GB887576A - An automatic titrator - Google Patents

Abstract

<PICT:0887576/III/1> In an automatic titrator comprising a motor-operated metering pump for liquid to be titrated, a titration vessel, a motor-operated metering burette, a detector, a programmer operating the pump and burette in dependence on a defined sequence and responsive to the detector signal, and means for indicating the amount of titration liquid employed at the end-point, said burette comprises two chambers connected by a diaphragm, one for the titration liquid and the other for an inert liquid such as an oil, the latter being connected to a piston cylinder whereby the titrating liquid can be drawn into and expelled from the first chamber. In the illustrated apparatus, the burette is formed in two parts 24, 25 separated by flexible diaphragm 26 and having chambers 27, 28 respectively for an inert liquid such as an oil, and for the titrant. A duct 36 connects chamber 27 to a piston chamber 37, having a piston 38 attached to rod 39, operated by motor 42 through a worm gear 41; a bore 43 in the rod which is closable by device 44 serves to vent chamber 37 when necessary. The titrant is supplied to the chamber 28 through channel 32, duct 29 and a bore in cock 31 by withdrawing the liquid from chamber 27, by raising the piston until the diaphragm is in contact with the left hand side of chamber 27, and discharged, after rotating cock 31, through said bore and duct and through channel 33. The cock is rotated as required by means of motor 34, the contacts 35 being closed by a cam disc above the cock, whereby the motor is de-energized when the bore is in the appropriate position. A further channel is provided in the right hand portion 24, to carry away liquid which is discharged around the cock, if the latter rises due to generation of excessive pressure. The position of the piston may be determined conventionally, e.g. by means of a photo-cell or by the tele-transmitter system illustrated at 45-48. The result may also be obtained by drop-counting. For metering the liquid to be titrated, a diaphragm pump (not shown) consisting of two portions each identical with the right hand part 24 of Fig. 2 is disclosed, each of which is connected to a pressure pump supplying the liquid to be titrated and discharges into the titration vessel, which is supplied with the requisite amount of liquid by passing liquid into one chamber until the diaphragm is pressed against the wall of the other chamber and then repeating this operation twice and collecting the two discharged volumes of liquid.