ON  CROTON  OIL. 
411 
acid  and  acrylic  acid.  As  angelicic  acid,  when  fused  with 
potash,  furnishes  acetic  and  propionic  acids,  so  crotonic  acid 
gives  2  equivs.  acetic  acid. 
C8  H6  04+2KH02=2C4  H3  K04+2H. 
Crotonic  acid  occurs  with  angelicic  acid,  after  the  saponifi- 
cation of  the  oil  with  solution  of  soda,  in  the  nearly  black 
subjacent  fluid.  This  is  distilled  with  tartaric  acid ;  the  distillate 
is  saturated  with  baryta,  and  evaporated,  the  baryta-salt  is 
again  distilled  with  dilute  tartaric  acid,  and  this  is  repeated 
until  the  distillate  passes  over  free  from  muriatic  acid  ;  lastly, 
the  neutral  baryta-salt  is  prepared,  and  the  dry  salt  is  heated 
with  a  solution  of  phosphoric  acid  of  such  strength  that  it  boils 
at  226Q«4  F.  The  crotonic  acid  then  separates  as  a  limpid 
liquid,  and  floats  on  the  surface  of  the  fluid. 
The  crotonates  of  potash  and  soda  are  deliquescent.  The 
baryta-salt  is  readily  soluble,  and  forms  an  amorphous,  white 
mass  ;  it  always  smells  like  the  free  acid. 
The  above-mentioned  soluble  salts  gave  precipitates  with 
many  metallic  compounds ;  at  the  same  time  the  odor  of  the 
free  acid  was  almost  always  perceptible,  which  may  be  due  to 
the  partial  formation  of  basic  salts.  With  protosalts  of  iron, 
brownish-yellow  precipitates  are  produced ;  persalts  of  copper 
form  pale  blue  precipitates,  which  appear  nearly  white  in  small 
quantities.  The  analysis  of  a  precipitated  copper-salt,  dried 
in  vacuo  over  sulphuric  acid,  gave  the  proportion  1  Cu  to  5-7C. 
Solutions  of  lead,  mercury  and  silver  gave  white  precipitates. 
A  precipitate  formed  by  nitrate  of  silver  and  crotonate  of  baryta 
was  amorphous  and  white  when  dried ;  it  became  brown,  slowly, 
when  exposed  to  the  sun,  more  rapidly  at  212°  F.,  and  was 
tolerably  soluble  in  hot  water. 
Crotonate  of  Silver,  C8  H5  AgO4,  obtained  by  boiling  the 
aqueous  distillate  from  the  baryta-salt  and  tartaric  acid  with 
oxide  of  silver,  was  crystallized,  and  gave  on  analysis — 
c 
24-57 
24-40 
8: 
=  48 
24-87 
H 
2-62 
2-80 
5 
5 
2-59 
Ag 
55-90 
56-13 
1 
108 
55-95 
0 
16-91 
16-67 
4 
32 
15-59 
The  active  matter  of  croton  oil,  to  which  the  author  gives  the 
name  of 
