Almost all the devices in use at the present time for filling tubes or bottles with definite quantities of fluid depend for the vis a tergo on the gravity of the fluid column. When wishing to depart from this simple method, as is sometimes desirable or necessary, one is confronted with several difficulties. To overcome these, rather expensive and complicated appliances are necessary, the manipulation of which requires considerable time. The pump I have devised was suggested by the respirator sometimes used by chemists when working with dangerous gases.
The apparatus consists of two glass valves, a graduated burette, and a piston syringe. Each valve, A A′, consists of a capsule into which is fitted a very carefully ground stopper, B B′. These stoppers are weighted with mercury so that they will sink into place quickly and accurately. These valves are connected with the graduated burette as shown in the