472 
rochleder's  proximate  analysis. 
phuric  acid.  As  chloride  of  barium  is  almost  insoluble  in  quite  anhydrous 
alcohol,  and  the  majority  of  the  baryta  compounds  of  organic  substances, 
on  the  contrary,  dissolve  with  great  difficulty  in  weak  spirit,  we  can,  when 
baryta  water  produces  no  precipitate  in  the  hydrochloric  acid  fluid,  add 
absolute  alcohol,  whereby  a  baryta  compound  of  the  decomposition  product 
is  often  thrown  down  before  the  chloride  of  barium  separates. 
It  is  self  evident  that  the  fluid  containing  hydrochloric  acid,  which  is 
obtained  by  heating  the  aqueous  solution  of  the  crystals  under  examina- 
tion with  a  little  hydrochloric  acid,  may  be  mixed  with  baryta  water,  to 
observe  whether  a  precipitate,  that  is,  a  compound  of  the  decomposition 
product,  insoluble  in  water,  is  thereby  formed  or  not ;  in  the  latter  case, 
the  addition  of  a  little  anhydrous  alcohol  assists  the  precipitation.  If  a 
precipitate  is  not  produced  either  by  baryta  water  alone,  or  by  baryta 
water  and  alcohol,  a  second  portion  of  the  fluid,  containing  hydro- 
chloric acid,  is  taken  and  mixed  with  freshly  precipitated  carbo- 
nate of  silver,  which  is  converted  into  insoluble  chloride  of  silver 
by  the  hydrochloric  acid,  under  the  evolution  of  carbonic  acid.  The 
chloride  of  silver  is  separated  by  filtration  from  the  fluid,  which  is  now 
free  from  hydrochloric  acid.  Two  cases  can  hereby  happen.  Either  there 
results,  besides  the  chioride  of  silver,  the  silver  compound  of  a  decomposi- 
tion product  insoluble  in  water  or  not.  If  no  insoluble  compound  of  a  decom- 
position product  with  silver,  has  soparated  with  the  chloride  of  silver,  the 
filtered  fluid  contains  silver  or  not.  If  it  contains  silver,  the  silver  must  be 
separated  by  sulphuretted  hydrogen  ;  then  we  have  a  watery  solution  of  both 
decomposition  products.  If  it  does  not  contain  silver,  the  filtrate  is  a  pure 
solution  of  decomposition  products.  Of  their  further  treatment  we  shall  di- 
rectly speak.  When  a  decomposition  product  is  precipitated,  together  with 
chloride  of  silver,  as  an  insoluble  silver  compound,  and  filtered  off,  the  filtered 
fluid  is  a  solution  of  sugar,  or  a  solution  of  a  cr.rbohydrate  with  Ihe  same 
composition  as  sugar.  When  the  solution  of  both  decomposition  products  is 
obtained  in  a  condition  free  from  hydrochloric  acid,  we  must  endeavor  to 
effect  a  separation  with  bichloride  of  tin,  or  with  basic  acetate  of  lead.  Many 
of  the  decomposition  products  appearing  with  sugar  are  precipitated  by 
bichloride  of  tin,  and  most  of  these  bodies  are  thrown  down  by  basic  acetate 
of  lead.  The  tin  and  lead  compounds  obtained  may  be  decomposed  by  sul- 
phuretted hydrogen,  after  they  have  been  diffused  in  water.  The  fluid 
filtered  from  these  tin  and  lead  compounds,  after  treatment  with  sul- 
phuretted hydrogen,  can  be  employed  for  obtaining  the  sugar. 
If  the  research  which  has  been  made  with  both  portions  of  the  fluid 
under  examination  has  lead  to  no  result,  a  third  portion  of  the  fluid,  con- 
taining hydrochloric  acid,  is  taken  and  mixed  with  a  solution  o{  sulphate  of 
silver  as  long  as  a  turbidness  arises  from  precipitated  chloride  of  silver.  The 
chloride  of  silver  is  removed  by  filtration,  the  fluid  containing  sulphuric 
acid  is  mixed  with  baryta  water  as  long  as  sulphate  of  baryta  separates, 
and  by  filtration  a  solution  of  both  decomposition  products  is  obtained  free 
from  acid. 
