212  Proximate  Analysis  of  Plants.       {  ^"•a&So!'"" 
balance,  sensitive  to  at  least  '5  milligram,  and  the  ordinary  glass  and  porcelain- 
ware  found  in  all  laboratories. 
It  is  assumed  that  whoever  attempts  the  analysis  oF  a  plant  is  informed  as  to  the 
normal  constituents  to  be  sought,  that  he  has  had  considerable  experience  in  inor- 
ganic analysis,  and  in  the  identification  of  the  principal  classes  of  proximate  con- 
stituents, which  he  now  undertakes  to  estimate  quantitatively.  Accordingly,  tests 
for  identification  will  not  be  here  presented  ^  they  should,  however,  never  be  omitted. 
The  necessity  of  recording  in  detail  all  physical  and  chemical  peculiarities  with 
every  weight  that  is  taken  is  self-evident. 
A  Method  for  the  Proximate  Analysis  of  Plants. 
I.  Preparation  of  Sample. 
The  air-dry  specimen  should  be  carefully  examined,  and  all  extraneous  substances 
removed.  The  entire  sample  should  then  be  ground,  or  beaten  in  an  iron  mortar,, 
until  it  will  all  pass  through  a  sieve  having  from  40  to  60  meshes  to  the  linear  inch. 
After  thoroughly  mixing  this  sample,  take  of  it  about  100  grams,  which  should  be- 
further  pulverized  until  it  will  all  pass  through  a  sieve  having  from  80  to  100  meshe& 
to  the  linear  inch.  From  this  smaller  portion  remove  all  iron,  derived  from  mill  or 
mortar,  by  use  of  a  magnet.  Then  place  in  a  clean,  dry  bottle,  which  should  be 
labeled  and  securely  corked.  This  small  sample  is  for  the  analysis}  the  larger 
portion  should  be  reserved  for  the  separation  of  those  proximate  principles  which 
seem,  from  the  analysis,  to  be  worthy  of  more  extended  investigation. 
II.  Estimation  of  Moisture. 
Dry  rapidly,  at  100  to  izo^C,  two  or  more  grams  of  the  sample  ;  the  loss  of  weight 
equals  moisture  and  occasionally  a  little  volatile  oil.  In  some  cases  it  is  best  to  dry 
at  a  lower  temperature,  and  at  other  titnes  the  drying  should  be  conducted  in  a. 
stream  of  hydrogen  or  carbonic  anhydride. 
Ill     Estimation  of  Ash. 
In  a  weighed  crucible  gently  ignite  two  or  more  grams  of  the  sample  until  nearly 
or  quite  free  from  carbonaceous  matter  5  the  heat  should  not  be  permitted  to  rise- 
above  faint  redness,  or  loss  of  alkaline  chlorides  may  occur.  Weigh  this  residue  as 
crude  ash,  and  in  it  determine: 
a.  Amount  Soluble  in  Water, — This  portion  may  contain  chlorides,  sulphates,, 
phosphates  and  carbonates  of  potassium  and  sodium;  also  slight  amounts  of  chlor- 
ides and  sulphates  of  calcium  and  magnesium. 
b.  Insoluble  in  Water:,  Soluble  in  Dilute  Hydrochloric  Acid. — The  residue  from  a 
should  be  treated  with  a  slight  excess  of  hydrochloric  acid,  and  evaporated  in  a 
porcelain  dish  over  a  water  bath  until  all  free  acid  has  been  expelled  ;  it  should  then 
be  again  moistened  with  hydrochloric  acid,  water  added,  and  be  filtered  from  any- 
remaining  insoluble  substances.  This  treatment  removes  carbonates  (with  decom- 
position) and  phosphates  of  calcium  and  magnesium,  sulphate  of  calcium  and  oxides 
of  iron  and  manganese, 
c.  Insoluble  in  Water  ,•  Insoluble  in  Dilute  Hydrochloric  Acid  j  Soluble  in  concentrated' 
Sodic  Hydrate. — Boil  the  residue  from  b  with  a  solution  containing  about  twenty  per 
cent,  of  sodic  hydrate.  This  treatment  removes  combined  silica  of  the  ash.  The 
residue  still  insoluble  is  sand  and  clay  which  adhered  to  the  specimen;  this  residue 
should  be  separated,  washed  thoroughly,  and  weighed. 
