Determination of live clay in foundry greensand by sodium-selective electrode

The rapid determination of 'live' clay in greensand is an essential procedure for the efficient running of a foundry production line, since progressive calcination of the clay binder during casting affects mould competence and quality of finish. A new method fur assessing the active fraction of clay in foundry sand is described that is based on the response of an ion-selective electrode (ISE) to sodium ions liberated from the clay by ammonium ions. The method possesses advantages of speed and objectivity over the Methylene Blue titration method presently employed in foundries. Results appear to be unaffected by the presence of coal dust in greensand.