Considerable controversy arose as to the constitution of the salts of this acid, the formula of sodium salt, for example, being written as NaHSO 2 and Na 2 S 2 O 4; but the investigations of C. Bernthsen (Ann., 1881, 208, p. 142; 1882, 211, p. 285; Ber., 1900, 33, p. 126) seem to decide definitely in favour of the latter (see also T.
The acid sulphite, NaHSO 3, obtained by saturating a cold solution of the carbonate with sulphur dioxide and precipitating by alcohol, is employed for sterilizing beer casks.
The acid sulphate, NaHSO 4, also known as bisulphate of soda, is obtained as large asymmetric prisms by crystallizing a solution of equivalent quantities of the normal sulphate and sulphuric acid above 50°.
At first principally acid sodium sulphate, NaHSO 4, is formed together with some normal sulphate; later, when the temperature has risen, the NaHSO 4 acts with more NaC1 so that nearly all of it is converted into Na 2 SO 4.
Acid sodium sulphate, NaHSO 4, has been employed in the manufacture of sulphur trioxide.