This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
Sodium bicarbonate.. 5 ounces
Alum.............. 5.5 ounces
Potassium bromide... 4 ounces Hydrochloric acid enough. Water enough to make 4 pints. To 3 parts of boiling water add the alum and then the bicarbonate. Introduce enough hydrochloric acid to dissolve the precipitate of aluminum hydrate which forms and then add the potassium bromide. Add enough water to bring the measure of the finished product up to 4 pints.