408        Recent  Literature  Relating  to  Pharmacy.    { Amligusi,Srm 
occasion,  20  c.c.  of  liquid  hydrogen  were  collected  in  about  five 
minutes,  and  on  May  12th  50  c.c.  were  obtained  before  the  hydrogen 
jet  froze  up  from  the  solidification  of  air  in  the  pipes.  The  yield  of 
liquid  was  about  I  per  cent,  of  the  gas.  The  hydrogen  in  the 
liquid  condition  is  clear  and  colorless,  showing  no  absorption  spec- 
trum, and  the  meniscus  is  as  well  defined  as  in  the  case  of  liquid  air. 
The  liquid  must  have  relatively  high  refractive  index  and  dispersion, 
and  the  density  appears  to  be  in  excess  of  the  theoretical  value,  0-18 
to  012,  deduced  respectively  from  the  atomic  volume  of  organic 
compounds,  and  from  the  limiting  density  found  by  Amagat  for 
hydrogen  gas  under  infinite  compression.  The  author's  experi- 
ments on  the  density  of  hydrogen  in  palladium  gave  a  value  o  62 
for  the  substance  in  combination,  and  it  will  be  interesting  to  find 
the  density  of  the  actual  liquid  at  its  boiling  point.  Not  having 
arrangements  at  hand  to  determine  the  boiling  point,  two  experi- 
ments were  made  to  prove  the  excessively  low  temperature  of  the 
boiling  fluid.  In  the  first  place,  a  long  piece  of  glass  tubing,  sealed 
at  one  end,  but  open  to  the  air  at  the  other,  and  cooled  by  immers- 
ing the  closed  end  in  liquid  hydrogen,  immediately  filled,  where  it 
was  cooled  with  solid  air.  The  second  experiment  was  made  with  a 
tube  containing  helium. 
The  Bulletin  of  the  Cracow  Academy  for  1896  contains  a  paper 
by  Professor  Olszewski,  entitled  "  A  Research  on  the  Liquefaction 
of  Helium,"  in  which  he  states  that  "  as  far  as  my  experiments  go, 
helium  remains  a  permanent  gas  and  apparently  is  much  more  diffi- 
cult to  liquefy  than  hydrogen."  Helium,  which  has  been  extracted 
from  Bath  gas  by  the  liquefaction  method  described  last  year  (Proc. 
Chem.  Soc,  1897, 13,  190),  and  sealed  up  in  a  bulb  with  a  narrow  tube 
attached,  was  placed  in  liquid  hydrogen,  and  a  distinct  liquid  was 
seen  to  condense.  A  similar  experiment,  made  with  the  same  helium 
tube  in  liquid  air  under  exhaustion,  instead  of  in  liquid  hydrogen,  gave 
no  visible  condensation.  It  would  thus  appear,  as  already  suggested 
by  the  author  (Joe.  cit.),  that  there  cannot  be  any  great  difference  in 
the  boiling  points  of  helium  and  hydrogen.  A  fuller  account  of  the 
work  will  appear  in  the  Transactions. 
All  known  gases  have  now  been  condensed  into  liquids  which 
can  be  manipulated  at  their  boiling  points  under  atmospheric  pres- 
sure in  suitably  arranged  vacuum  vessels.  With  hydrogen  as  a 
cooling  agent,  it  will  be  possible  to  get  within  20°  or  300  of  the 
