552 
ON  SEBACIC  ACID. 
at  the  true  standard  of  strength  of  the  several  pharmaceutical 
preparations  containing  prussic  acid.  A  test  solution  of  iodine, 
of  a  definite  strength,  is  then  prepared  (three  grains  to  the  ounce 
answers  very  well,)  which  may  be  put  into  a  Gay-Lussac's  pouret, 
from  which  it  is  dropped  into  a  certain  quantity  of  the  liquid 
under  examination,  till  a  permanent  yellowish  tinge  becomes 
visible,  when  the  quantity  employed  is  read  off  from  the  graduated 
scale  and  the  strength  of  the  preparation  at  once  determined. 
The  process  gives  not  only  the  comparative  value  but  the  actual 
per  centage  of  hydrocyanic  acid  present,  as  every  equivalent  of 
cyanogen  absorbs  one  equivalent  of  iodine.  I  have  found  this 
process  of  great  practical  utility,  and  recommend  it  for  the  adop- 
tion of  my  fellow  Pharmaceutists. — Pharm.  Joum.,  Sept.,  1853. 
ON  SEBACIC  ACID. 
Br  Henri  Carlet. 
Since  the  discovery  of  sebacic  acid  by  Thenard,  this  acid  has 
always  been  prepared  by  the  process  indicated  by  that  illustrious 
chemist,  that  is  to  say,  by  the  distillation  of  fat.  This  process 
only  gives  small  quantities  of  sebacic  acid  ;  consequently  the 
properties  of  this  acid  and  of  its  compounds  have  been  but  little 
studied.  In  his  researches  upon  castor  oil,  M.  Bonis  has  indi- 
cated a  ready  mode  of  preparing  sebacic  acid  ;  at  the  close  of  his 
investigations  he  had  obtained  a  considerable  quantity  of  it, 
which  he  was  so  good  as  to  place  at  my  disposal.  I  undertook 
this  investigation  with  the  view  of  ascertaining  the  identity  of 
the  acid  obtained  by  the  old  and  new  processes,  and  adding  some 
new  facts  to  its  history. 
The  following  are  the  principal  results  at  which  I  have  ar- 
rived : — 
The  acid  obtained  by  both  processes  is  the  same  substance  ;  its 
composition,  long  since  indicated  by  Dumas  and  Peligot,  is  rep- 
resented by  the  formula  C20H18O8  .  The  average  of  five  analyses 
of  sebacic  acid  gave  me  C  =  59-25,  II  =  9-07  per  cent. 
Sebacic  acid  in  a  state  of  purity  is  white,  solid,  and  fusible  at 
261°  F.  The  density  of  the  fused  acid  is  1-1317.  It  is  spar- 
ingly soluble  in  cold,  but  very  soluble  in  hot  water ;  it  is  also 
very  soluble  in  alcohol,  ether,  and  fatty  bodies.    Chlorine  acts 
