EMULSIONS  OF  OILS  AND  FATS  BY  CARBONATES  461 
in  excess  or  not,  whether  added  to  a  strong  or  a  weak  solution, 
a  yellow  white  curdy  precipitate  falls.  If  a  very  gentle  heat 
be  now  applied,  this  precipitate  dissolves,  but  as  the  liquid  cools 
again,  a  crop  of  yellow  (gold-yellow)  crystals  falls  so  abundantly 
as  sometimes  to  give  a  gelatinous  appearance  to  their  mass. 
These  crystals  are  flat  plates,  cuneiform  in  shape,  a  pure  lemon- 
yellow  in  color,  and  superimposed  one  upon  the  other  in  the 
same  way  as  are  crystals  of  nitrate  of  urea.  The  crystals  are 
best  observed  under  a  low  magnifying  power,  fifty  diameters, 
and  will  then  be  found  such  as  we  have  described  them.  The 
precipitate  is  not  soluble  in  excess  of  ferrocyanid  of  potassium, 
but  like  this  latter  is  decomposed  by  boiling  with  mineral  acids., 
This  test  for  cinchonia  is  a  very  delicate  one,  not  less  so  than 
that  by  the  biniodid  of  potassium,  and  is  far  more  characteristic, 
since  none  of  the  alkaloids  manifest  the  reaction  except  cin- 
chonia. In  practice  it  will  be  well,  for  obvious  reasons,  to  use 
a  slight  excess  of  ferrocyanid  of  potassium,  as  little  excess  of 
acid  as  possible,  and  to  heat  the  liquid  very  gently  after  the  first 
precipitate  has  fallen  Silliman's  Amer.  Journ.,  July,  1858. 
EMULSIONS  OF  OILS  AND  FATS  BY  CARBONATES. 
The  following  conclusions,  which  Messrs.  Jeannel  and  Mousel 
have  derived  from  their  investigations,  are  of  some  importance 
in  a  therapeutic  point  of  view  :  ( Union  Medio. — Med.  Neuigh. } 
1.  All  inorganic  or  organic  fluids  of  alkaline  reaction  form 
emulsions  with  oily  substances  in  distilled  water  ;  strong  insoluble 
metallic  bases  have,  to  some  extent,  the  same  effect.  2.  The 
process  of  emulsion  of  fats  by  bases  is  the  beginning  of  saponifi- 
cation. 3.  5  centigrammes  of  carbonate  of  potash  or  soda  are 
sufficient  to  change  8  grammes  of  oil  with  100  grammes  of  water 
into  a  permanent  emulsion.  The  intensity  of  the  emulsory  for- 
mation is  in  direct  proportion  to  the  intensity  of  alkalescence;  an 
acid  reaction  of  the  fluid  renders  the  formation  of  an  emulsion 
impossible.  4.  The  pancreatic  juice  contributes  most  to  the  diges- 
tion of  fats,  because,  of  all  digestive  fluids,  it  presents  the  strongest 
alkalescence  ;  the  other  alkaline  digestive  fluids  sometimes  replace 
it.  5.  The  introduction  of  a  moderate  quantity  of  alkali  in  the 
stomach,  sufficient  to  blunt  the  acidity  of  the  chyme,  or  merely 
