490 Canadian Record of Science. 
obtained, and its apparent unimportance, has received until 
lately no attention whatever. These two bases were long 
regarded merely as chemical curiosities whose chemical 
relations were of importance only so far as their existence 
threw light on other reactions, and thus aided general- 
ization. A few years ago, however, Greiss' announced that 
benzidin, like anilin, formed a diazo compound on treatment 
with nitrous acid. From this Gustav Schultz, of Berlin, in 
1879, prepared the first of the now important class of dyes 
called Azo-dyes from Benzidin, but the first economic dye 
of this class was patented in 1884 and named Congo red. 
These dyes, now very numerous, owe their importance in the 
arts to the fact that they dye wood and cotton fibre directly, 
1.€., without the use of a mordant. 
The success of the Congo red and other dyes of this class 
lead to the preparation of these rare bases, Benzidin and 
Tolidin, in available quantity. Through the kindness of 
Prof. Hofmann I was enabled to obtain from Gustav 
Schultz, of the Berlin anilin factory, a kilogramme of 
crude Tolidin, and began the study of its derivatives in 
Berlin three years ago. Some of these compounds have 
already been described by me, and formed part of a paper 
read before the British Association in 1886,’ but others have 
been obtained since. This paper deals chiefly with those 
derivatives obtained directly from the base Tolidin, and 
includes only those secondary derivatives necesary to 
illustrate completely a particularly reaction of the base 
itself. The subject is, however, by no means worked out as 
in a direction indicated at the end of this paper, it gives 
promise of interesting results yet to be obtained. © 
The crude base obtained from the factory proved to be 
the ortho-tolidin, and on purification crystallized in glisten- 
ing scales of a pale violet hue, melting at 128° C—not at 
112°, as was originally stated by Petriew.’ It turns in- 
tensely blue when treated with oxidizing agents, gives a 
! Journal fiir practische Chemie, 101, 92, 
2 Proc. Brit. Ass’n., 1886. 
3 Loc cit. 
