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Chemistry. — “On the preparation of pure o-toluidine and a 
method for ascertaining its purity.” By Prof. A. F. HoLLeMan. 
(Communicated in the meeting of November 26, 1904). 
Whilst p-toluidine being a solid, well crystallised substance may 
be very readily obtained in a perfectly pure state from the commer- 
cial product by recrystallisation and distillation, this is by no means 
the case with the liquid ortho-toluidine. The latter stands a good 
chance of containing its para-isomer as it is prepared from o-nitro- 
toluene, which is rather difficult to completely separate from the 
p-nitrotoluene simultaneously formed in the nitration of toluene, 
particularly because the ortho-nitrocompound is liquid. It is further 
stated that o-toluidine sometimes contains aniline. 
Of the various ways mentioned in the literature on the subject 
for the purification of o-toluidine, the conversion into oxalate seemed 
to me the most appropriate. According to Brmstrms Handbuch, the 
solubility of ortho-toluidine oxalate amounts to 2.38 parts by weight 
in 100 parts of water at 21°; that of the acid oxalate of p-toluidine 
(the neutral compound does not exist) 0.87 parts in 100 parts of 
water at 10°. If, therefore, the o-toluidine contains a few per cent 
of para, the oxalate thereof must remain in the aqueous mother- 
liquor when the mixture is submitted to recrystallisation, and the 
use of ether, which is given as an accurate method of separating 
the oxalates, becomes superfluous. Even any aniline which happens 
to be present, may be removed in this manner. 
In order to see whether a complete purification might indeed be 
attained in this way, it was necessary to first obtain a characteristic 
test for ascertaining the purity; for the processes found in the 
literature for ascertaining the purity of o-toluidine, of HÄUssERMANN 
(Fr. 26,750), Remuarr (Fr. 33,90) and Luner (Fr. 24,459) appeared 
but little suitable for the detection of very small amounts of impurities. 
For this purpose the determination of the solidifying point of the 
acetyl compound proved serviceable. By determining a portion of the 
solidifying point curve of o- and p-acetotoluidide the amount of the 
impurity could then be ascertained quantitatively at the same time. 
The following solidifying point figures were found : 
Percentage Solidifying 
of para. point. 
0 109.715 
1.12 108. 45 
2.42 107. 75 
9.58 103.°2 
13.6 100.°8 
