Patent GB-653472-A (GB)
Title: An automatic apparatus for controlling and recording the distillation of a liquid
IPC: G01N25/14
Filed: 1948-07-21
Abstract: <PICT:0653472/III/1> Automatic apparatus for controlling and recording the distillation of a liquid comprises a flask 10 (Fig. 5) and transparent receiver 32 interconnected by a condenser 20, a thermocouple 13 in the flask, a photo-electric cell responsive to the change of volume of the distillate in the receiver, a timing motor, and a potentiometer responsive to the photo-electric and timing effect for varying the current supply to a heater 28 for the flask, and a drum 77 on which is recorded the temperature volume curve of the liquid.  Mounted across the receiving graduate 32 are two photo-cell units 54, 55 and 68, 69 (Fig. 2), the first being responsive to the first drop of distillate and the second to the meniscus level of the distillate in the flask.  The second photo-cell unit is mounted on a worm gear 58 operated by a motor 57 while the first photo-cell unit is fixed.  The photo-cell units and graduates are rotatable about a rod 36, when the current is switched on to the heater 28 and a timing motor is also set in p  operation.  After two minutes a solenoid 43 is momentarily energized by means of a second timing motor thereby revolving the photo-cell assemblies and graduate in an anti-clockwise direction about rod 36 so that a pen 74 mounted on the second photo-cell unit contacts the graph paper on the cylinder 77, thereby making a mark.  The assembly then returns to its initial position until the first drop of distillate <PICT:0653472/III/2> <PICT:0653472/III/3> appears.  As the first drop passes the photo-cell 54, 55 and intercepts the light beam, the relay 43 is adapted to be again actuated and the assembly again moves in an anti-clockwise direction so as to position the pen on the graph once more and to move the graduate so that the distillate runs down the side and the meniscus rises steadily with no disturbance.  Relay 43 now remains energized by means of a holding circuit.  As the distillate flows into the graduate the meniscus of the liquid intercepts the light beam of the second photo-cell unit 68, 69 thereby energizing motor 57 which repositions the photo-cell unit. The photo-cell unit, therefore, moves up in correspondence with the liquid level.  The thermocouple 13 is adapted to operate a motor 78 driving the drum 77 in one direction or the other according as the temperature exceeds or falls below a predetermined value so that a graph is obtained which is a continuous function of temperature and volume of distillate.  The second timing motor is adapted during the distillation to periodically actuate motor 57 so as to cause the pen 74 to jerk, thereby leaving time marks on the graph.  In order to ensure that the distillation is completed in a specified time, the heater current is controlled by a potentiometer assembly 107, 108 (Fig. 9).  A contact 110 is driven across the potentiometer 108 at a constant speed by the first timing motor while a contact 109 is driven across the potentiometer 107 by means of the second photo-cell unit 68, 69.  If the distillation rate deviates from the desired rate the contact 109 will lead or lag contact 110 and an out-of-balance voltage will be generated of phase and magnitude depending upon the direction and magnitude of the deviation.  This voltage is fed via the grids of an amplifier 202 and phase inverter 203 to two thyratrons 204, 205, the output of which controls the current to the heater.  The amplified out-of-balance voltage, therefore, varies the heater current in a sense to correct the deviation.  A fan 101 (Fig. 5) is adapted to circulate air around the condenser 20, cooling chamber 19 and the graduate 32 so as to keep the graduate at a substantially constant temperature.  A collar 165 (Fig. 2) on the photo-cell unit 68, 69 cooperates with collar 164 after the graduate is full to push vertically upwards a rod 160 having switch mechanism 166 which when actuated reverses motor 57 to return the photo-cell unit to the starting point.  Switch 166 is re-opened ready for the next distillation by co-operation of collar 165 with a second collar 163 on the rod 160.