rochleder's  proximate  analysis. 
561 
(Continued  fiom  page  472.) 
Another  method,  which  in  many  cases  is  easy  of  execution,  depends  on 
the  behaviour  of  many  bodies  to  alumina.  The  hydrochloric  acid  of  the 
fluid  is  precipitated  completely  with  the  solution  of  sulphate  of  silver;  the 
fluid,  now  containing  sulphuric  acid,  is  mixed  with  the  hydrate  of  alumina 
in  a  moist  condition,  and  ammonia  is  added  to  the  solution.  If  a  precipitate 
results  which  contains  the  decomposition  product  obtained  with  sugar  while 
the  sugar  and  sulphate  of  ammonia  and  a  little  free  ammonia  remains 
dissolved  in  the  fluid,  this  solution  is  evaporated,  and  the  residue,  when 
it  has  acquired  a  syrupy  consistence,  is  mixed  with  anhydrous  alcohol. 
The  sulphate  of  ammonia  remains  undissolved,  whilst  the  sugar  is  taken 
up  by  the  alcohol  containing  a  little  water,  and  after  evaporation  remains 
behind. 
If  a  volatile  decomposition  product  results  by  the  treatment  of  the  crys- 
tals with  dilute  hydrochloric  acid  in  the  heat,  this  is  contained  in  the 
receiver  which  was  connected  with  the  flask  by  means  of  a  refrigeratory 
apparatus,  wherein  the  boiling  with  the  acidulated  water  took  place.  A 
small  portion  of  the  fluid  is  mixed  with  carbonate  of  soda  as  long  as  effer- 
vescence results  with  this  salt,  and  is  then  distilled.  If  the  distillate  is 
pure  water,  the  decomposition  product  is  an  acid.  On  the  contrary,  if  the 
decomposition  product  is  not  an  acid,  it  passes  over  by  distillation,  while 
the  hydrochloric  acid  remains  in  the  residue  as  common  salt.  When  an 
acid  has  been  obtained,  to  obtain  it  free  from  hydrochloric  acid  the  distil- 
late is  mixed  with  sulphate  of  silver  as  long  as  chloride  of  silver  is  thereby 
precipitated.  The  chloride  of  silver  is  removed  by  filtration,  and  the 
fluid  containing  sulphuric  acid  is  distilled,  by  which  the  acid  distils  over 
with  pure  water. 
"When  we  have  determined  by  the  above  described  examination  whether 
the  substance  under  investigation  by  the  action  of  hydrochloric  acid*  is 
decomposed  or  not  into  sugar  and  a  second  product  at  an  elevated  tem- 
perature, we  have  still  to  ascertain  xcliether  by  action  of  an  alhali  in  the 
heat  an  analogous  decomposition  is  effected  or  not.  Many  bodies  afford,  by 
the  treatment  with  baryta,  a  carbohydrate,  and  the  same  decomposition 
product  which  is  obtained  by  treatment  with  hydrochloric  acid.  The 
tannin  of  galls  affords  gallic  acid  as  well  by  the  treatment  with  hydro- 
chloric acid  as  with  baryta  water.  Others  behave  in  this  respect  differ- 
ently, ^sculine  gives,  when  heated  with  hydrochloric  acid,  sesculetine  ; 
on  the  contrary,  by  treatment  with  baryta  water,  no  trace  of  sesculetine  is 
obtained.  With  reference  to  the  carbohydrates,  the  copulated  substances 
behave  likewise  similar  and  dissimilar.    The  tannin  of  galls  treated  with 
*  The  hydrochloric  may  in  these  investigations  be  replaced  by  sulphuric  acid 
with  but  few  exceptions  ;  the  latter  can  be  more  readily  removed  when  the 
decomposition  has  been  completed.  But  in  general  the  decomposition  pro- 
ceeds more  slowly  and  less  completely,  and  often  not  at  all,  with  sulphuric 
acid  than  with  hydrochloric  acid. 
