Importance

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Abstract

A metering apparatus including a metering pump having a vertical, elongate pump cylinder tapered at one end to a point, and a piston arranged for axial movement in said cylinder, facilitates transfer of an accurately determined volume of liquid from a first vessel to a second vessel. A method of transfer involves lowering the pump into the first vessel; with the point extending into the liquid contained therein; withdrawing the piston through a first distance such that a volume of liquid substantially exceeding the volume to be transferred is drawn into the pump cylinder; raising the pump slowly, until the pointed part of the pump cylinder occupies a position above the surface of the liquid; advancing the piston through a distance which corresponds exactly to the first and second distances so that the desired amount of liquid is dispensed to the second vessel. Immediately after dispensing the required amount of liquid to the second vessel, the piston is again withdrawn through a short distance, to prevent a liquid droplet from forming on the point of the pump cylinder. The method of transfer also contemplates a procedure for washing the pump prior to transferring a second sample, which comprises completely emptying the pump into a waste outlet, drawing washing liquid into the pump, and expelling the washing liquid from the pump.

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First Claim