Magnesium Bisulfite Hydrazine Hydrate

For the synthesis of magnesium bisulfite complex, an aqueous solution of MgCl2 is mixed with aqueous (N2H5)2S03-H20 or (N2H4)2-H2S03-H20 stoichiometrically in a Mg SO3 ratio of 1 2. The compound is precipitated out by addition of alcohol. It is further washed with alcohol, then diethyl ether and dried in vacuum desiccator [22]  

MgCl2+2(N2H4)2-H2S03H20 Mg(HS03)2N2H4H20 + HCl + N2H5CI + H2O + 2N2H4 

Interestingly, the same compound is obtained when synthesis is carried out with (N2H5)2S03 H20 in hydrazine hydrate instead of aqueous solution. 

Subsequently, hydrazine decomposes at around 190 °C with the evolution of N2 and NH3 gases, with a 41.5% weight loss observed in the TG curve for this step  

The TG profile further shows decomposition of the intermediate MgSiOs, magnesium thiosulfite, with a weight loss of 67.5% between 335 and 580 °C due to the formation of MgO and MgS04 by disproportionation as follows  

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