Page:The New International Encyclopædia 1st ed. v. 12.djvu/353

* LIQUEFACTION OF GASES. 313 LIQUEUR. many investigators, notably by Professor Dewar. A few facts may be noted here. The electrical resistance of metals decreases as the temperature is lowered, and in many cases the relative order of metals with reference to their electrical re- sistance is changed at low temperatures. Thus, at ordinary temperatures silver is a better con- APPARATU8 OF HAMPSON FOE THE LIQUEFACTION OP AIR. The gas to be liquefied is introduced through the small tube at the top under a pressure of about 120 atmospheres entering at ordinary room temperature. This tube is ex- tended downward in a spiral wound round the central col- umn ; and at its lower end there is an expansion-valve which is regulated from above by means of a screw. (The details are shown in the second cut.) The gas, cooled by expansion. i)a88es up through the apparatus and out again by the large pipe shown at the upper end. The coil a, carrying the compressed gas, ends in the jet d, which can be opened or closed by the screw c, regulated from above. The path of the gas after expansion is shown by the arrows. The regenerative principle is evident. ductor than copper, whereas at — 200° the re- verse is true. The thermo-electric properties of bodies change to a marked degree. The mag- netic moment of magnets is increased by .30 or 40 per cent, as the temperature is lowered to — 200°. The elastic constants of bodies increase by as much as four or five times when the temperature is lowered from + 15° to — 182°. Rubber becomes brittle. Changes of color often take place, the original hue, however, returning in all cases when the temperature is restored. There are many curious phosphorescent phe- nomena at low temperature. Milk becomes high- ly phosphorescent. . egg shines as a globe of blue light. Chemical affinity is almost complete- ly destroyed by cold : phosphorus, sodium, and potassium when placed in liquid oxygen remain absolutely unaffected. Photographic films re- tain only about one-fifth of their ordinary sen- sitiveness to light. Some interesting experiments have been tried dealing with vital phenomena at low tempera- tures. Warm-blooded animals, of course, perish at comparatively high temperatures, but it was found that bacteria can bear with impunity al- most any temperature however low. Sterilization does not result even after an exposure for one hour to a temperature of — 182° ; the germinat- ing power of seeds is also unimpaired; blood, meat, and milk when scaled in glass tubes under- go putrefaction in the ordinary course. In other words, life can exist at 21° from the absolute zero, and probably much nearer, under conditions which nevertheless almost completely stop chemi- cal and molecular action. It may be interesting to note in tabular form a few of the physical constants of the ga.ses and their liquids. SUBSTANCE Critical teoi per- ature Boiling- point at atmos- pheric pressure .lcohol -1-243.6° C. Ammonia 4-130 Argon —121 (j'arbon dioxide -J- 31 Carbon monoxide.. — 141 Fluorine [—120(7) Hydrogen Nitrogen — 146 Oxygen ^118 Water -|-358.1 -f78.3°C. — 33.7 —187 — 78 —190 —187 —253 -194.5 —183 -1-100 Freezing- point -130° C — 75 " —189.6 — 65 -207 — 258» —214 Color of liquid Colorless Tellovr Colorless Paleblue Colorless •At a pressure of fifti'-flve millimeters of mercury. In connection with these figures it should be stated that there are several lines of argument, based upon physical experiments, which lead .scientists to believe that it is impo.ssible for us to obtain by any physical means a tem])erature lower than about — 273° C. This temperature is called 'absolute zero,' and the nearest approach made to it by any experiments so far performed was in one bj' Professor Dewar when he solidi- fied hydrogen, obtaining a temperature only 1.5° above the absolute zero. BiBUOGR.vPHT. A complete history of the sub- ject of liquefaction of gases will be found in Hardin, The Rise and Development of the Lique- fnction of Gases (Xew York. 1899). There is also an interesting article by iliss Agnes M. Gierke in the Proceedintis of the Royal Inslitu- tion of Great Britain, vol. xvi., p. 699, 1901, on "Low Temperature Research at the Royal Insti- tution, 1893-1900." LIQUEUR (Fr.. liquor). The name given to any alcoholic preparation which is flavored or perfumed and sweetened to be more agreeable to the taste. JIany of the most famous liqueurs were first made by monks as cordials for the sick, and tlie secret of their composition has been transmitted from one generation to another in convents and monasteries. Aniseed cordial is prepared by flavoring weak spirit with aniseed, coriander, and sweet fennel-seed and sweetening with clarified syrup of refined sugar. Clore cordinl. much sold in the London gin-shops, is flavored with cloves, bruised and colored with burned sugar. I'eppcrmint. a common liqueur, especially among the lower classes of London, consists "of the ordinary sweetened gin. flavored with essential oil of peppermint, which is pre- viously rubbed up with refined sugar. .mong the other commercial liqueurs, the following are the chief varieties: Absinthe, ani- sette, bf-nC'dictine. cassis, chartreuse, crf-me de mentbe, creme de rose, crf-me de vanilla, etc.. curacoa. kirschwasser. kiinunel. maiascliino, noyau, pomeranzen, ratafia, trappistine, usque-