1364980 Coated articles OMNIUM TECHNIQUE D'ADMINISTRATION ET DE GESTION O T A and L FACY 25 Feb 1972 8803172 Heading B2E [Also in Divisions G1 and G5] A model in relief of a macro-structure such as a building, aircraft, ship or geographical site is constructed of a substrate coated with a dried layer of an emulsion containing one or more indicators and having over the dried layer an outer covering which is transparent and semi-permeable. The emulsion may be gelatin-based. The semi-permeable material may comprise cadmium ferrocyanide or a plastics material such as nitro cellulose or collodion. The substrate may be coated by spraying a first coating of an emulsion at 40-45‹C of at least one indicator, spraying one or more further coatings of the emulsion on to the previously dried coatings, forming a covering of a transparent semi-permeable material over emulsion layer. In an embodiment the protective membrane is formed in situ by the inclusion of potassium ferrocyanide in the emulsion and spraying the emulsion layer with a solution of cadmium chloride. In another embodiment the membrane is applied by spraying a solution of the plastics material or collodion in acetone or propyl alcohol on to the emulsion layer. In the case of a plastics membrane the membrane coating may be further sprayed with a substance which dissolves the plastics material. The coated substrate may be a model used for determining the location of fluid pollutants in a particular geographical site. As shown in the figure a structure 1a is mounted between the walls of a chamber 2 having apertures which can be connected to a circuit supplying a return flow of liquid. The chamber also contains groups of adjustable shutters. honeycombe panel and a device comprising heated plates (not shown). The horizontal and vertical dimensions of surface 1 correspond on a suitable scale to the surface relief of a geographical site. The devices can be used to adjust or modify the flow of the stream into the chamber. The model is also formed with scaled-down chimneys or shafts 3. The model surface 1 is coated with coloured indicators, e.g. yellow butter and bromo cresol in gelatine after which the layer 4 is covered with a membrane of cadmium ferrocyanide or nitrocellulose and the model then placed in the chamber supplying the stream 2. Hydrochloric acid solution is injected into chamber 2 through shafts 3. A plume 6 forms at the outlet of each shaft 3, resulting from turbulent diffusion of the acid in the hydraulic stream. Small molecules, e.g. water molecules and hydroxonium ions and the ions in the stream can reach the butter yellow and the bromo cresol stream through membrane 5. The isoconcentration surfaces of plume 6 reach layers 5, 4 at places a, b, c thus producing surfaces ab, be on the model having different spectral colours depending on the ion concentration of those parts of the plume in contact with layer 4. The colours of the differenet parts of the model can be used to evaluate the concentration of pollutant which would occur on the ground at the site as the result of emission corresponding to that from a shaft or chimneys.
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