Am.  Jour.  Pharm. ) 
April,  1880.  j 
Proximate  Analysis  of  Plants, 
n  I 
most  excellent  examples  of  accurate  examinations  of  vegetable  substances^  as 
instances  may  be  cited,  the  examination  of  ginger,  by  J.  C.  Thresh,^  and  of  ergot,- 
aloes,^  and  other  articles  by  Prof.  DragendorfF  To  these  sources  the  student  must 
look  for  his  best  models  until  a  more  thorough  and  systematic  training  is  given 
American  students  in  proximate  organic  analysis. 
In  following  the  plan  now  presented,  the  use  of  the  apparatus  for  repercolation  is 
strongly  urged  for  the  extractions  with  benzol,  alcohol  and  other  volatile  solvents. 
A  very  simple  and  inexpensive  apparatus  has  been  described  by  various  American 
and  foreign  chemists.^ 
"In  any  convenient  water-tight  vessel  is  a  worm  of  block-tin  pipe,  having  an 
internal  diameter  of  9  mm.,  and  a  length  of  about  2*5  meters.  The  lower  (external) 
part  of  this  worm  is  fitted  by  an  ether  soaked  velvet  cork  to  a  glass  percolator, 
having  a  diameter  of  4  cm.,  a  length  of  20  cm.  to  the  constriction,  and  5  cm.  below. 
Within  this  percolator  is  a  smaller  tube,  flanged  at  the  top  and  bottom,  and  sus- 
pended by  fine  platinum  or  copper  wires.  This  tube  has  a  diameter  of  2*5  to  2'8 
cm.,  and  a  length  of  14  cm. 5  the  bottom  is  covered  by  filter  paper  and  fine  washed 
linen,^  tied  on  by  linen  thread.  The  weighed  sample  of  the  finely  powdered  herb 
is  placed  within  this  tube  for  extraction.  A  light  glass  flask,  weighing  about  30 
grams,  is  fitted  by  an  ether-soaked  cork  to  the  outer  percolator.""  Having  intro- 
duced the  solvent  into  this  glass  flask  the  connections  are  made  secure,  and  heat  is 
applied  by  a  water-bath  to  the  flask.  If  the  liquid  is  too  slowly  volatilized  the 
addition  of  a  little  common  salt  to  the  water  in  the  bath  serves  to  remove  the  trouble. 
Next  in  importance  is  the  use  of  a  good  tared  filter.  The  form  originally  pre- 
sented by  F  A.  Gooch*'  leaves  little  to  be  desired.  It  may  be  made  by  perforating 
with  fine  holes  the  bottom  of  an  ordinary  platinum  crucible,  and  fitting  it  accu- 
rately to  a  perforation  made  in  a  large  rubber  cork;  this  cork  connects  It  with  a 
receiving  vessel,  which  in  turn  is  connected  with  a  Bunsen's  pump.  Fine  asbestus 
suspended  in  water  is  poured  into  the  crucible,  the  air  exhausted  from  the  receiving 
vessel,  and  thus  a  firm,  thin  layer  of  asbestus  is  deposited  on  the  bottom  of  the  cru- 
cible. After  ignition  and  weighing  the  crucible  is  ready  for  the  reception  of  any 
precipitate  which  it  is  desired  to  separate  and  weigh. 
The  use  of  these  two  pieces  of  apparatus  will  eliminate  two  grave  sources  of  error, 
viz.,  incomplete  extraction  of  soluble  matters,  and  inaccuracies  introduced  by  the 
use. of  tared  paper  filters. 
The  other  necessary  apparatus  is  simple,  and  includes  one  or  more  platinum  cru- 
cibles and  evaporating  dishes,  accurate  burettes  and  graduated  cylinders,  a  good 
1  "Phar.  Jour.  Trans."  [3],  10,  81,  Aug.,  1879.    "Am.  Jour.  Phar.,"  1879,  p.  519. 
2  "  Phar.  Jour.  Trans."  [3],  6,  looi,  June  17,  1876.    "Am.  Jour.  Phar.,"  1876,  p.  413 ;  1878,  p.  335. 
3  "Werthbestimmung,"  1874,  p.  no. 
4B.  Tollens,  "  Zeitsch.  f.  Anal.  Chem."  [17],  320,  1878;  "New  Remedies"  [7],  335,  Nov.,  1878;  W. 
O.  AttVater,  Proc.  Am.  Chem.  Soc."  [2[,  2,  p.  85  ;  S.  W.  Johnson,  "Am.  Jour.  Sci.  Arts  "  [13],  196  ; 
H.  B  Parsons,  "New  Remedies"  [8],  293,  Oct.,  1879. 
5  In  place  of  the  linen  and  filter  paper  may  be  substituted  fine  brass  or  platinum  wire  gauze.  Asbestus 
suspended  in  water  may  then  be  poured  in  to  form  a  fine  felt.  The  tube;Can  then  be  dried  and  weighed, 
and  the  amounts  extracted  may  be  found  by  the  loss  of  weight  of  the  tube  and  substance.  A  little 
■experimentation  will  show  the  operator  how  to  prepare  and  use  the  tube.  It  is  but  an  adaptation  of  the 
Gooch's  Filter  here  recommended. 
«"Proc.  Amer.  Acad.  Sci."  [13],  p.  342,  1878;  "New  Remedies"  [7],  p.  200,  Oct.,  1878;  "Am 
Chem.  Journ.,"  p.  i,  317. 
