PURIFICATION  OF  CHLORAL  HYDRATE. 
'405 
of  conia  between  the  unripe  fruits  from  first  and  second  years' 
plants. — Ibid.  261,  from  Wien.  arztl.  Wochenbl.  1870,  1. 
PURIFICATION  OF  CHLORAL  HYDRATE. 
By  Dr.  F.  A.  Fluckiger. 
The  author  refers  to  Rieckher's  and  Hager's  observations,* 
regarding  reliable  tests  for  the  purity  of  this  medicinal  agent,  but 
he  objects  to  its  employment  unless  it  be  in  well  formed  separate 
crystals.  Though  as  met  with  in  commerce  it  is  usually  of 
good  quality,  the  crystalline  masses  or  imperfect  fractions  of 
crystals  are  unsightly  in  appearance  and  frequently  possess  a 
stinging  odor,  and  readily  absorb  moisture ;  qualities  which  are 
due  to  its  insufficient  purification  on  a  large  scale.  The  last 
traces  of  impurity  cannot  be  removed  by  fusing  and  redistilling 
it,  and  its  appearance  is  not  improved  by  this  operation.  This 
purpose  is  effected  solely  by  recrystallization. 
There  is  perhaps  scarcely  a  liquid  in  which  chloral  hydrate  is 
insoluble  at  ordinary  temperature ;  four  parts  of  it  dissolve 
gradually  in  one'part  of  water,  the  solution  crystallizes  at  0°  0., 
but  not  in  well  formed  crystals.  Alcohol  and  ether  dissolve  it 
to  such  an  extent  that  it  likewise  does  not  crystallize  well  on 
evaporating  these  solvents  ;  absolute  alcohol  must  be  excluded 
because  it  combines  with  chloral. f 
Chloroform  and  benzole  are  well  adapted  for  recrystallization, 
but  the  first  is  too  dear  and  the  last  cannot  be  entirely  removed 
from  the  crystals.  The  same  holds  good  for  oil  of  turpentine, 
from  which  most  beautiful  tables  and  laminae  are  obtained,  if 
1  p.  chloral  hydrate  is  dissolved  in  from  five  to  six  parts  of  the 
oil  at  from  30  to  40°  C,  and  the  solution  allowed  to  cool  slowly. 
Fat  oils,  which  dissolve  it  readily,  are  evidently  not  adapted  for 
this  purpose.  From  petroleum  ether,  which  at  a  moderate  heat 
dissolves  much  chloral  hydrate,  it  crystallizes  well  on  cooling, 
but  too  rapidly  to  admit  of  large  prisms  being  obtained ;  on  a 
large  scale,  however,  it  may  be  of  better  service. 
Uniformly  satisfactory  results  were  obtained  with  bisulphide 
of  carbon.  45  parts  of  it  dissolve  at  15  to  18°  C.  but  1  p.  choral 
hydrate  ;  it  precipitates  ethereal  and  alcoholic  solutions  of  the 
*  Amer.  Jour.  Pharm.,  1870,  p.  238.     f  L.  c.  p.,  239. 
I 
