376 
rochleder's  proximate  analysis. 
avoidable.  Besides,  that  which  has  been  indicated  above  concerning  the 
individual  reagents,  clearly  shows  in  what  manner  and  to  what  purpose 
each  reagent  shall  be  used,  where  in  previous  paragraphs  it  has  been  only 
briefly  pointed  out  that  reagents  should  be  used  for  the  further  investiga- 
tion. Assuming  that  by  treatment  of  the  precipitate  with  acetic  acid, 
which  sugar  of  lead  produced  in  the  watery  decoction  of  the  material  under 
examination,  we  have  the  precipitate  separated  into  a  part  soluble  and  a 
part  insoluble  in  acetic  acid,  the  part  soluble  in  acetic  acid  precipitated  by 
subacetate  of  lead  into  two  portions,  because  by  subacetate  of  lead  a  pre- 
cipitate results  when  the  fluid  still  reacts  acid,  while  a  second  precipitate 
makes  its  appearance  when  the  acid  fluid  is  neutralized  by  the  addition  of 
subacetate  of  lead :  assuming  that  by  treatment  of  both  lead  salts  with 
alcohol,  we  have  separated  them  into  a  part  soluble  and  a  part  insoluble 
in  alcohol,  and  thus  obtained  four  portions  of  lead  salts  of  the  precipitate 
from  the  part  soluble  in  acetic  acid  produced  by  sugar  of  lead  in  the  watery 
decoction  of  the  material  under  examination  ;  assuming  that  we  have  de- 
composed the  part  of  this  precipitate  insoluble  in  acetic  acid  under  water  by 
sulphuretted  hydrogen,  the  fluid  filtered  from  the  sulphuret  of  lead,  freed 
from  the  excess  of  sulphuretted  hydrogen,  and  thrown  down  ten  lead  salts 
by  fractional  precipitation  with  sugar  of  lead,  we  have  prepared  in  this 
way  fourteen  lead  salts  from  the  single  precipitate  thrown  down  by  sugar 
of  lead  in  the  watery  decoction  of  the  material  under  examination.  By 
the  decomposition  of  these  lead  salts  with  sulphuretted  hydrogen,  we  have 
fourteen  aqueous  solutions,  which  are  now  to  be  tested  with  reagents.  It  is 
self-evident  that  certain  reagents  are  not  here  required  to  be  employed,  be 
cause  no  representative  can  be  contained  in  these  fluids  of  the  class  of  bodies 
for  which  they  could  be  used  with  results.  We  have  found  in  the  precipitate 
produced  by  sugar  of  lead  partly  inorganic  and  partly  organic  acids  combined 
with  lead,  no  indifferent  carbohydrates  and  no  bases,  because  their  precipita- 
tion is  prevented  by  the  acetic  acid  rendered  free.  The  vegetable  acids  ex- 
isting generally  as  malic  acid,  citric  acid,  tartaric  acid,  fumaric  or  aconitic 
acid,  the  tannic  acids,  the  acids  corresponding  to  gallic  acid,  substances 
which  are  so  widely  spread  in  the  vegetable  kingdom,  are  contained  in  this 
precipitate,  by  the  investigation  of  the  bark,  the  leaves,  the  stems,  and  the 
flowers  of  plants.  Coloring  matters,  often  formed  by  the  oxidation  of  the 
various  forms  of  tannin  or  their  splitting  up,  are  produced  from  colorless 
bodies.  Gelatinous  bodies  of  the  class  of  pectine  compounds  are  frequently 
present  in  this  precipitate.  Coloring  matters  and  pectine  bodies,  by  the 
decomposition  of  the  lead  compound  with  sulphuretted  hydrogen,  are  often 
entirely  retained  in  the  sulphuret  of  lead,  partly  because  sulphuret  of  lead 
acts  analogous  to  animal  charcoal,  and  partly  because  they  were  present 
in  the  watery  decoction  in  the  form  of  soluble  salts.  By  precipitation  with 
sugar  of  lead  the  base  of  the  soluble  salt  is  separated  as  an  acetate,  the 
acid  precipitated  with  the  oxide  of  lead,  and  retained  by  the  sulphuret  of 
(To  be  continued.) 
