controller 154 which in turn transmits signal 156 to motor 160 since motor 160 is of the variable speed type the signal 156 calls for the motor 160 to increase in speed which in turn will increase the flow of liquid through pump 621 to the point where the ratio of stream 10 and stream 20 is of the proper value when the flow of stream 10 decreases the control loop will reverse the procedure to reduce the speed of pump 621 to maintain a constant ratio between stream 10 and stream 20 the signal 150 is representative of the rate of flow through the conduit 56 and is established for example by a speed element 152 coupled to pump 621 for example where pump 621 is of the positive displacement type the signal 148 is received by the speed controller 154 which produces a suitable signal 156 which is relayed to the motor 160 coupled to the pump 621 thereby controlling the speed of the pump 621 and thus the flow rate of stream 20 in response to the flow rate on the stream 10 the invention is further illustrated by the following table showing calculated balances for a preferred embodiment with reference to fig1 b table i__________________________________________________________________________ streamcomponent sup 1 10 20 30 40 50 60__________________________________________________________________________ethylene 8856 1080 9936 9936 5285 3571polymer 360 000 109 968 469 968 469 968 360 000solvent sup 2 2 211 408 380 280 2 480 640 2 480 640 1 318 560 892 848wt polymer 13 95 28 92 15 87 15 87 28.