Patent GB-850742-A (GB)
Title: Process for testing properties of flowing material stream
IPC: G01N21/79
Filed: 1957-12-23
Abstract: 850,742. Photo-electric titration control. INDUSTRIAL RAYON CORPORATION. Dec. 23, 1957 [Dec. 31, 1956], No. 39867/57. Class 40(3) [Also in Group XXXVI] In testing the properties of a flowing stream of material of a type which demonstrates sudden changes as a result of treatment, a sample stream is continuously withdrawn from the main stream and is treated in a series of identical cycles so that the instant in the treatment cycle at which the transition points occur is an indication of the properties of the stream. Fig. 3 shows the invention applied to determining and controlling the zinc sulphate and sulphuric acid content of a rayon spin bath solution. The solution under test passes along duct 60 and a sample to be tested is taken from the main stream by a constant delivery pump 66 which passes into a mixing chamber 68 after the sodium sulphate content has been measured and controlled in the specific gravity tester 65. The mixing chamber is also fed from a reservoir with a sodium hydroxide titrant solution which is supplied by a constant delivery pump 76 providing a minimum stream and a variable delivery pump the rate of output of which varies cyclically under the control of a programming device 80 in the manner shown in Fig. 4. The programme controller also sends a signal representing rate of delivery of the pump to sulphuric acid recorder 84 and zinc sulphate recorder 85. The potential existing between a platinum reference electrode 91 in the titrant and a platinumrhenium indicator electrode 96 situated in the mixed solution leaving the test chamber triggers a thyratron when the rapidly changing potential difference between the electrodes indicates that either the sulphuric acid or a zinc sulphate has been neutralized. The thyratron triggers a pulsing device which feeds a standard pulse to a selector relay 105 which directs it to one of recorders 84, 85 according to the output of the programme controller to record the rate of addition of the titrant at the instant the neutral point was reached as indicated by the output of the programme controller at that time. The attainment of the next transition point is indicated by a further pulse from the derivative amplifier which controls the other recorder. In addition the outputs of the programme controllers when the transition points are reached are used to control variable delivery pumps 124, 122 to control the rate of addition of zinc sulphate and sulphuric acid solution to the main stream. The Specification also describes a simplified arrangement in which a single titrant is added (Fig. 1 not shown) or two different titrants may be added separately. Fig. 2 shows a photoelectric arrangement for detecting the transition points. In this case an indicator which changes colour when titration is complete is added to the titrant. Light from a source 56 passes through a window in the duct leaving the mixing chamber and a filter 58 and is detected by photo-cell 57. The filter is of such a colour to absorb the light transmitted through the solution when the indicator has changed colour indicating the end point. Phenolphthalein, which changes from colourless to red with a change from an acid to an alkaline pH, in co-operation with blue filter is suggested.