LIQUEFACTION  OF  PROTOXIDE  OF  NITROGEN.  275 
sulphuric  acid  upon  a  watch-glass,  and  allow  it  to  stand  for  a 
quarter  of  an  hour.  If  it  be  pure  jalap-resin  it  will  be  gradually 
dissolved,  assuming  a  beautiful  crimson  color,  and  in  a  few  hours 
a  brown  viscid  resin  will  separate."  He  continues:  "  I  have 
made  the  same  experiment  with  common  resin9  with  scammony, 
etc.,  but  none  of  these  evinced  the  characteristic  relation  towards 
concentrated  sulphuric  acid,  which  is,  therefore,  an  infallible 
test  for  jalap  resin."  Here  I  am  desirous  of  showing  that, 
though  the  sulphuric  acid  test  distinguishes  jalap  resin  from 
some  other  resins,  it  does  not  distinguish  it  from  that  of  scam- 
mony.  It  will  be  clearly  observed  from  the  watch-glasses  upon 
the  table — the  one  containing  jalap  resin,  and  the  other  scam- 
mony  resin — that  the  rose  color  is  so  similar  that  it  would  be 
impossible  to  tell  the  one  from  the  other.  The  inferences  to  be 
drawn  from  the  foregoing  appear  to  be : — 
That  the  P.  B.  process  for  the  preparation  of  jalap  resin  is 
good  ;  that  worm-eaten  jalap  certainly  possesses  no  advantage 
over  sound  jalap,  but  rather  the  contrary,  for  the  preparation 
of  resin  of  jalap  ;  that  good  Tampico  jalap  is  a  valuable  substi- 
tute for  the  Vera  Cruz ;  that  methylated  spirit  is  objectionable 
in  the  preparation  of  this  and  similar  resins  or  extracts ;  and 
that  concentrated  sulphuric  acid  is  not  a  distinguishing  test  be- 
tween jalap  and  scammony  resin. — London  Pharm.  Jour.,  May, 
1865. 
LIQUEFACTION  OF  PROTOXIDE  OF  NITROGEN. 
One  of  the  most  interesting  objects  at  a  recent  soiree  at  the 
Paris  Observatory  consisted  in  the  exhibition  of  the  liquefaction 
of  laughing  gas,  the  protoxide  of  nitrogen,  by  M.  Bianchi.  This 
took  place  at  zero  centigrade  under  a  pressure  of  thirty  atmos- 
pheres, the  fluid  issuing  in  a  small  jet  from  a  strong  metallic 
reservoir.  Received  in  a  glass  tube,  it  retained  its  liquid  condi- 
tion by  reason  of  the  depression  of  temperature  produced  by 
evaporation,  so  that  mercury  being  introduced  solidified,  and 
could  be  hammered  like  lead.  Simultaneously,  a  body  in  the 
state  of  ignition,  plunged  into  the  atmosphere  of  the  liquid,  in 
which  the  mercury  froze,  burnt  with  a  brilliant  light.  On  pour- 
ing the  protoxide  into  a  small  platinum  capsule  heated  to'redness, 
