ON A THEORY CONCERNING THE SUDDEN LOSS OF MAGNETIC PROPERTIES OF IRON AND NICKEL.
By Mr. H. Tomlinson, B.A.
Experiments by himself and other observers have shown that the temperatures at which iron and nickel lose their magnetic properties depend on the specimens used and the magnetizing forces employed; but the temperatures at which they begin to lose these properties are definite—for nickel about 300° C., and iron about 680° C. The author's own experiments on "Recalescence of Iron" show two critical temperatures; and Pinchon has shown by calorimetric measurement that between 660° and 720° C., and between 1,000° and 1,050° C., heat becomes latent. All these facts seem to indicate a molecular rearrangement about these temperatures.
In his proposed theory he assumes that the molecules
of iron (say) contain magnetic atoms capable of motions of translation and of rotation. These tend to form closed magnetic circuits, but at ordinary temperatures are unable to do so on account of the close proximity of their centers. On raising the temperature their centers are further separated, till at about 680° C. their polar extremities rush together, forming complete circuits and exhibiting no external magnetic properties. On cooling down, the centers approach until the gravitation attraction overcomes the magnetic attraction of their poles, when the magnetic properties reappear.
Prof. Ayrton asked whether the author had made experiments on the reappearance of magnetic properties when raised to a white heat, and Prof. Thompson inquired whether cobalt had been tested. Both questions were answered negatively.
POISON OF THE SOMALIS, EXTRACTED FROM THE WOOD OF THE OUABAIO.
The principle in question, ouabaine, forms rectangular plates, very slender, of a nacreous appearance. It is absolutely white, inodorous, and not appreciably bitter. It contains no nitrogen, and does not react with coloring matters. At a boiling heat, in presence of dilute acids, it is split up, yielding a reductive sugar. Its composition is C90H45O12. It is poisonous if introduced into the circulation, but not if swallowed.—M. Arnaud, in Comptes Rendus.