62 
Lecture  Experiments, 
(  Am.  Jour.  Pharm. 
I    Feb.  1,  1871. 
city.  The  balloon  is  provided  at  both  sides  with  tubulures  through 
which  glass  tubes,  ending  in  platinum  tips,  are  carried.  The  water 
which  is  formed  flows  out  of  the  neck  of  the  balloon.  In  an  experi- 
ment in  which  the  air  in  the  balloon  had  not  been  replaced  by  hydro- 
gen, and  the  hydrogen  had  burnt  for  some  moments  in  the  oxygen 
circulating  about  it,  and  the  first  drops  of  water  had  run  down  into 
the  flask  placed  to  receive  it,  I  was  astonished  to  see  the  vessel  filled 
with  red  vapors,  the  quantity  of  which  increased  when  the  corks 
which  fastened  the  glass  tubes  in  the  lateral  tubulures  were  momenta- 
rily closed.  The  smallest  drops  of  the  water  running  out  reddened 
litmus  paper  ;  the  solution  plainly  tasted  sour,  and  gave  with  sul- 
phuric acid  and  sulphate  of  iron  the  reaction  of  nitric  acid. 
In  a  trial,  in  which  30  grms.  of  water  had  formed  within  thirty 
minutes,  the  fluid  was  saturated  with  ammonia,  and  the  solution  was 
evaporated  in  a  large  watch-glass  upon  the  water-bath.  After 
cooling,  an  abundant  crystallization  of  the  characteristic  needles  of 
nitrate  of  ammonia  made  its  appearance. 
Finally  it  may  be  remarked  that  the  apparatus  which  is  here 
described  illustrates  exquisitely  the  process  of  formation  of  the  water. 
5.    Fluid  Qyanogen. 
Cyanogen  belongs  to  the  easily  liquefiable  gases.  At  20°  four,  and 
at  0°  only  IJ  atmospheres  are  necessary,  in  order  to  condense  the 
cyanogen  gas.  At  — 21°  the  cyanogen  at  the  usual  atmospheric  pres- 
sure is  fluid,  and  in  the  neighborhood  of  the  point  of  soiidifaction  of 
mercury  it  is  solid.  The  phenomena  of  liquefaction  is  as  easily  ob- 
served in  the  case  of  cyanogen  as  it  is  in  that  of  sulphurous  acid. 
Hitherto  in  lectures,  when  it  was  desired  to  show  that  cyanogen  is 
liquefiable,  the  experiment  has  been  performed  either  in  a  Faraday's 
tube,  or  in  the  well  known  compression  apparatus  of  Magnus.  The 
cyanogen  is  easily  obtained  in  the  fluid  condition  by  both  methods. 
But  the  quantity  that  is  condensed  is  always  very  limited,  and  scarcely 
visible  at  considerable  distances.  Moreover  the  experiment  loses  much 
from  the  circumstance  that  the  cyanogen  cannot  be  allowed  to  kream 
out  in  the  atmosphere,  so  that  it  can  be  recognized  by  its  properties, 
its  flame  for  example. 
The  ease  with  which  condensed  sulphurous  acid  can  be  preserved 
in  vessels  provided  with  glass  cocks,  gave  the  inducement  to  con- 
dense large  quantities  of  cyanogen  in  strong  glass  tubes,  to  the  mouth 
of  which  a  Geissler's  glass  stop-cock  was  fused.    It  shortly  became 
