GB817474A - Improvements in or relating to the analytical testing of liquids - Google Patents

Abstract

Water or other liquid may be tested for the presence of substances which cause hardness or for substances such as silica, phosphate, sugar, chlorine or ozone, by adding in a first measuring stage an indicator and possibly a buffer and adding in a second measuring stage a complexing agent such as nitrilo-triacetic acid or the disodium salt of an alkylene diamine tetraacetic acid, in constantly set amounts and measuring the shade of colour resulting in the two different stages as a quantitive means of determining the amount of substances in the liquids. In a continuous-working device, as shown in Fig. 1, the liquid to be tested flows <PICT:0817474/III/1> <PICT:0817474/III/2> from an overflow container 1 through a capillary tube 2 to mixing chamber 3 where an indicator 4 may be added. A tinted solution passing through a mixing pipe system 5 into the first measuring chamber 6. The photo-cell cell 8 records the depth of colour from the lamp 7 through colour filter 9. The tinted liquid now passes into the second mixing chamber 10, to which additional indicators or complexing agents may be added at 11, as in the first chamber, either as a solid or alternatively by means of drop capillaries. The liquid passes through another mixing pipe system 12 and reaches the second measuring chamber 13 where it is again subjected to lamp 7. The two photo-cells 8 and 15 are connected differentially and the differential current is indicated by the measuring instrument 17. Fig. 2 shows a method for intermittent working. Anthron is used as the indicator for sugar, tetra - methyl - 4,41 - diaminodiphenyl methane for ozone and chlorine.