Theoretical study of the morphologically originated noise associated with the transmittance of a precipitation system.

In this paper we present the results of a computational study that analyses the relationship between the noise associated with the optical transmittance of a system of particles and the morphology of such particles. Computational algorithms have been developed in order to represent the different morphologies within a wide range of sizes. By using this methodology, it has been possible to study the morphology of particles in a virtual system, therefore avoiding the distortions that would inevitably be present in a real system. As a consequence of this study, a classification of the morphologies observed has been made according to the amount of noise they would add to the transmittance of a system of particles. The theoretical results obtained are in good agreement with the available experimental data obtained in real systems.

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 by using a focused laser beam into a precipitation cell in which the precipitate was generated by an injection technique. We have monitored the evolution of the transmittance on several precipitation processes with different chemicals (PbI2, PbSO4, BaSO4 and BaC2O4) and quantities of precipitated mass (20.0, 17.5, 15.0, 12.5 and 10.0 mg). The noise associated to the transmittance signal has been obtained by a numerical procedure based on computer analysis, finding that it provides information about particle shape features and nucleation kinetics.

Study of precipitant systems by computerised simulation. Influence of optical elements on the noise associated with the transmittance.

The transmittance signal of a precipitant system measured with a focused laser beam carries associated noise coming from several sources. In this work, we have studied the influence of the focal parameters (wavelength, focal length and prefocused radius of the beam) on the maximum noise reached in equivalent nucleation processes. For this purpose, a simulation program of precipitating systems, designed in FORTRAN 90, has been developed. The program generates simulated transmittances, which are processed by another computer program to extract associated noise. Wide ranges of values of the focal parameters have been analysed, finding relationships between the maximum noise and the focal parameters. They have been justified in connection with the changes observed in the radial parameters, which define the size and shape of the focused path.