In the preparation of the sodium hypochlorite solution it is quite
necessary that the mixture be kept cold and be alkaline to red
litmus paper at the end of the reaction, if good yields of hydrazine
are to be obtained.
Since iron is an anti-catalyzer, it is necesssary{sic} to use
distilled water throughout the process.
As a viscolizer, a substance such as starch, glycerol, glue or
gelatine may be used; the last, however, gives by far the
most satisfactory results.
In order to obtain a pure white hydrazine sulfate as the
first precipitate, it is necessary to cool the hydrazine solution
thoroughly and filter it twice before the sulfuric acid is added.
Moreover, the sulfuric acid must be added slowly and with stirring.
If these conditions are not followed, material containing
brown particles results.
The mother liquor obtained from the crystallized hydrazine
sulfate contains a small amount of hydrazine. If 200 g.
of copper sulfate are dissolved in water and added to 10 l.
of the filtrates from the above processes, a light-blue crystalline
precipitate of the double salt of copper sulfate and hydrazine
sulfate will be formed after ten hours. This salt, when suspended
in ten times its weight of distilled water and treated with hydrogen
sulfide, decomposes into copper sulfide and hydrazine sulfate.
After the copper salt has been filtered off, the solution
is concentrated until the hydrazine sulfate crystallizes.
The yield of product is small, so that it is hardly advisable
to undertake this recovery in the laboratory.
It is possible for one man, simultaneously evaporating six dishes
of the hydrazine mixture, to turn out from 20 to 25 runs in nine hours.
The time for the evaporation of a solution, such as is mentioned
in the experimental part, with a four-flame Bunsen burner, is two to
three hours; if the evaporation is carried out more slowly than this,
the yield of product is distinctly diminished.