Since that time several processes have been found for 
obtaining oil of bitter almonds from toluol and from benzoic 
acid. The first point to be settled was therefore to ascer- 
tain which is the cheapest and best method for preparing 
this compound, as well as acetyl chloride, which is produced 
by the action of phosphorus chloride on acetic acid. 
W. H. Perkin, F.B.S., has discovered another synthesis of 
cinnamic acid, which probably may also be of practical 
value. He obtained it by boiling benzaldehyde with acetic 
anhydride and sodium acetate. 
By the action of nitric acid on cinnamic acid we obtain 
orthonitro-cinnamic acid, C 6 H 4 (N0 2 )C 2 H 2 C0 2 H, which readily 
combines with two atoms of bromine to form dibromnitro- 
phenylpropionic acid. This compound, by the action of 
alkali, is transformed into orthonitro-phenylpropiolic acid : 
C 6 H 4 (N0 2 )C 2 H 2 Br 2 .C0 2 H + 2NaOH = 
C 6 H 4 (N0 2 )C 2 .C0 2 H + 2NaBr + 2H 2 0. 
* ft The Bise and Development of Organic Chemistry.” Manchester, 
Cornish. 
