288 
Emulsions. 
Am.  Jour.  Pharm, 
June,  1881. 
quantities  of  gum  is  entirely  overcome  by  performing  the  process  as 
directed  in  third  method.  I  emulsified  in  this  way  castor  oil  and  cod 
liver  oil,  the  former  with  four  scruples  and  the  latter  with  one  drachm 
of  gum  arabic  to  the  ounce. 
2.  The  operator  may  add  the  remainder  of  the  water  to  an  emulsion 
made  according  to  the  third  method  in  any  manner,  while,  when  made 
according  to  the  second  method,  care  must  be  taken  not  to  pour  too 
much  water  in  at  once,  as  it  is  apt  to  spoil  even  then  a  carefully  made 
emulsion. 
In  summing  up  these  facts,  I  consider  that  emulsification  is  best 
performed  by  triturating  the  gum  arabic  with  the  oil  and  then  adding 
the  water,  because  even  the  inexperienced  operator  will  hardly  fail  to 
succeed  ;  and,  last  but  not  least,  it  takes  far  less  time. 
The  relative  quantity  of  gum  arabic  and  oil  to  be  used  are  in  their 
best  proportions  when  two  parts  of  the  oil  are  emulsified  with  one 
part  of  gum  arabic.  The  clicking  sound,  which  is  heard  Avhen  an 
emulsion  is  nearing  its  completion,  and  which  is  the  most  certain  sign 
of  having  succeeded,  is  loudest  when  the  ingredients  have  been  used 
in  this  proportion.  Besides  this  clicking  sound,  the  fact  of  the  emul- 
sion being  a  success  may  be  inferred  from  the  fact  that  the  inside  of 
the  mortar  is  continually  and  completely  moistened  with  a  milk-like 
covering  of  a  permanent  character.  If,  however,  drops  of  oil  appear 
on  the  surface  and  the  liquid  in  running  down  the  sides  of  the  mortar 
leaves  them  as  if  they  had  been  moistened  with  water  only,  the  emul- 
sion is  on  the  point  of ''cracking,"  as  the  technical  term  that  is  applied 
to  a  spoiled  emulsion  styles  it.  When  this  occurs  some  mucilage  may 
be  added,  which  will  often  have  the  desired  effect ;  but  trying  to 
improve  a  cracked  emulsion  is  seldom  of  much  avail,  as  it  never  affords 
an  elegant  and  stable  preparation.  It  may  be  done,  however,  by 
making  a  small  quantity  of  a  new  emulsion  and  incorporating  the 
spoiled  one  gradually. 
B.  Gum  Tragacanth. — In  using  gum  tragacanth  for  emulsifica- 
tion I  adopted  a  plan  somewhat  different  from  that  which  is  followed 
when  gum  arabic  is  the  binding  medium.  I  triturated  -^^  part  of  the 
gum  with  one  part  of  water,  then  added  two  parts  of  oil  together  with 
another  part  of  water  and  stirred  until  the  emulsion  was  formed. 
This  method  of  manipulating  gave  very  satisfactory  results. 
Gum  tragacanth  is,  how^ever,  not  often  employed,  but  would  be  a 
well-adapted  binding  medium  for  a  50  per  cent,  emulsion  of  cod  liver 
