Chlorine and caustic soda are essential chemicals whose production is indispensable for downstream chemical processes. Due to the immense production volumes in a typical chlor-alkali plant, small deviations and errors in the individual production steps can mean large financial losses. For this reason, complete and accurate process monitoring is important. Precise monitoring of the starting materials shows its advantages during the preparation of the brine. With LiquiSonic (photo), the concentration of the sodium chloride solution can be precisely adjusted down to 0.1 m%. Maximum saturation prolongs the life of the membranes during electrolysis and saves energy during subsequent concentration of the NaOH solution. After electrolysis, the caustic soda still has to be freed from unwanted NaCl residues and then concentrated to the usual purity. With LiquiSonic, this process can also be monitored and controlled in real time. — SensoTech GmbH, Magdeburg–Barleben, Germany