rochleder's  proximate  analysis. 
181 
bases  contained  in  the  distillate,  a  cohobation  would  be  superfluous  even 
when  their  quantity  was  very  small. 
The  treatment  of  the  watery  decoction  and  the  watery  distillate  for  the 
purpose  of  ascertaining  their  constituents,  the  next  section  will  describe. 
II. —  Treatment  of  the  material  to  be  examined  with  cold  vjater. 
A  portion  of  the  material,  as  finely  divided  as  possible,  is  treated  with 
cold  water.  As  much  water  is  employed  as  will  thorughly  saturate  the 
material,  and  cover  it  about  a  couple  of  lines.  After  a  short  time,  the 
saturated  mass  is  placed  upon  a  fine  strong  piece  of  linen,  and  the  liquid 
pressed  off  by  a  gradually  increased  force.  The  liquid  thereby  obtained  is 
filtered  through  moist  paper,  in  as  many  small  filters  as  possible.  In 
most  cases  the  liquid  passes  slowly  through  the  filters.  By  this  method 
of  treatment  it  is  not  possible  to  prevent  the  formation  of  decomposition 
products  by  the  action  of  the  ferment  on  the  other  constituents.  As  all 
these  decompositions  proceed  with  more  difficulty  in  proportion  to  the 
lowness  of  the  temperature,  this  disadvantage  may  be  considerably  removed 
by  employing  ice-cold  water  for  the  extraction,  and  by  preventing  the 
heating  of  the  filtering  liquid  by  surrounding  the  funnels  with  such  water. 
The  filtrates  should  be  collected  in  vessels  surrounded  with  cold  water. 
The  further  investigation  of  this  filtered  liquid  will  be  described  in  the 
next  section.  It  serves  principally  for  the  detection  of  those  substances 
which  remain  undissolved  by  the  treatment  of  the  material  with  boiling 
water,  because  they  become  by  elevated  temperatures  insoluble  in  water, 
that  is  coagulated,  as  is  the  case  with  bodies  analogous  to  albumen, 
emulsin,  &c. 
III.  — Treatment  of  the  substance  to  be  examined  with  acidulated  water. 
A  portion  of  the  material  is  treated  with  water,  to  which  a  little  sul- 
phuric acid  has  been  added,  and  heated  in  a  water-bath,  or  by  a  current 
of  steam.  The  boiling  hot  fluid,  together  with  the  material  previously 
placed  therein,  is  allowed  to  cool,  and  the  fluid  is  separated  from  the  un- 
dissolved material,  which  is  then  gently  expressed.  This  fluid  serves 
chiefly  to  detect  some  few  organic  acids  which  are  contained  in  the  mate- 
rial, in  the  form  of  salts  insoluble  in  water  and  alcohol,  but  which  are  set 
free  by  the  sulphuric  acid,  and  thereby  become  soluble  in  water  ;  and  also 
to  show  the  presence  of  organic  bases,  which  are  contained  in  the  form  of 
sulphates  in  this  extract. 
IV.  —  Treatment  of  the  material  to  he  examined  with  ammonical  water. 
For  the  preparation  of  the  extract  with  water  to  which  a  little  caustic 
ammonia  has  been  added,  a  small  quantity  of  the  residue  is  taken  which  is 
obtained  after  boiling  the  material  with  water  and  expressing  it.  This 
residue  is  introduced  into  water  containing  ammonia,  and  the  whole 
allowed  to  stand  quietly  some  time,  until  the  liquid  has  properly  saturated 
the  substance.    After  passing  the  liquid  through  linen  and  expressing 
