with sodium sulfite. No improvement in the quality or quantity
of the product was obtained by using zinc and acetic acid.

It is best to use freshly prepared sodium sulfite for the reduction,
since the commercial quality is poor and gives a lower yield
of phenylhydrazine. A cylinder of liquid sulfur dioxide should,
of course, be available.

The rapid addition of the diazonium salt solution to the sodium
sulfite seems to be advantageous.

Pure phenylhydrazine dissolves in dilute acetic acid to yield
a perfectly clear solution.

The phenylhydrazine hydrochloride may be purified by crystallizing
from water. A 600-cc. portion of water is used for 100 g.
of crude hydrochloride, and the solution boiled a short time
with a few grams of animal charcoal. After filtering, 200 cc.
of concentrated hydrochloric acid are added, and the mixture cooled
to 0'0. Pure white crystals in a yield of 85-90 g. are obtained.

Rubber gloves should be worn when working with large quantities
of phenylhydrazine, since the product may cause serious injury
to the skin. The vapors of phenylhydrazine should not be inhaled.


3. Other Methods of Preparation

Phenylhydrazine has been prepared by the reduction of benzene diazonium
salts with sulfites;[1] by the reduction of benzene diazonium