H. Monmouth Smith. The Nernst Lamp. Science. November 18, 1898, pp. 689 - 690

The Nernst Lamp.

The Frankfurter Zeitung contained recently a very interesting account of Professor Nernst's new electric lamp. As information on this subject has heretofore been so difficult to obtain, a brief abstract from this article may be of interest to the readers of Science.

Fig. 1.

Fig. 2.

As has been previously announced, Professor Nernst employs magnesium oxide for the illuminating material which at ordinary temperatures is a non-conductor, but when heated to a sufficiently high degree (and herein lies Professor Nernst's discovery) becomes a perfect conductor and emits a brilliant white light. The preliminary heating of the magnesia (A) Professor Nernst accomplishes by placing it in the focus of a reflector (C) as seen in Fig. 1. On the inner side of the reflector is a spiral wire of platinum (D) which, when brought to incandescence by a current, produces heat sufficient to render the magnesia a conductor; a current is then passed directly through the oxide by the wire (B) and that in the spiral is shut off. A complicated form of lamp is seen in Fig. 2. Here the magnesia (A) is placed within a cylinder (C), which also encloses a platinum spiral (D). As soon as the incandescent spiral has heated the magnesia sufficiently a current is passed through the oxide by the wire (B). Within this circuit is a coil (G) which upon becoming magnetic draws down the iron bar (E), thus lowering the now incandescent magnesia from within the cylinder. Upon breaking the circuit the coil loses its magnetism, and a spring (F) raises the iron bar and magnesia to their former positions.

As advantages over the ordinary incandescent lamps Professor Nernst claims that the same amount of light can be furnished at one-third the cost, and as the magnesia allows of being heated to a much higher degree than a carbon filament a purer light is obtained. The successful employment of a cheaper substitute for the platinum is also announced, though the name is not made public. In operating, either an alternating or direct current is used.

H. Monmouth Smith.
Hampden-Sidney, Va.

Walther Nernst homepage

Revised 2004-01-16