1. The effect of nickelous sulfate and hydrazine on thickness and appearance of electroless tin coatings were studies by electrochemical methods.

2. Qualified nickelous, sulfate, nickelous nitrate and nikel monoxide were prepared with waste raney nickel catalyst as raw material.

3. After decomposition with potassium chlorate and aqua regia as well as applying nickelous nitrate as basic body improving agent, the ashing temperature is increased.

4. The invention relates to a nickel sulfamate electroplating solution which comprises nickel sulfamate, boric acid and nickelous chloride.

5. The preparation principle, synthetic method and the optimum processing of nickelous hydrazine nitrate is displayed.

6. It is an new kind of method to make nickelous chloride solution and produce nickel powder by membrane electrolysis at the same time.