422 
Varieties. 
fAm.  Jour.  Pharm, 
t      Sept.  1875. 
gaseous  mixture,  richer  in  oxygen,  is  withdrawn  from  the  water  and  again 
absorbed,  it  follows,  from  the  multiplication  of  the  two  coefficients  of 
absorption  with  the  volume  proportions  0*67  N  and  0*33  O,  that  the 
gaseous  mixture  now  taken  up  has  the  composition  0*525  N  :  0*475  O  v 
a  third  absorption  raises  the  result  to  0*375  N  :  0*625  O  ;  a  fourth  to 
0*25  N:o*75  O;  and  a  fifth  to  0*15  N  :  0*85  O,  the  proportion  in 
which  the  two  gases  occur  in  Tessie  du  Motay's  oxygenous  mixture. 
After  the  eighth  absorption,  the  gas  is  almost  pure  oxygen  (0*973  ^ 
0*027  N)- 
Mallet's  apparatus  consisted  of  a  larger  or  smaller  number  of  strong 
iron  water-holders  connected  with  each  other  by  means  of  suction-  and 
forcing-pumps.  Into  the  first  air  is  driven  through  fine  apertures  at  a 
pressure  of  about  five  atmospheres.  The  unabsorbed  nitrogen  escapes 
by  a  valve.  The  absorbed  gas  is  now  extracted  by  the  second  pump 
from  the  first  receiver  and  forced  into  the  second.  With  a  series  of  four 
receivers  the  operation  lasts  five  minutes.  If  the  receivers  serially 
decrease  in  size,  the  first  holding  10  cubic  metres  and  the  last  5,  the 
result  of  a  continuous  working  of  the  process  is  7760  litres  per  hour  of 
a  gaseous  mixture  containing  75  per  cent,  of  oxygen,  or  168  cubic 
metres  in  twenty-four  hours.  The  cost  of  working,  wear  and  tear,  and 
supervision  are  said  to  be  insignificant.  Where  motive-power  is  cheap, 
/.  water-power  or  the  waste  heat  of  metallurgical  processes,  this 
method  may  consequently  be  applicable,  especially  for  use  in  such  met- 
allurgical operations  where  a  mixture  comparatively  poor  in  oxygen  is 
serviceable. 
If  we  sum  up  the  results  of  our  survey  of  the  methods  for  the  indus- 
trial preparation  of  oxygen,  we  must  place  Tessie  du  Motay's  process 
in  the  first  line,  as  well  tried  and  proved,  and  in  the  second  Mallet's 
mechanical  process  as  just  described. 
Finally,  we  pass  to  the  question.  To  what  applications  has  oxygen 
hitherto  been  put  ?  As  the  supporter  of  combustion,  we  owe  to  it  heat 
and  light ;  and  as  the  medium  of  respiration,  it  is  the  condition  of  life.. 
(To  be  continued.) 
VARIETIES. 
Some  of  the  Properties  of  Grindelia  Robusta.  By  Henry  M.  Fiske,  M.D. 
— The  Grindelia  robusta  is  an  herbaceous  plant,  perennial,  and  a  native  of  the  West 
Coast  of  America,  flourishing  luxuriantly  between  the  28th  and  52d  degrees  of 
