first arcuate channel 153 and arcuate slot 154 vacuum pressure in the first region 147 and in the second air line 173 is relieved the mixing cell 57 is also no longer subject to vacuum pressure however the mixed orange juice is not dispensed because the third pneumatic valve 81 remains closed and as will be momentarily described the second pneumatic valve 79 also closes thus the orange juice is held in the mixing cell 81 pending the next activation of the dispenser 1 the end of the return stroke of the piston 119 also places the second arcuate channel 165 in the cylindrical tube 125 of the piston in registration with the o ring 161 of the divider 141 the second region 149 of the second cylinder 117 communicates with ambient pressure by way of the second arcuate channel 165 and the first passage 167 in the column the positive pressure in first air line 171 is also relieved to ambient the portion of the cover sheet 49 associated with the concentrate metering cell 53 may then return under its own resiliency to a relaxed position from a position abutting the tray 47 in the recess 47 a defining part of the concentrate metering cell a return to ambient pressure in the branch 83 of the first air line.