Full Text
Simple Methods of Obtaining a Vacuum1
The brilliant solution of the problem of pumping out air and gases, given by Langmuir2, requires only one simplification, namely: the introduction of a simple
pump, which makes it possible easily and reliably to obtain a sufficient preliminary rarefaction, after which a Langmuir pump can carry out the final evacuation. Experiments carried out at the Physical Institute of the Moscow Scientific Institute by N. Ya. Selyakov, with the advice of P. L. Kapitsa, make it possible to resolve this last question as well. From the experiments it turns out that, in order to obtain a fore-vacuum, one may use an ordinary glass water-jet pump, provided only that a sufficient drying of the water vapor is produced, which can be done with phosphorus anhydride. Under these conditions, a small Langmuir pump connected in series makes it possible to obtain a rarefaction down to 0.01 mm of mercury, so that two Langmuir pumps connected in series together with the fore-vacuum achieved by a water pump can easily give the limiting rarefaction.
These investigations are of very substantial importance not only for laboratory practice, but also for technology in the broad sense of the word. In everyday life itself, at the present time, in view of the shortage of fuel, vessels of the “Thermos” type must come more and more into use, making it possible to keep water and food hot for a long time. These vessels require, as far as possible, complete evacuation, and here pumps of the type described will find wide application. Further, the evacuation of electric lamps and X-ray tubes will require a large number of pumps, and in this field the experiments described above may be very significant.
P. Lazarev.