ACTION  OF  LIGHT  ON  SANTONINE. 
527 
the  solution,  and  secondarily  by  that  solid  matter  being  in  a 
state  of  mechanical  or  chemical  union  with  its  solvent.  We 
should  strongly  recommend  Professor  Guthrie  to  experiment  on 
solutions  of  the  acids,  and  see  the  effect  of  their  definite  hy- 
drates in  altering  the  size  of  drops.  According  to  Graham, 
nitric  acid,  with  three  equivalents  of  water,  is  found  to  have  a 
lower  rate  of  transpiration  than  when  diluted  more  or  less. 
With  sulphuric  acid,  the  maximum  occurs  with  the  monohy- 
drate,  with  acetic  acid,  the  byhydrate  with  hydrochloric  acid, 
the  dodecahydrate  and  so  on.  The  determination  of  the  rela- 
tions, too,  between  the  drop-size,  and  the  boiling  points,  and 
composition  of  the  alcohols,  ethers,  &c,  would  be  most  interest- 
ing. The  influence  of  temperature  also  needs  inquiring  into, 
in  fact,  there  is  an  enormous  and  evidently  most  fruitful  field 
open  to  Professor  Guthrie's  talents  and  patience,  of  both  of 
which  the  present  paper  has  given  us  so  high  an  opinion. — 
Chemist  and  Druggist. 
ACTION  OF  LIGHT  ON  SANTONINE. — PHOTO-SANTO  NIC 
ACID. 
By  M.  Sestini. 
-  Santonine,  it  is  well  known,  is  colored  yellow  by  exposure  to 
solar  light,  and  this  takes  place  in  a  vacuum  as  well  as  in  the  air. 
It  does  not  take  place,  however,  when  the  actinic  rays  are  cut  off 
by  means  of  a  solution  of  nitrate  of  uranium. 
Crystals  of  santonine  reduced  to  powder  and  then  exposed  to 
light,  not  only  change  color,  but  evolve  a  resinous  odor,  and  ac- 
quire a  very  bitter  taste.  Water  added  to  this  changed  santo- 
nine acquires  a  yellow  color,  presents  an  acid  reaction,  and  has 
a  bitter  taste.  On  distillation  the  same  water  yields  an  acid 
liquid,  which  reduces  nitrate  of  silver  and  bichloride  of  mercury, 
and  precipitates  acetate  of  lead  white.  The  author  concluded 
that  the  volatile  matter  formed  during  the  coloration  of  santo- 
nine by  light  was  formic  acid.  On  evaporation  to  dryness  the 
distillate  gives  a  deep  red-colored  resinous  residue. 
By  treatment  with  water  the  colored  santonine  almost  entirely 
lost  its  odor.    On  treatment  with  alcohol,  it  now  in  great  part 
