rochleder's  proximate  analysis. 
46T 
It  was  mentioned  previously  that  sometimes  crystals  will  separate  from 
the  residues,  which  by  the  evapor.ition  of  the  water  or  the  spirit  are  left  be- 
hind, and  that  these  crystals  should  be  removed  from  the  mother  liquors 
from  which  they  have  separated. 
"When  the  crystals  have  been  separated  from  the  mother  liquors,  their 
degree  of  solubility  must  first  be  ascertained.  That  they  are  soluble  in 
water  is  evident  from  their  method  of  preparation,  although  they  may  be 
difi&cultly  soluble  in  water.  The  presence  of  other  substances  in  the 
watery  decoction  may  considerably  increase  their  solubility  in  water.  If 
the  same  crystalline  mass  had  had  formed  from  the  residues  which  were 
obtained  from  the  watery  decoction  by  the  salts  of  lead  as  from  the  residues 
which  remained  after  the  treatment  of  the  watery  decoction  by  alum 
and  ammonia,  it  results  that  this  crystalline  mass,  which  may  be  one  body 
or  a  mixture  of  several  substances,  is  quite  as  soluble  in  alcohol  as  in 
water,  because,  had  it  been  insoluble  in  alcohol,  it  would  have  been  left 
behind  on  separating  the  sulphates  of  potash  and  ammonia  by  anhydrous 
alcohol,  with  these  sulphates  as  an  insoluble  body.  It  still  remains  to  be 
ascertained  whether  the  crystalline  mass  is  quite  or  partially  soluble  in 
ether,  as  well  as  whether  acidulated  water  dissolves  more  of  it  than  pure 
water.  When  the  degree  of  solubility  has  been  learnt  by  these  experi- 
ments, a  method  is  afforded  which  had  to  be  found  to  purify  the  still  im- 
pure crystals  by  recrystallization  before  they  are  further  investigated. 
We  first  ascertain,  with  a  very  small  quantity  of  ih^  crystals  purified 
by  recrystallization,  whether  they  can  be  partially  or  entirely  sublimed  or 
not,  altered  or  unaltered.  The  experiment,  which  gives  in  most  instances 
a  negative  result,  can  be  performed  between  two  small  watch  glasses 
fitted  to  one  another. 
To  arrive  at  the  nature  of  these  crystals,  we  proceed  further,  in  the  fol- 
lowing manner : — 
We  first  ascertained  whether  an  organic  base,  or  a  mixture  of  several  or- 
ganic bases,  as  an  acetate  or  acetates,  is  contained  in  the  crystalline  mass. 
To  detect  these  bodies,  a  portion  of  the  separated  crystals  is  employed,  and 
this  is  divided  into  four  equal  parts. 
The  first  part  is  dissolved  in  the  smallest  required  quantity  of  water, 
and  a  few  drops  of  hydrochloric  acid  are  added  to  the  solution,  then  bichlo- 
ride of  platina.  If  no  precipitate  ensues,  a  little  anhydrous  alcohol  is 
added,  and  then  if  no  precipitate  results,  a  small  quantity  of  ether.  The 
resulting  precipitate  (if  any)  is  separated  by  a  filter  from  the  fluid,  and 
washed  with  a  mixture  of  anhydrous  alcohol  with  a  little  ether.  The  dried 
precipitate  is  tested,  to  ascertain  whether  it  contains  potassa  or  not,  by  heat- 
ing it  to  redness,  and  extracting  the  platina  residue  with  water,  and  testing 
for  the  potash  therein,  which  must  be  present  as  chloride  of  potassium  if 
the  crystals  contained  potash.  It  is  well  to  examine  the  portion  of  crys- 
tals  employed,  to  learn  their  capacity  for  sublimation,  to  ascertain  whether 
the  residue  generally  remaining  will  burn  completely,  and,  when  it  leaves 
an  ash,  whether  potassa  is  present  therein. 
