Am.  Jour.  Pharm. 
Sept.  1875. 
Analysis  of  Graphite. 
395 
process  the  clay  is  entirely,  partially,  or  not  at  all  lost  in  the  alkaline 
iye,  is  a  question  of  little  importance,  because  it  will  undoubtedly  be 
dissolved  by  the  following  action  of  HCl  ;  the  silica,  on  the  contrary, 
should  be  entirely  dissolved  ;  although,  taking  in  consideration  the  applied 
treatment,  that  result  could  be  expected,  still  I  was  not  quite  success- 
ful. A  re-fusion  of  the  residue  would  probably  have  extracted  the 
small  amount  of  silica  remaining,  but  further  investigations  led  to  the 
conclusion  that  it  was  not  needed. 
That  the  graphite  would  not  stand  the  melting  without  some  loss 
was  foreseen,  and  proved  itself  by  the  continual  bubbling  of  the  mass  ; 
the  loss  of  carbon  thereby  experienced  was  of  not  much  consequence 
to  the  result  of  the  analysis,  as  all  the  other  constituents  can  readily  be 
determined  by  weight ;  the  final  loss  is  considered  carbon,  and  added 
to  the  previously  obtained  carbon. 
After  the  residue  in  the  filter  has  been  well  washed  with  water  it  is 
dried  and  introduced  into  a  small  flask,  the  ashes  of  the  filter,  to  which 
traces  of  the  substance  adhere,  and  about  3  grams  of  HCl,  of  specific 
gravity  i*i2,  being  added.  After  a  few  minutes  a  feeble  gelatinizing 
of  the  liquid  is  perceptible,  caused  by  the  decomposition  of  the  little 
alkali-silicate  which  was  not  removed  by  the  lixiviation.  If  a  small 
amount  of  HCl  be  added,  the  precipitate  disappears  again,  leaving  the 
silica  in  solution.  After  digesting  for  about  an  hour,  dilute  with  water, 
filter  and  wash  ;  the  substance  remaining  on  the  filter  is  pure  graphite- 
carbon,  which,  after  being  dried  and  heated  to  a  dull  incandescence,  is 
weighed. 
Unite  the  acid  filtrate  with  the  previously  obtained  alkaline  filtrate  \ 
add  a  sufficient  quantity  of  HCl  to  impart  an  acid  reaction  ;  evaporate 
to  dryness  and  determine  the  silica,  clay,  FeO,  etc.,  in  the  usual  man- 
ner. After  treating  two  samples  of  graphite  by  the  above-described 
method,  they  showed  the  following  composition  : 
I. 
IL 
Carbon, 
.  58-04 
68-20 
Silica,         .           .           .  . 
13-10 
5'33 
Clay,    .           .           „  . 
io'7o 
6-n 
Oxide  of  Iron, 
2'74 
2-20 
Lime,  .... 
0*05 
0-03 
Magnesia,  .           .           .  . 
trace 
trace 
Loss  (Carbon)  .  . 
•  13*55 
12-53 
Water,       .           .           .  . 
1-82 
5-60 
lOOOO 
I00"00 
