The daily morning journal and courier., 1899-06-19
Air as d Liquid.

Air as Liquid.
 | (From the Independent by George F. Barker, IL. D., Professor of
 Physics in the University
 of Pennsylvania.
 | The world of our experience is very | narrow one. Whatever our eyes have | not seen, our ears and our hands have ] not handled, is to us practically non-eX- :, istent. In whatsoever direction we con- slider our surroundings, whether with reference to size or to weight to pres | sure or to temperature, we observe that | it requires but a very minute variation | in these quantities to completely change | our knowledge of things and to give us an entirely new consciousness. Sir Wil- | liam Crookes in a recent address pie l lures a homunculus on a cabbage leaf vainly struggling with the mysteries of a dew drop. To being so minute, the molecular properties of water are of vastly more importance than it's proper 1 ties en masse, and he utterly fails to recognize it as water, as we do, because to him its molecules are so big. It is | quite the same in the matter of temper ature. To prove it we have only to
 think how entirely different this world
 would be if the mean temperature upon | it's surface were a few hundred degrees higher or lower than it is at present. | How many substances which we know now as liquids would be either gases on
 the one hand or solids on the other.
 Upon the sun, the forms of matter we | know as metals exist as vapors and as
 these condense fall as a fiery rain, while in the outer regions of space the intense cold permits batter of all sorts to exist | only in the solid state.
 Perhaps no illustration of this rela- tivity in our consciousness can be more apt than that relating to the existence
 of air as a liquid, It is true, indeed,
 that gases in small quantities have been
 transformed into liquids in the chemists laboratory, and have been shown to stu
 dents in the lecture room. But it Is only
 when the process assumes commercial
 proportions and air is liquefied by the | gallon and made available to everybody that the masses awaken to a realization | of it's remarkable properties. True, it Is
 a liquid; but 1t is a liquid which does
 not wet anything A handkerchief
 soaked in it and then shaken out, is as
 dry as before, It may be poured into a
 tumbler as may any liquid, but, unlike
 any known liquid, it boils furiously even
 in the ordinary air, and in boiling pro-
 duces a cold several hundred degrees be-
 low the zero of the thermometric scale.
 Of itself it does not give off a vapor;
 but the gas resulting from it's evapara-
 tion condenses to solid the moisture in
 the air and so surrounds itself with an
 almost impenetrable mist or fog At
 such a low temperature most substances
 lose their characteristic properties, Iron
 becomes as brittle as glass, copper loses
 it's electric resistance, soft rubber IS
 made hard and fragile, mercury is solid
 flied and absolute alcohol which is able
 to stand the winters cold of the Arctic
 regions. is converted into a hard and
 dense solid like ice. Certainly it would
 seem that our ordinary experiences are
 wofully disturbed by such substance
 and our consciousness of things about
 us caused to suffer very rude shock
 It is not due to our sense of the improp-
 able and the unexpected that we take
 so general an interest in this liquid ar
 Tn order to change a gas into liquid,
 either cold or pressure or both must De
 applied to it. And when so applied m sufficient measure all the known gases
 may be reduced to liquids. Some or
 these gases. such, for example, as car bonic acid may be liquefied at the ordi-
 nary temperature by pressure alone,
 Others like oxygen, cannot be liquef1ed
 nv any amount of pressure unless pre-
 viously cooled to a certain low tempera-
 ture which is called the "critical tenn
 perature." But if sufficiently cooled all
 gases can be converted into liquids
 without any increase of pressure. Thus,
 if oxygen be cooled to 1So degrees below
 the Centigrade zero it becomes liquid even at the pressure of the atmosphere
 Of nitrogen, at minus 194 degrees. the
 same is true. Air, therefore, whlch IS mixture of these two gases, may be sim ilarly converted into liquid simply py
 cooling it to minus 191 degrees. Ordl-
 uarily. however 1t is more convenient to effect the liquefaction by the use of both cold and pressure. In the earlier pro- . cesses for liquefying the more perma- nent gases the necessary degree or coll was secured by the evaporation of a more readily condensible gas. Thus Pictet. who in 1877 first liquefied oxygen produced his cold in two successive
 stages by evaporatng under diminished l pressure, first, liquefied sulfurous oxide and then liquefied carbonic acid In , this way he produced cold of minus 12O degrees C., at which temperature since it is below the critical temperature | of oxygen. a pressure of fifty pounds , sufficed to effect the liquefaction. The remarkable investigations made by De- ) war at the Royal Institution of Great Britain within the last few years with these liquefied gases, in which he has proved and in many cases accurately measured the marvellous changes which . matter undergoes at these low temper
 atures, which Investigations eliminated a year ago in the reduction to liquids ol , hydrogen and helium, the last remain } ing gases, were made for the most part
 by means of gases liquefled by the meth ad of Pictet as modified by himself.
 In the same year with Pictet, the = French physicist Cailletet succeeded ir - producing the necessary cold for lique- 3 faction by the expansion of the com
 pressed gas itself Evidently since t gas, when compressed, Is heated, it must
 be cooled when it is expanded Hence l if we suppose air to be compressed to g
 hundred and fifty atmospheres or there f abnuts, and subsequently, cooled by a =