470 
rochleder's  proximate  analysis. 
has  been  proved  by  careful  investigation  to  belong  to  the  class  of  copulated 
carbohydrates — as,  for  example,  salicine,  phloridzine,  populine,  arbutine, 
ononine,  sesculine,  &c.  It  is,  therefore,  our  problem  to  ascertain  whether 
the  crystals  in  question  belong  or  not  to  this  class  of  bodies — that  is, 
whether  by  acids  (when  these  do  not  act  in  a  too  concentrated  form  at 
high  temperatures]  they  are  split  into  two  products,  one  of  which — a  car- 
bohydrate— is  in  the  majority  of  cases  sugar,  or  a  similarly  composed  body. 
By  the  action  of  alkalies  on  these  bodies,  two  products  likewise  result — one 
which  is  in  exceptional  instances  sugar,  but  in  the  majority  of  cases  a  car- 
bohydrate, with  properties  different  to  those  of  sugar.  Frequently  the  salt 
of  an  acid  results,  and  a  product  which  is  decomposed  by  acids  into  two 
products,  one  of  which  is  sugar. 
To  ascertain  whether  a  copulated  carhoJiydrate  of  thai  kind  is  present,  the 
crystals  under  examination  are  treated  in  the  following  manner  : — 
They  are  dissolved  in  the  smallest  possible  quantity  of  water,  and  the 
solution  is  mixed  with  a  small  quantity  of  strong  hydrocliloric  acid,  the  acid 
solution  is  introduced  into  a  flask,  and  the  air  drawn  out  by  a  stream  of 
carbonic  acid  gas.  The  flask  is  heated  on  a  sand-bath  until  its  contents 
boil.  To  intercept  the  volatile  products  of  decomposition  perhaps  evolved, 
the  flask  is  connected  with  a  refrigeratory  apparatus  and  a  receiver.  In 
many  cases  while  heating,  and  in  others  after  cooling,  the  fluid  boiled  for 
some  time  deposits  a  product  of  the  decomposition  sometimes  in  the  form 
of  distinct  crystals,  sometimes  in  the  form  of  amorphous  flocks,  or  in  a  state 
of  powder.  Occasionally  a  dense  oily  or  resinous  mass  is  deposited,  which 
sometimes,  after  long  standing,  becomes  crystalline.  When  an  insoluble  or 
difficultly  soluble  decomposition  product  is  separated  after  the  fluid  has 
cooled,  this  is  collected  on  a  filter.  It  is  advisable  to  cool  the  fluid  down  to 
32°  Fahr.,  to  eff'ect  thereby  a  more  complete  separation.  The  filtered  acid 
fluid  is  then  mixed  with  freshly  precipitated  moist  carbonate  of  lead,  until, 
upon  the  addition  of  this  salt,  no  more  effervescence  takes  place.  The 
solution  containing  the  chloride  of  lead  in  solution,  together  with  the 
undissolved  chloride  of  lead  is  poured  into  a  basin,  heated  on  a  water,  bath, 
and  in  small  \)OYt\o\-\s  freshly  prepared  or  still  moist  white  lead  is  added.  A 
basic  lead  salt  of  very  slight  solubility  results.  As  soon  as  by  the  addition 
of  a  fresh  quantity  of  white  lead  no  more  change  is  remarked,  the  contents 
of  the  basin  are  placed  on  a  filter.  The  filtered  fluid  is  mixed  -with  phos- 
phate of  silver,  which  is  prepared  by  precipitating  a  solution  of  phosphate 
of  soda  of  the  Pharmacopoeias  with  a  solution  of  nitrate  of  silver,  and  which 
is  preserved  i7ia  moist  state,  excluded  from  the  light.  As  soon  as  the  phos- 
phate of  silver  and  the  dissolved  chloride  of  lead  come  into  contact  with 
one  another,  they  are  decomposed  into  insoluble  chloride  of  silver,  and 
into  insoluble  phosphate  of  lead.  The  phosphate  of  silver  is  consequently 
added  until  the  yellow  color  of  the  silver  salt  no  longer  disappears  ;  the 
precipitate  in  the  fluid  thus  assumes  a  yellowish  color.  The  fluid  is  filtered 
from  the  precipitate,  which  is  washed.    The  filtered  fluid,  together  with  the 
