hydrosulphite

If added too quickly the hydrosulphite will cake, fall to the bottom and be difficult to dissolve.

It has many advantages over the hydrosulphite vat, as it is not nearly so much affected by changes of temperature and weather.

Of the other reducing agents which have been used, sodium hydrosulphite (Na2SO2) deserves mention.

This may most conveniently be done by adding thereto a solution of hydrosulphite of soda, which may be made by mixing 4½ lb.

This is dehydrated sodium hydrosulphite with the chemical formula, Na2S2O4.