482 
ON  EMULSIONS. 
pies,  to  lay  down  a  few  general  rules  of  practical  utility  to  the 
pharmaceutist.  I  commenced  work  by  experimenting  upon 
simple  oils  and  water,  without  addition. 
Taking  an  ^iss  phial,  and  putting  into  it  half  an  ounce  distilled 
water,  and  1  drachm  olive  oil ;  shaking  them  together,  and  noting 
the  kind  of  mixture  and  the  time  required  for  separation ;  then 
adding  oil,  drachm  by  drachm, — making  the  observations  till 
there  were  6  drachms  of  oil  to  4  of  water.  Then  commencing 
again  with  4  drachms  of  oil  to  one  of  water,  the  reverse  of  the 
proportions  first  mixed,  repeating  the  observations,  step  by  step, 
as  water  was  added,  drachm  by  drachm,  up  to  4  drachms.  Had 
I  been  able  to  devote  the  requisite  time  to  the  subject,  I  should 
have  made  similar  experiments  with  almond  oil,  castor  oil,  lin- 
seed oil,  balsam  of  copaiba,  and  other  materials,  as  they  suggest- 
ed themselves,  and  then  proceeded  to  ascertain  the  effects  of  in- 
troducing other  chemical  or  mechanical  elements  into  the  opera- 
tion ;  but  the  series  of  observations  which  thus  should  have  been 
counted  by  hundreds,  was  unexpectedly  cut  short  before  it 
reached  the  tenth  of  its  expected  dimensions,  and  I  have  now 
only  to  draw  your  attention  to  two  or  three  points  which  already 
bear  some  interest. 
When  olive  oil  was  added  to  Water,  the  mixture  separated  most 
slowly  when  the  proportion  was  3  drachms  of  oil  to  4  of  water, 
the  time  required  increasing  with  each  drachm  of  oil  up  to  this 
proportion,  and  again  decreasing  with  further  additions,  till  the 
proportion  was  6  of  oil  to  4  of  water.  When  water  was  added 
to  olive  oil,  the  separation  takes  place  much  more  slowly  than  in 
the  former  case  ;  and,  when  it  had  been  added  drachm  by  drachm, 
with  agitation  at  each  step,  till  there  were  equal  parts  of  each, 
the  separation  took  place  only  in  several  hours,  instead  of  as 
many  minutes,  which  had  sufficed  in  the  former  case.  And  there 
was  no  less  difference  in  the  mixing  than  in  the  separating.  In 
the  first  series  the  mixing,  as  far  as  the  fluids  seemed  likely  to 
mix,  was  effected  by  a  few  seconds  of  brisk  agitation  ;  but,  in  the 
second  series,  a  quarter  of  an  hour's  agitation  or  more  was  re- 
quired to  effect  the  mixture  of  the  third  and  fourth  drachm  of 
water,  and,  when  it  did  take  place,  the  mixture  became  so  thick, 
that  it  would  not  rattle  when  the  bottle  was  violently  shaken. 
