Oceanography

3. Reagents

1. Sulphanilamide solution

Prepared as for NO^-₂-N estimation

2. Diamine solution

Prepared as for NO₂-N estimation

3. Ammonium chloride solution (Buffer solution)

12.5gm of NH₄Cl in 500 ml distilled water

Cadium-copped reduction column

This column is prepared by using cadium filings. 25ml of 2N HCL is added to 50g of cadmium filings. Within a minute the cadium filings are rinsed with distilled water. 100ml of saturated cupric sulphate solution is added to the cadium filings and the contents are swirled until all copper is deposited. The total deposition of copper is also indicated by the disappearance of the blue colour of CuSO₄. The bottom of the cadium column is plugged with small piece of glass wool and copper turnings. The column is filled with the cadium filing along with distilled water. The cadium filings should not be allowed to dry at the time of filling up of the column. The cadium filings are carefully packed in the column to a maximum height of 15cm. Care should be exercised not to trap any air bubbles. After the preparation of column, it is flushed with 50ml of distilled water and 5 ml of buffer solution.