Show BOILING POINTS thee these are innumerable and borm a cu rlou rious study it ia Is interesting to note that tho the temperature pera ture at which a liquid boila boils ia is t tho h 0 same oa as that at which its itil vapor is condensed precisely as tho temperature temper aturo at which water freezes is the samo same as that at which ico ice melts it may seem superfluous to observe that thero there aro are more boiling points than tho the boiling point of water if it were not so all bodies would bo be in in tho the soll solid d liquid or gaseous state together and hiie life would bo be impossible it is partly by giving every substance its ow own a boiling point or rather its own set of boiling points for the fixed temperature oven even zt f for 1 the same substance is a fallacy bat nature has rendered ed our physical environment suitable to our needs what is generally understood by tho the boiling point of water is a temperature of degrees on tho the fahrenheit ther Pao metrio scale but alpine climbers clim bera know latow well that on a high mountain water boila boils at a very much lower temper aturo on ou the summit of me mont nt biano blano nt at degrees the reason is that at these altitudes the pressure of t the he at mo sphere is very much reduced since the density of the air decreases with tho the distance above the earths surface and the water expands at a correspondingly lower temperature passing more read ily into the vaporous condition in which the volume of a given mass of any ally sub stance is always far greater than that r of the same mass when liquid the boiling point of liquid is is therefore seen to depend not only on temperature but also on pressure and tho the bailin boiling 9 point bof of water at degrees corresponds to what ia is called a pressure of one atmosphere approximately 15 pounds to the square inch or the pres sure capable of supporting tho column of mercur mercury yin in a mercurial barometer tat at a height of 20 9 inches this is 13 the average pressure of the atmosphere at the sea level and it if it is reduced the boiling point is is lowered while it if it is is increased the boiling point is raised A very curious result is arrived at tit if wo we place a vessel of water in the re beiver of an and aud reduce the pressure to of an atmosphere for then the water boi boils Is at 82 degrees that is at its freezing point under ordinary pressure since it is now possible to produce an almost perfect vacuum water may bo be boiled at still lower temperatures pera tures all liquids do not boil at the same samo temperature thus while water wate andor a pressure of one atmosphere boils at degrees alcohol which passes more readily into the state of vapor boils at 1728 8 degrees and ether at 03 8 degrees which ia is below the normal temperature pera per ture aturo of the body since increase of pressure retards the vaporization of a I 1 liquid it of course facilitates tho liquefaction of agase a gag by y assisting the process proem of contraction consequently many gases are capable of being liquefied by pressure alone though only when they aro are below what is called their critical temperature different for every different gas above which cold as well as pressure becomes ec essary oxygen hydrogen b drogen and nitrogen aro are the most remarkable axa oxa examples amples of gases having low critical temperatures and it is only recently that their liquefaction has been accomplished at all they were long thought to bo be permanent gases but it is now known that all gases are liquefiable the boiling points of oxygen and nitrogen are respectively 8 degrees and degrees F below the fr freezing eez point of water and therefore those these are the highest temperatures at which thoy they can cau exist as liquids to produce these extremely low temperatures it is necessary to employ great pressure along with freezing mixtures mix turea the most remarkable liquefaction which has yet been accomplished is that of air it was supposed that the oxygen and nitrogen having different boiling points they would liquefy separately tely this is not the case hie the mixture laiq liquefies u f les as air and presents presen ts the appearance appear ace of water but on being again evaporated the nitrogen evaporates first and the oxygen afterward thia this is a puzzle in physics which will doubtless be ox ere long good words |