Reactions of this type are carried out continuously in electrodialysis apparatus, which includes anion and cation exchange membranes of a particular succession. Bromide ion, included in NaBr, under the influence of electricity migrates to the gelatinous emulsion stream through the anion exchange membrane.
Silver ion migrates to the emulsion stream through the cation exchange membrane from the adjacent section with AgNO3. Thereby, the photographic emulsion AgBr, free from the extraneous electrolytes, in this apparatus is obtained continuously. NaNO3 electrolyte is formed in a separate section. Likewise, other exchange reactions can be carried out, such as obtaining NaOH and CaCl2 from NaCl and Ca(OH)2; KNO3 and NaCl from KCl and NaNO3 and others.