468 
rochleder's  proximate  analysis. 
The  second  part  of  the  solution  is  mixed  with  a  solution  of  bichloride  of 
mercury.  By  this  means  there  are  several  bases  precipitated — for  example, 
emetia,  &c 
The  third  2Jari  of  the  solution  is  mixed  with  a  concentrated  solution  of 
caustic  soda  in  very  small  quantity.  If  the  crystals  were  the  acetate  of  a 
base  difficultly  soluble  in  water,  or  if  they  contained  a  little  of  one  or  several 
such  salts,  the  base  would  be  precipitated  from  its  concentrated  solution 
by  the  alkali,  after  the  neutralization  of  the  acetic  acid.  In  an  excess  of 
the  alkali,  the  precipitated  base  is  frequently  more  soluble  than  in  pure 
water,  therefore  the  alkali  must  only  be  added  by  drops.  Instead  of  caus- 
tic soda,  carbonate  of  soda  can  be  employed. 
The  fourth  part  of  the  solution  is  heated  after  tlie  addition  of  an  allcali, 
and  it  is  ascertained  whether  the  vapor  thereby  evolved  is  alkaline.  Such 
a  vapor  may  result  when  a  volatile  base  is  present  whose  acetate  is  crys- 
tallizable,  or  when  Uie  crystals  were,  or  contained  a  body  analogous  to, 
asparagine  :  in  the  latter  case,  ammonia  is  evolved  under  the  given  condi- 
tions. 
According  to  researches  of  Sonnenschein,  phosphor-molybdic  acid  is  a 
good  test  to  prove  the  presence  of  bases.  It  gives  with  all  bases,  almost 
without  exception,  precipitates  as  well  with  the  oxygenated  as  the  non- 
oxygenated  ones  ;  these  are  generally  yellow,  but  sometimes  colored  brown- 
ish yellow.  This  compound  is  prepared  by  precipitating  molybdate  of 
ammonia  with  c  phosphate  of  soda,  suspending  the  well-washed  precipi- 
tate in  water,  and  heating  it  with  carbonate  of  soda,  until  it  is  completely 
dissolved.  This  solution  is  evaporated  to  dryness,  and  then  heated  to 
redness,  for  the  complete  expulsion  of  the  ammonia.  If  the  molybdic  acid 
is  thereby  partially  reduced,  the  heated  residue  is  moistened  with  nitric, 
acid,  and  again  heated  to  redness.  The  resulting  dry  saline  mass  is  heated 
with  water,  nitric  acid  is  added  to  produce  a  strong  acid  reaction,  and 
then  with  so  much  water  mixed,  that  ten  parts  of  the  solution  contain  one 
part  of  the  dry  saline  mass.  This  golden  yellow  fluid,  after  filtration, 
must  be  preserved,  excluded  as  much  as  possible  from  the  influence  of  am- 
moniacal  vapors. 
If  we  have  found  by  this  examination  whether  basic  bodies  are  present 
or  not,  it  is  necessary,  in  the  case  of  I)ases  being  present,  to  ascertain 
whether  one  or  more  bases  are  at  tJie  same  time  present. 
Many  vegetable  substances  contain  only  a  single  base.  The  berries  and 
leaves  of  coffee  contain  only  caffeina,  the  berries  of  cocoa  only  theobromina, 
&c.  But  in  cinchona  bark,  quinia  and  cinchonia  are  present ;  in  the  strych- 
nej»,  brucia  and  strychnia,  besides  another  base.  The  papaveracese  con- 
tain at  the  same  time  three  or  more  bases. 
By  the  investigation  of  the  degree  of  solubility,  the  opportunity  has  in 
many  cases  been  given  to  learn  whether  we  have  to  do  with  one  or  several 
bodies.  To  arrive  at  certainty  on  the  point,  the  following  method  of  ex- 
amination is  preferable  to  all  others,  which  is  founded  on  a  discovery  made 
