A  M.  JOTJR.  PhARM.  ") 
Feb.  1,1871.  J 
Lecture  Experiments. 
63 
evident  that  a  glass  cock  was  not  necessary  for  this  purpose,  since  it 
sufficed  to  connect  a  brass  cock  in  the  ordinary  manner  to  a  glass 
tube. 
The  mode  of  experiment  which  was  finally  adopted  as  the  most 
'Convenient,  is  the  following  : 
Upon  an  ordinary  combustion  tube  of  about  30  centimetres  length, 
fused  together  at  one  end,  a  brass  socket,  into  which  a  brass  cock  can 
be  screwed,  is  fastened  with  sealing  wax.  In  order  to  remove  the  air 
from  the  apparatus  a  thin  delivery  tube  is  passed  through  the  open 
cock  to  the  bottom,  and  a  stream  of  cyanogen  conducted  in,  until  the 
gas  which  issues  out  of  the  opening  exhibits  a  pure  cyanogen  flame. 
The  delivery  tube  is  then  removed  and  the  cock  closed. 
Two  strong  litre  flasks,  which  are  provided  at  the  bottom  with 
tubulures,  serve  as  the  apparatus  for  condensation.  The  two  flasks 
are  connected  by  an  India  rubber  tube  of  1 J  meters  length,  which  is 
sewed  into  a  covering  of  linen.  One  flask  is  placed  somewhat  higher 
than  the  other,  in  such  a  way  that  when  the  one  which  is  the  lowest 
is  filled  to  the  neck  with  quicksilver,  the  mercury  streams  through 
the  lateral  tubulure  into  the  flask  which  stands  above.  Into  the  neck 
of  the  flask  which  is  filled  with  mercury  a  glass  tube  bent  twice  at 
right  angles  is  fastened  ^by  means  of  a  good  cork,  that  is  secured 
moreover  by  wire.  This  tube  is  then  connected  to  a  cyanogen  appa- 
ratus. The  latter  is  best  made  of  a  difficultly  fusible  tube,  which  is 
provided  with  a  bulb  for  the  reception  of  mercury.  It  is  slowly 
heated  in  a  combustion  furnace.  In  proportion  as  the  higher  flask  is 
lowered  and  the  mercury  flows  out,  the  flask  which  held  the  mercury 
i  filled  with  cyanogen. 
After  these  preliminaries  the  condensation  tube  is  placed  for  a 
quarter  of  an  hour  in  a  good  freezing  mixture  (ice  and  common  salt, 
to  which  some  chloride  of  calcium  has  been  added,)  that  has  a  tem- 
perature of  — 25°.  The  cyanogen  apparatus  is  then  removed,  and  the 
end  of  the  exit  tube  is  counected  with  the  orifice  of  the  condensation 
tube,  the  latter  always  remaining  in  the  freezing  mixture.  This  is 
easily  done  by  means  of  a  stout  india-rubber  tube,  which  is  fastened 
moreover  by  means  of  cord.  It  is  now  necessary  only  to  raise  the 
lower  flask  and  allow  the  mercury  to  flow  into  the  one  that  is  filled 
with  cyanogen.  As  soon  as  the  level  of  the  mercury  has  reached  the 
neck  of  the  flask,  the  cock  is  closed  and  the  tube  is  taken  out  of  the 
ice. 
