Am-DJe°cu^arm-}  Oleates.  595 
Acidum  Oleicum  is  stated  by  the  U.  S.  Pharmacopoeia  to  have  a 
specific  gravity  0*800  to  0*810.  The  U.  S.  Dispensatory,  page  89, 
states  that  this  is  an  error,  and  should  be  0  900  to  0*910.  Gmelin 
(vol.  xvii,  p.  64)  quotes  Chevreul  as  authority  for  specific  gravity 
0'898.  The  British  Pharmacopoeia  states  *860  to  '890.  While  Allen 
(Commerc.  Organic  Analysis,  vol.  ii,  p.  233)  states  that  the  pure  acid 
"has  a  density  of  *897  at  19°  C,"  and  calls  attention  to  an  error  in 
Watt,  who  quotes  Chevreul  as  '808  and  says,  "  the  same  mistake  is 
made  by  Wurtz  and  other  industrious  compilers  and  copyists."  The 
oleic  acid  for  pharmaceutical  purposes  need  not  be  a  chemically  pure 
acid.  In  fact,  for  many  oleates,  notably  for  bismuth  oleate,  it  is  desir- 
able to  have  present  a  small  amount  of  stearic  acid.  Purified  red  oil 
answers  admirably  for  all  medicinal  oleates.  According  to  Chas. 
Rice  (Amer.  Jour.  Phar.,  1873,  p.  1),  such  a  purified  acid  exhibits 
a  specific  gravity  of  *895  at  62°  F.  E.  C.  Saunders  (New  Remedies, 
June,  1880),  reports  -897,  while  Dr.  Squibb  (Ephemeris,  1882,  p. 
158)  states  the  specific  gravity  at  *898.  Several  commercial  samples 
recently  examined  showed  specific  gravities  of  0*8991,  0  8992,  0*909, 
at  60°  F.  Another  sample  was  semi-solid  at  60°  F.,  so  the  specific 
gravity  was  taken  at  66°  F.  and  found  to  be  0*8854.  Another  sample 
received  from  the  manufacturer  without  subsequent  purification  had  a 
gravity  of  *8846  at  60°  F.  The  first  and  second  were  light  in  color 
and  contained  but  small  quantities  of  other  acids.  The  third  was  very 
dark  colored  and  the  fourth,  while  of  a  paler  color,  contained  a  large 
excess  of  solid  acids.  These  figures  indicate  that  the  correct  specific 
gravity  should  be  0*890  to  0*900.  The  first  acid  was  the  one  used 
for  the  experiments  here  recorded  : 
Zinci  Okas. 
Oleate  of  zinc,  Zn(C18H3302)2' 
Take  of— 
Oleic  acid  1,000  grains. 
Soda1   160     "  orq.s. 
Alcohol   6  fluidrachms. 
Zinc  sulphate   550  grains. 
Water,  a  sufficient  quantity. 
Warm  the  oleic  acid  in  a  capacious  vessel  on  the  water-bath  to  a 
temperature  of  60°  to  66°  C.  (140°  to  150°  F.),  and  having  dis- 
solved the  soda  in  a  mixture  of  the  alcohol  and  two  fluidounces  of 
1  The  granular  sodar  known  as  Banner  lye,  containing  about  90  per  cent,  of 
soda,  was  found  to  answer  well  for  this  purpose. 
