406 
BENZOIN  AND  BENZOIC  ACID. 
latter.  But  at  temperatures  below  the  boiling  of  bisulphide  of 
carbon,  4  to  5  p.  of  it  are  sufficient  for  dissolving  1  p.  chloral 
hydrate.  If  allowed  to  cool  slowly,  beautiful  crystals  often  an 
inch  in  length  are  obtained,  easily  collected,  and  readily  freed 
from  the  last  traces  of  the  solvent  by  exposing  them  in  thin 
layers  to  the  air.  Thus  obtained,  chloral  hydrate  possesses  no 
acid  reaction  and  does  not  attract  moisture.  The  best  prisms 
begin  ^to  fuse  at  49°  C,  larger  quantities  at  53  to  54°  C,  the 
fused  mass  congealing  again  at  34°,  or  at  40°  C.  if  a  few  crys- 
tals had  remained  unfused.  Samples  not  well  crystallized  fuse 
at  a  lower  temperature.  The  boiling  point  is  97*5°  C.  if  the 
entire  thermometer  is  surrounded  by  the  vapors. 
Bisulphide  of  carbon  is  cheap.  Some  loss  is  unavoidable  ;  im- 
purities in  the  mother-liquor  increase  gradually  to  such  an  ex- 
tent that  a  rectification  of  the  bisulphide  over  corrosive  subli- 
mate becomes  necessary.  With  the  last  portions  of  the  solvent 
a  little  chloral  hydrate  evaporates  from  the  crystals,  but  the  loss 
from  that  source  is  insignificant,  J  grm.  having  lost  but  3-8  per 
cent,  in  nine  days.  A  draft  of  cold  air,  the  addition  of  some 
petroleum  ether,  and  the  employment  of  the  centrifugal  machine 
will  be  of  service  when  operating  on  a  large  scale.  The  price  of 
chloral  hydrate  ought  not  to  be  raised  in  consequence  of  such 
purification.— iV'.  Jahrh.  f.  Pharin.,  1870,  April,  200—204. 
J.  M.  M. 
ON  BENZOIN  AND  BENZOIC  ACID. 
By  Julius  Loewe. 
To  determine  whether  benzoic  acid  exists  free  in  benzoin,  or 
whether  it  is  generated  by  heating  the  resin,  the  author  sought 
to  answer  the  following  four  queries  :  1.  Does  benzoic  acid  exist 
ready  formed  in  benzoin  ?  2.  Is  benzoic  acid  in  the  resin  united 
with  a  base  ?  3.  Is  benzoic  acid  formed  through  the  influence 
of  the  air  upon  the  fused  resin  ?  4.  Is  benzoic  acid  a  product 
of  decomposition  of  a  body  contained  in  the  resin? 
A  larger  quantity  of  benzoin  was  intimately  mixed.  Three 
portions  of  it,  each  weighing  15  grm.,  were  heated  in  the  usual 
manner,  in  a  dish  covered  with  paper,  one  in  contact  with  the 
air,  one  in  a  current-  of  hydrogen  and  the  third  in  carbonic  acid ; 
