WHICH NITROGEN IS SUBSTITUTED EOR HYDROGEN. 
671 
I. 0’605 grm. of the compound, treated as above, gave 80 '4 cub. centims. of nitrogen 
at 0°, and 760 millims. bar. pressure = 0T01 grm. of nitrogen, or 16-70 per cent. 
Theory. Experiment. 
N=16-77 16-70 
II. -492 grm. of substance, dissolved in water and boiled, required for neutralization 
29-5 cub. centims. of alkali solution, corresponding to 0-185 grm. of nitric acid, or 37*77 
per cent. 
Calculated. Found. 
/ ^ , 
9 6 H 4 N 2 190 62-27 
NH9 3 63 37-73 37-77 
253 100-00 
Sulphate of Diazobenzol, € 6 H 4 N 2 , SH 2 0 4 . 
Acid sulphate of aniline, when Treated with nitrous acid, is converted into sulphate of 
diazobenzol according to the equation 
/ / 
*G 6 H 7 N, SH 2 O 4 +NH0 2 =€ 6 H 4 N 2 , SH 2 0 4 +2H 2 0. 
Acid sulphate Sulphate of diazobenzol. 
of aniline. 
On account of the slight solubility of sulphate of aniline, and in order to avoid 
employing a large quantity of liquid, it becomes necessary to suspend the salt in water, 
and to expose it in this state to the action of nitrous acid. The reaction, however, is 
very slow, and the salt is only gradually converted into the diazo-compound. I found 
it therefore more convenient to prepare the sulphate from the nitrate of diazobenzol, 
by treating a concentrated aqueous solution f of the latter with a sufficient quantity of 
sulphuric acid, previously diluted to avoid rise of temperature upon addition. 
The solution thus obtained is then mixed with three times its volume of absolute 
alcohol, and lastly with a sufficient amount of ether, which causes the sulphate of 
diazobenzol, together with some water, to separate in a layer at the bottom of the vessel, 
the liberated nitric acid, together with the excess of sulphuric acid, remaining mixed with 
the supernatant alcohol and ether. This latter is decanted, and the solution of the sul- 
phate (with a view to the removal of a further quantity of water) is once more treated 
with absolute alcohol and reprecipitated by means of ether. The precipitated liquid is 
then placed in flat dishes over sulphuric acid, when it soon solidifies to a magma of 
white crystals. In order to purify these crystals completely, they are washed on a filter 
with a mixture of alcohol and ether, which removes any trace of sulphuric and carbolic 
acids which may have been produced by a partial decomposition of the sulphate of 
diazobenzol, then dissolved in weak’ cold alcohol, and precipitated by the addition of 
* Ordinary sulphate of aniline containing excess of free sulphuric acid is understood by this formula, 
t The crude solution obtained by the action of nitrous acid upon nitrate of aniline may be employed. 
