Total sulphurous acid determination in wine - for use in control of wine prodn

摘要

In the determination of total sulphurous acid in liquids, e.g. in white wine, by the known technique of making the test liquid alkaline for saponifying bound sulphurous acid, then mixing it with a predetermined excess of iodate soln, acidifying and after a predetermined time treating with iodide, the excess iodine formed then being back-titrated, the liquid is treated with starch before formation of iodine and the iodide addn. takes place directly after the appearance of the blue colour caused by iodine-starch formation. Esp. the starch is added together with the iodate soln., which may be in the form of an alkaline soln. containing sufficient alkali to make the test liquid alkaline.