22 
Goto  Barks. 
(Am.  Jour.  Pharm,, 
t       Jan.,  1880. 
is  obtained  in  large  prisms  or  plates  on  the  slow  evaporation  of  its  solu- 
cion  in  chloroform  or  alcohol.  In  the  latter  case  it  is  occasionally 
obtained  amorphous  and  crystallizes  after  some  time.  It  is  easily 
soluble  in  alcohol,  chloroform,  benzol,  aceton  and  carbon  bisulphide, 
but  is  nearly  insoluble  in  petroleum  naphtha.  .  Cold  water  dissolves 
very  little  cotoin,  but  acquires  a  rather  yellow  color  ;  it  is  somewhat 
more  soluble  in  boiling  water.  Alkalies  and  alkaline  carbonates  dissolve 
cotoin  readily  and  separate  it  again  completely  on  the  addition  of  hydro- 
chloric or  sulphuric  acid.  The  same  solutions  treated  with  carbonic 
acid  gas  deposit  by  far  the  la5;gest  part  of  cotoin,  which  is  also  soluble  in 
potassium  disulphide  and  again  precipitated  by  acids. 
Concentrated  nitric  acid  colors  cotoin  blood-red  ;  on  heating  dis- 
solves it  with  a  blood-red  color,  and  deposits  a  red  resin  on  cooling  or 
on  the  addition  of  water.  Cotoin  dissolves  in  concentrated  sulphuric 
acid  with  a  brown-yellow,  and  in  warm  hydrochloric  acid  with  a  yellow 
color,  and  crystallizes  from  the  latter  solution  unaltered.  The  aqueous 
solution  of  cotoin  has  a  neutral  reaction,  and  reduces  gold  and  silver  salts 
in  the  cold;  it  is  not  precipitated  by  neutral  acetate,  but  yields  a  yellow 
precipitate  with  basic  acetate  of  lead,  and  a  brownish-black  precipitate, 
or  in  dilute  solution  a  brownish-black  color,  with  ferric  chloride.  The 
alcoholic  solution  of  cotoin  is  colored  intensely  brown-red  by  ferric 
chloride,  and  yields,  with  aqueous  solution  of  lead  acetate,  a  yellow 
crystalline  deposit  of  cotoin.  Fehling's  solution  is  reduced  slowly  in. 
the  cold,  but  rapidly  on  heating. 
Cotoin  has  a  burning  acrid  taste ;  its  dust  excites  sneezing  and 
coughing.  It  has  no  action  on  polarized  light.  It  melts  at  I30°C, 
(266°P\)  (if  contaminated  with  even  traces  of  resins  at  a  lower  point),, 
and  congeals  on  cooling  in  a  crystalline  condition.  At  a  higher  tem,- 
perature  it  is  decomposed.  It  is  free  from  water  of  crystallization,  its 
composition  being  represented  by  the  empirical  formula  Q.^^^^O^.  A 
saturated  solution  of  cotoin  in  ammonia  yields  with  lead  acetate  a 
bright-yellow,  amorphous  precipitate  of  trilead  cotoin,  C22Hj2Pb30g. 
When  heated  in  a  sealed  tube  for  tvvo  hours  to  I40°C.  with  strong 
hydrochloric  acid,  benzoic  acid  and  a  little  of  a  red  amorphous  substance 
is  produced.  Benzoic  acid  is  also  produced  on  melting  cotoin  with 
potassium  hydrate,  together  with  a  small  quantity  of  an  oily  substance 
having  a  bitter  almond  odor. 
Tribromcotoin^  CggH^gBrgOg,  is  obtained  by  acting  with  bromine  at  the 
