Am.  Jour.  Ptn  rm.  I 
March,  1898.  / 
Editorial. 
EDITORIAL. 
LIQUEFIED  AIR. 
The  liquefaction  of  air  can  scarcely  be  considered  new,  but  the  production 
of  liquid  air  has  only  recently  been  accomplished  in  this  country  on  a  com- 
mercial scale.  This  fact  was  made  public  through  the  daily  papers  only  a  few 
weeks  ago,  and,  consequently,  has  not  yet  appeared  to  any  extent  in  the  scien- 
tific journals.  A  quantity  of  the  liquid,  2l/2  gallons,  was  brought  from  New- 
York  to  Philadelphia  in  a  milk-can  without  any  special  precautions.  In  its 
normal  condition,  air,  as  we  know  it,  is  a  gas,  just  as,  in  its  normal  condition, 
water  is  a  liquid  ;  but  if  we  lower  the  temperature  of  the  air  or  increase  the 
pressure  on  it,  or  both,  to  a  sufficient  degree,  we  reach  a  point  at  which  con- 
densation takes  place.  The  liquefaction-point  of  air  under  normal  atmospheric 
pressure  is  —  191°  C. 
A  process  for  the  commercial  manufacture  of  liquid  air  was  described  in  1S95 
{Journal  of  the  Society  of  Chemical  Industry,  Vol.  14,  page  984),  but  the  results 
do  not  appear  to  have  been  on  a  very  large  scale.  In  the  present  instance  the 
successful  production  of  liquid  air  is  claimed  by  Mr.  Charles  E.  Tripler,  of  New 
York.  His  process  is  based  upon  the  well-known  fact  that  if  a  gas  be  com- 
pressed and  then  allowed  suddenly  to  expand,  it  absorbs  the  heat  of  the  sur- 
rounding medium,  thereby  producing  intense  cold. 
According  to  this  method,  air  is  subjected  to  a  pressure  of  2,000  pounds  to 
the  square  inch,  passed  through  a  coil  and  permitted  to  issue  from  a  needle- 
point orifice.  There  it  expands  and  cools.  This  cold  stream  of  air  circulates 
around  a  second  coil  through  which  compressed  air  is  flowing,  reducing  the 
temperature  of  the  latter.  The  air  issuing  from  this  second  coil  has  its  tem- 
perature lowered  to  a  point  due  to  its  own  expansion,  plus  the  cold  imparted 
from  the  first  expansion.  The  expanded  and  extremely  cold  air  from  the 
second  coil  is  used  similarly  to  cool  a  third  coil,  the  air  in  which  is  brought 
down  to  a  temperature  of  —  191°  C.  and  below,  at  which  it  condenses  and  flows 
from  the  end  of  the  coil  in  a  liquid  stream. 
It  is  of  interest  to  note  some  of  the  properties  of  this  new  product.  Tin 
placed  in  the  liquid  causes  it  to  boil,  the  tin  becoming  brittle  as  glass.  Copper 
and  platinum  are  not  so  affected,  hence  it  is  believed  that  these  metals  will 
make  suitable  containers  for  the  liquid.  When  heat  is  applied  to  it,  it  boils,  as 
would  naturally  be  supposed,  with  excessive  ebullition  ;  but  when  water  is 
poured  into  the  boiling  liquid  the  water  is  instantly  frozen.  Alcohol  and  mer- 
cury are  likewise  frozen  when  brought  in  contact  with  the  liquid. 
Whatever  may  be  the  economic  applications  of  this  interesting  product,  it  is 
pretty  certain  to  play  an  important  part  in  laboratory  experimental  work. 
Attention  was  called  to  the  fact,  in  1895,  that  when  the  liquid  was  boiled  the 
nitrogen  was  vaporized  first,  so  that  the  latter  portions  consisted  of  nearly  pure 
oxygen.  It  was  then  shown  that  oxygen  could  be  prepared  by  mechanical 
means.    Other  uses  for  this  liquid  will,  no  doubt,  rapidly  suggest  themselves. 
Especially  does  it  seem  probable  that  it  will  become  one  of  the  most  eco- 
nomical means  of  producing  artificial  cold.  Since  mechanical  means  only  is 
necessary  for  its  production,  it  ought  to  become  very  cheap,  and  at  the  same 
time  it  will  be  free  from  the  dangerous  character  of  liquid  ammonia. 
