Am.  Jour.  Pliarm.  \ 
June,  1881.  j 
Emulsions. 
287 
thick,  adding  water  and  oil  alternately.  I^astly  the  remainder  of  the 
W'ater  is  gradually  incorporated. 
Second  Method. — One  part  of  gum  arable  is  triturated  with  two 
parts  of  oil,  then  one  and  a  half  part  of  water  is  poured  in  at  once, 
the  mixture  stirred  briskly  until  the  emulsion  is  formed  and  then 
•diluted  with  the  remainder  of  the  water. 
After  a  series  of  careful  experiments,  I  propose  the  following 
method  as  giving  the  most  satisfactory  results  and  call  it  the 
Third  Method} — Take  one  part  of  gum  arable,  triturate  it  with  two 
•or  more  parts  of  oil,  then  add  two  parts  of  water  at  once,  stir  briskly 
until  the  emulsion  is  formed,  lastly  add  the  remainder  of  the  water. 
The  difference  between  the  second  and  third  method  is,  that  in  the 
latter  two  parts  of  water  are  always  to  be  taken  to  one  part  of  gum 
arable,  independent  of  tlie  quantity  of  oil  used. 
With  these  three  methods  I  have  succeeded  in  making  perfect  and 
stable  emulsions,  but  a  number  of  carefully  conducted  experiments 
lias  taught  me  that  the  third  is  the  best,  next  in  order  follows  the  sec- 
ond and  then  comes  the  first. 
Advantages  of  the  second  and  th  ird  methods  over  the  first. 
1.  The  making  of  a  smooth  mucilage  of  gum  arable  requires  con- 
siderable more  time  than  triturating  the  gum  with  the  oil.  To  over- 
•€ome  this  difficulty,  some  pharmacists  are  in  the  habit  of  triturating 
the  gum  arable  with  half  its  weight  of  sugar.  But  an  addition  of 
.sug-ar  will  retard  emulsification  to  such  an  extent  that  it  would  be 
saving  time  to  make  the  mucilage  without  the  sugar. 
2.  Emulsification  takes  ])lace  much  more  rapidly  when  adding  the 
water  to  the  mixture  of  gum  and  oil  than  if  the  oil  is  stirred  with  the 
mucilage. 
3.  Essential  oils,  which  are  generally  considered  difficult  of  emulsi- 
fication, are  made  into  emulsions  w^ith  the  greatest  ease  when  using  the 
•second  and  third  methods.  An  emulsion  of  oil  of  turpentine 
iiffbrds  a  striking  illustration  of  this  fact,  which  will  convince  the 
most  skeptical. 
Advantages  of  the  third  method,  over  the  second. 
1.  The  difficulty  of  emulsifying  large  quantities  of  oil  with  small 
^  For  niethods  of  emiilsioniziiig  not  iiientioiiei]  by  the  autlior,  consult 
papers  by  J.  Winchell  Forbes,  "  Amer.  Jour.  Pliar.,"  1872,  p.  Gl ;  L.  v. 
Cotzluuisen,  ibid.,  1878,  p.  284;  and  Ph.  H.  Dil-',  ibid.,  1878,  p.  326.  The 
third  method  is  essentially  that  of  A.  W.  Gerrard,  ibid.,  1S80,  p.  560. — Ed. 
