Experimental study of precipitating systems; computerised analysis of the optical transmittance and associated noise

The change of the transmittance in a precipitant system has been measured b y using a focused laser beam into a precipitation cell in which the precipi tate was generated by an injection technique. We have monitored the evoluti on of the transmittance on several precipitation processes with different c hemicals (PbI2, PbSO4, BaSO4 and BaC2O4) and quantities of precipitated mas s (20.0, 17.5, 15.0, 12.5 and 10.0 mg). The noise associated to the transmi ttance signal has been obtained by a numerical procedure based on computer analysis, finding that it provides information about particle shape feature s and nucleation kinetics. (C) 2001 Elsevier Science Ltd. All rights reserv ed.