COLORIMETRICAL PROCESS AND APPARATUS FOR DETERMINING CONTAMINATION OF ALUMINIUM HYDRATES

摘要

Continuous monitoring of the impurity content in a product travelling past in bulk and with a nonuniform thickness on a conveyor belt. The monitored impurity giving a colour reaction with a suitable reagent. …The invention consists of the combination of three means: … …  - a means for levelling the upper surface of the product on the belt at least in a certain region, …  - a means for spraying the reagent on the surface of the product which is thus levelled, in order to develop the colour by reaction with the impurity …  - a means for colorimetric determination of the intensity of the colour obtained with the aid of the reagent. … …The invention applies in particular to the monitoring of the residual sodium hydroxide content in alumina trihydrate obtained in the Bayer process before it is calcined. ……