268  PREPARATION  OF  SOAP  FOR  SOAP  LINIMENT. 
THE  PREPARATION  OF  SOAP  FOR  SOAP  LINIMENT. 
By  0.  H.  Wood,  F.C.S. 
The  process  given  in  the  British  Pharmacopoeia  for  the  pre- 
paration of  linimentum  saponis  is,  I  believe,  founded  upon  the 
results  of  some  experiments  communicated  to  the  Society  by  Mr. 
Deane  in  1859.  Mr.  Deane  found  that  when  good  Castile  soap  is 
macerated  in  the  spirit  at  a  temperature  below  70°  F.,  the  oleate 
of  soda  dissolves,  while  the  margarate  of  soda  remains  to  a  great 
extent  insoluble,  and  the  resulting  solution  does  not  lose  its 
limpidity  by  the  application  of  moderate  cold.  If,  on  the  con- 
trary, the  whole  of  the  soap  be  dissolved  by  digestion  with  heat, 
the  liniment  gelatinizes  on  a  reduction  of  temperature.  From 
this  it  follows  that  good  soap  liniment  should  consist  of  a  solu- 
tion of  oleate  of  soda,  as  free  as  possible  from  the  alkaline  mar- 
garate or  stearate.  Hence  Castile  soap,  which  is  prepared  from 
olive  oil,  is  the  only  commercial  soap  adapted  to  the  purpose,  the 
other  soaps  being  made  from  solid  fats,  and  containing  a  much 
smaller  proportion  of  the  oleate.  Mr.  Squire  mentions  in  his 
book  an  experiment  indicating  that  white  Castile  soap  is  soluble 
to  the  extent  of  80  per  cent,  in  cold  rectified  spirit.  This  is  the 
soap  described  in  the  Pharmacopoeia,  and  I  have  no  doubt  that 
if  the  process  there  given  for  preparing  the  liniment  be  carefully 
followed,  it  yields  a  sufficiently  satisfactory  result.  Nevertheless, 
if  a  soap  could  be  obtained  containing  a  still  larger  proportion 
of  the  soluble  constituent,  it  would  doubtless  be  preferred.  For 
some  time  past  I  have  prepared  such  a  soap  for  myself  by  a  very 
ready  method,  and  have  found  it  to  possess  considerable  advan- 
tages. 
To  produce  a  soap  as  rich  as  possible  in  oleate  of  soda,  an  oil 
should  be  selected  containing  the  largest  proportion  of  olein  and 
the  smallest  quantity  of  solidifiable  constituents.  Almond  oil  is 
therefore  better  suited  for  the  purpose  than  olive  oil,  and  it  is 
from  this  material  that  I  obtain  my  product. 
The  saponification  of  oil  as  commonly  performed  is  a  protrac- 
ted and  somewhat  tedious  process  to  conduct  on  the  small  scale. 
For  this  reason,  probably,  chemists  are  not  in  the  habit  of  pre- 
paring their  own  soap.    But  if,  instead  of  boiling  the  oil  and 
