SURVEY OF EXTREME COLD

King Country Chronicle, Volume XXVII, Issue 4460, 21 October 1933, Page 6

SURVEY OF EXTREME COLD

SURPRISING RESULTS OF LOW TEMPERATURE. The production of the greatest possible djegree of cold has been a goal of scientific achievement. Lake the conquest of earth's highest mountain peak, successive attacks have brought that goal ever nearer of attainment until we may now say that it lies practically within our grasp, for temperatures which lie within one degree Centigrade of the lowest conceivable temperature have (been reached. The chief stages in this long and arduous descent to the nadir of cold have been: The discovery of the method of Lique fying gases by pressure (Faraday, 1823); the liquefaction of air in bulk, by a process of cumulative cooling, due to the internal work done in the expansion of compressed air (Ljmde, 1896); the liquefaction of hydrogen gas, by the same method, after preliminary cooling of the hydrogen with liquid air (Dewar, 1898); and, finally, the liquefaction of helium, after pre cooling with liquid hydrogen (Earnmerlingh Onues, 1908). NEAR ABSOLUTE ZERO. The temperatures, measured downward from, zero, on the Centigrade scale, attained in these successive stages, are: Liquid air, 190 deg.; liquid hydrogen, 253 deg.; and liquid helium, 268.7 deg. Theoretical considerations place the absolute zero—thle temperature at which matter is deprived of all heat —at 273.2 deg. below zero Centigrade. Thus, the perature of liquid helium is within five degrees of absolute: zero. Still closer approach to this lowest limit can be made b(y causing the liquid to undergo rapid evaporation into a vacuum. The objective of these efforts towards complete and utter refrigeration of matter —efforts in which final success has been achieved usually only after repeated failures—has not, as a rule, been of a commercial character. It has had the purely scientific character of obtaining knowledge of the properties and behaviour of substances when cooled so far below the state in which we aije normally acquainted with them. STRIKING CHANGES. Even at liquid air temperature, and more markedly, naturally, at that of liquefied hydrogen, these changes are striking enough. All liquids, such as alcohol,, ether, and petrol, are frozen to a solid mass, and all gases, w|ith the one exception of helium, can be similarly liquefied, or solidified, under moderate pressure. But even solid bodies undergo strange alterations. Wlhen Dewar first publicly demonstrated the production of liquid hydrogen at the: Royal Institution in 1904, he dipped into the frigid liquid contained in “ Dewar ” flasks now familiar as the thermos —two small bel’s, one made of musically tinkling silver, the other of dull-sounding lead. When he withdrew them after an interval sufficient to allow them to attain the low temperature of the medium in which they were immersed, the Ijead bell rang with a clear note, and the silver bell sounded as lead. The elastic properties of these metals had undergone a complete inversion. EXTRAORDINARY EFFECTS. Another effect of a spectacular kind is the remarkable power of storing up light from an arc lamp while immersed such as paraffin, wax, eggs, or feathers acquire. An egg subjected to strong light from an arc lamp while immersed in the liquid hydrogen shone on its removal so brightly that print could easily be read by its light. Other effects are the extraordinary reduction in thei'mal activity, and in this resistance which metals offer to the flow of electric current. Wlhen the Dutch scientist Kamtmerlingh Onnes looked for this latter effect in metals cooled within a few degre/es of absolute zero by imjmersion in liquid helium —expecting no doubt merely to find their resistance still further reduced in proportion to the lowering of temperature—a surprise awaited him; the resistance had completely vanished, or at least had become immeasurably small. He had discovered the property of “ super-conductivity.” DREAM OF AMAZING POWER. The remarkable nature of this property may be illustrated by the statement that a single wire of super-con-ducting metal would transmit electric power from Niagara Falls to Melbourne with far less loss than a cable of 20 such wires would transmit the same power from Yallourn to Melbourne. But dreams of such a sysam of long-distance power transmission are vain, for the magnetic effect associated with the flow of current in the wire is found to counteract thte influence of low temperature and restore to the wire a measurable degree of electrical resistance as soon as the current reaches a certain moderate strength. Nevertheless, the scientific interest of the extraordinary effect of extreme cold is very great, more especially since all attempts at theoretical explanation have so far failed. It certainly defends in some way upon the degree of perfection of crystalline structure of the metal, and in a gene-

r.al way must be ascribed to a cessation of all movement of the atoms from their prescribed places in that structure. The liquefaction of helium gas was first effected at the University of Leiden, in Holland, in 1908. Not until 1923 was a second plant constructed, this time at Toronto, Canada, for which supplies of helium gas were procured by Professor McLennan from the natural gas at Calgary, in Alberta. MANY LABORATORIES. Other cryogenic laboratories have since been created: at the Bureau, of Standards, in Washington, and at the John Hopkins and California Universities, in the United States; also at Berlin, in Germany; and quite recently at Oxford University. Russia is said to be planning a.large plant at Charkoiw; France, one at Paris; and Germany, a second at the University of Gottingen.

On 3rd February Mr Stanley Baldwin, in his capacity ,as Chancellor of the University of Cambridge, officially opened there the new Royal Society Mond Cryogenic Laboratory. This laboratory is/ equipped only for liquid hydrogen production, but in the near future it will also possess a heliutmliquefjying plant. Researches on the magnetic properties of metals at low temperature will form one of the chief items of the programme of investigations.

The initial cost of equipment of cryogenic laboratories has of recent years been much reduced by the improvements made in apparatus for liquefying hydrogen and helium —that installed at the Clarendon Laboratory in Oxford cost less than £SO0 —and the cost of supplies of helium gas, hitherto exorbitant, may well become criminal, if the United States Government, following upon the recent tragic disaster to its helium-filled airship, should decide, in the interests of scientific research, to release its immense reserves of this gas. It is certain that a thorough survey of the region around this extreme peak of cold will yield results of far greater interest and importance to mankind than thle successful mountaineer can hope for when first he looks upon the desolate waste of snow from the summit of Mpunt Everest. That, ultimately, results of industrial and economic importance—as have, indeed, followed upon the success of the researches directed to the liquefaction of air—’will emerge from this new knowledge as a by-product is a belief that majy also be cheerfully and confidently indulged. (K.G., in the Melbourne Age.)