Fig. 35.
A narrow tube G is joined to D of [Fig. 34], and terminates in the wide tube I, which is connected above to H, and below to the air-trap J. J is connected at K, by a piece of flexible tube, to a reservoir of mercury, from which mercury enters the air-trap, and passing thence to I, can be employed for filling the V-trap HLG. The air-trap J is in the first instance filled with mercury, and then serves to intercept any stray bubbles of air that the mercury may carry with it. The particular form of the trap shown at HLG was adopted because with it the arm LG is more readily emptied of mercury than with any other form of trap made of small tube that I have tried. It has been used in my apparatus in the following manner:—H was connected with a vessel to be filled with pure oxygen, the tap E closed, and the rise of mercury above L prevented by a clamp on the flexible tube; the vessel to be filled and the trap were then exhausted by a Sprengel pump, and oxygen allowed to flow into the exhausted space by opening E, the operation of exhausting the tubes and admitting oxygen being repeated as often as necessary.
To prevent access of air to E on disconnecting the vessel at H, the mercury was allowed to flow into the trap till it reached to MM. E was then closed, and H exposed without danger of air reaching E, the length of the arms of the trap being sufficient to provide against the effects of any changes of temperature and pressure that could occur.
A delivery tube may be connected to H and filled with mercury, by closing E and raising the mercury reservoir. All air being in that way expelled from the delivery tube, and the supply of mercury cut off by clamping the tube from the reservoir, oxygen can be delivered from the tube by opening E, when it will send forward the mercury, and pass into a tube placed to receive it without any risk of air being derived from the delivery tube.
(2.) Gimmingham’s Vacuum Tap,[15] shown in [Fig. 35], consists of three parts. A tube A is ground to fit the neck of B. B is closed at its lower end, and has a hole d drilled through it; when B is fitted to C, d can be made to coincide with the slit e. When A, B, C are fitted together, if d meet e, there is communication between any vessels attached to A and any other vessel attached to C, entrance of external air being prevented by mercury being placed in the cups of C and B. The tap may be opened and closed at pleasure by rotating B.
Fig. 36.
