HYDRAZINE SULPHATE. 159
thus formed breaks down with water, essentially into sulphur dioxide, carbon
dioxide, and hydrazine sulphate:
H.N
I ^ C(SO 3 H) 2 + H 2 O = (H 2 N.NHa)H£O 4 + CO 2 + 2 SO,.Saturate a solution of 75 g. potassium hydroxide in 300 c.c. of
water with sulphur dioxide. To the solution of potassium bisul-
phite thus prepared add 50 g. of powdered potassium cyanide
(98-99%) while shaking; the yellow color of the bisulphite sol-
ution disappears, and the mixture becomes somewhat heated.
After all the cyanide has dissolved, heat the solution on the water
bath, and when, after some time, the liquid has become alkaline,
acidify it cautiously with hydrochloric acid. Repeat the cautious
additions of hydrochloric acid until the solution has become
permanently acid. This operation requires from 1.5 to 2 hours,
and in all about 30 c.c. of concentrated hydrochloric acid are
necessary. Finally, add an additional 150 c.c. of concentrated
hydrochloric acid and allow the mixture to stand in the ice-chest,
when 60 to 80 g. of the crystals of acid potassium aminomethane-
disulphonate are obtained. Collect this product on a filter and
wash it with water.
Treat this salt in separate portions of 23 g. each as follows:
stir each portion to a paste with 34 c.c. of water and then add to
it a solution of 10 g. potassium nitrite in 6 c.c. water. The tem-
perature of the mixture rises slowly to 40°-50° and within 10 or
15 minutes all of the solid salt has passed into solution. Make the
solution alkaline with a little caustic potash and allow it to cool;
about 18 g. of potassium diazomethanedisulphonate are deposited
from each portion in the form of orange-yellow needles.
Dissolve the latter salt in a solution of an equal weight of
crystallized sodium sulphite in two-thirds as much water; make
the solution alkaline by the addition of a little sodium carbonate
solution and then warm slightly until the color has disappeared.
Finally, decompose the salt of the trisulphonic acid by adding an
amount of 20% sulphuric acid equal to five times the weight of
the salt. When the liquid no longer smells of sulphur dioxide,
filter it and allow it to cool, whereby the hydrazine sulphate
crystallizes out. Obtain a further yield from the mother-liquor
and recrystallize the entire crude product from water. Yield,