528     A  NEW  METHOD  OF  ESTIMATING  SULPHURIC  ETHER. 
dissolved,  giving  a  yellowish  solution,  which,  on  evaporation,  left 
a  reddish-yellow  residue,  the  greater  part  of  which  was  soluble 
in  ether.  The  etherial  solution  left  an  uncrystallizable  residue 
of  an  amber  color,  and  with  a  very  bitter  taste. 
In  subsequent  experiments  made  by  exposing  santonine  to 
light  under  water  from  which  all  air  had  been  carefully  expelled, 
the  author  obtained  exactly  the  same  results,  and  hence  con- 
cluded that  by  exposure  to  solar  light,  santonine  is  changed  into 
formic  acid,  and  an  uncrystallizable  substance  much  more  soluble 
in  alcohol  and  ether  than  santonine  itself,  and  also  a  red  resinous 
substance.  To  the  yellow  uncrystallizable  substance  he  has 
given  provisionally  the  name  photo-satonic  acid. 
The  acid,  on  analysis,  gave  results  which  agree  very  nearly 
with  the  formula  C22Hi404.  Its  chemical  properties  will  be  de- 
scribed in  a  future  memoir. — Lond.  Chem.  News,  from  Bui.  de 
la  Socitte  de  Paris,  July,  1864. 
A  NEW  METHOD  OF  ESTIMATING  SULPHURIC  ETHER. 
By  MM.  Regnauld  and  Adrian. 
The  purity  of  ether  is  commercially  estimated  by  its  density, 
but  this  is  not  a  rigorous  mode  of  determination,  since  it  is  dis- 
puted what  instrument  is  to  be  used.  There  is  also  the  incor- 
rectness in  the  graduation  of  commercial  instruments,  and,  more- 
over, the  temperature  is  not  taken  into  account. 
Some  degree  of  regularity  is  attained  by  using  a  gravimeter, 
but  by  itself  this  determination  is  insufficient,  since  the  ether  is 
mixed  at  the  same  time  with  water  and  alcohol  in  variable  pro- 
portions. 
The  first  step  towards  obtaining  a  correct  estimate  is  to  sim- 
plify the  nature  of  this  complex  product. 
Having  ascertained  that  carbonate  of  potassa  completely  de- 
hydrated ether,  the  authors  found  that  the  same  salt  brought 
alcohol  mixed  with  the  ether  to  98°  centesimal  without  going 
beyond. 
These  points  established,  they  base  their  process  on  the  esti- 
mation of  the  degree  of  purity  of  ether  by  determining  its  densi- 
ty before  and  after  the  action  of  dry  carbonate  of  potash.  They 
