STEAM  APPARATUS  FOR  PHARMACEUTICAL  PURPOSES.  225 
ner :  When  the  steam  begins  to  form  in  the  boiler,  it  presses 
upon  tbe  water  and  forces  it  out  and  up  the  open  tube  connect- 
ing with  vessel  E.  As  it  rises,  it  also  passes  through  the  flexi- 
ble pipe  attached,  and  flows  into  vessel  E,  when  by  its  weight 
it  passes  down  the  spiral  spring  and  closes  the  draft  valve  at  F. 
This  checks  combustion,  and  consequently  the  formation  of  steam 
and  as  steam  pressure  diminishes,  the  water  in  the  tube  falls  and 
passes  out  of  vessel  Ey  and  the  spiral  spring  raises  it  and  opens 
again  the  shaft.  Thus,  steam  pressure  perfectly  controls  com- 
bustion. If  but  little  steam  is  used,  but  little  fuel  is  consumed. 
The  vessel  E  is  placed  thirty-four  inches  above  the  water  level 
in  the  boiler,  thus  allowing  just  one  and  a  half  pounds  pressure 
to  accumulate,  before  the  draft  is  checked.  This  pressure  is 
sufficient  to  force  the  steam  through  six  hundred  feet  of  pipe  with 
facility.  The  tube  upon  which  it  slides  is  open  constantly,  so 
that  if  the  safety  valve  and  air  draft  both  become  obstructed 
all  the  water  will  flow  out  of  the  boiler,  at  three  pounds,  thus 
making  explosion  impossible. 
Fuel  is  fed  into  the  cylinder  at  the  top  of  the  apparatus  by 
removing  the  cover.  It  holds  a  supply  for  twenty-four  hours, 
and  as  it  is  consumed  below,  it  falls  down  to  the  fire  by  its  gravity. 
The  arrangement  for  feeding  water  is  exceedingly  simple  and 
effective;  it  is  not  clearly  shown  in  the  cut.  But  little  water  is 
required  except  when  the  process  of  distillation  is  going  forward, 
as  the  steam  is  condensed  in  the  retorts,  evaporators,  radiators, 
&c,  and  returns  to  the  boiler  again  through  the  same  pipes  that 
convey  it  away.  D  is  a  safety  valve  lifting  at  one  and  a  half 
pounds.  0  0 are  pipes  for  conveying  steam.  A,  steam  and  water 
cocks.  i,  handle  for  grate.  The  apparatus  is  portable,  and  may  be 
placed  in  a  basement,  or  in  the  laboratory  of  the  pharmaceutist. 
One  has  been  in  use  in  my  laboratory  for  many  consecutive  months, 
without  any  disarrangement  or  instance  of  failure.  By  con- 
necting radiating  coils,  it  is  made  to  do  the  work  of  warming  the 
building  in  addition  to  its  other  duties.  Broad  jacketed  pans  ot 
tinned  copper  are  used  for  evaporations.  The  steam  is  let  in  at 
the  bottom  through  an  inch  coupling,  and  as  it  condenses  it 
flows  back  again  to  the  boiler.  The  heat  is  controlled  per- 
fectly by  an  air  cock  attached  to  the  pan,  so  that  any 
temperature  between  100°  and  212°  F.  may  be  maintained. 
15 
