rochleder's  proximate  analysis. 
85 
Probably  these  might  be  partially  separated  by  the  employment  of  sul- 
phuret  of  carbon,  and  thus  the  analysis  facilitated.     Unfortunately,  at 
present  such  a  few  data  lie  before  us  upon  the  applicability  of  this  fluid, 
which  was  first  employed  by  Lampadius  for  separations  of  that  kind,  that 
I  am  not  in  a  position  to  give  more  information  with  regard  to  the  employ- 
ment of  this  body  in  the  treatment  of  the  mixtures  in  question.  So 
much  is  certain,  that  the  analysis  of  these  mixtures  belongs  often  to 
the  most  difficult  problems.     As  all  fats,  as  well  as  kinds  of  wax, 
dissolve  at  least  in  hot  ether,  but  only  some  of  the  resins,  it  is  convenient 
to  effect  a  separation  by  ether  into  a  soluble  part,  and  a  part  insoluble 
therein,  and  to  examine  both  after  distilling  off  the  ether  more  closely, 
supposing  that  the  whole  mass  is  not  soluble  in  ether,  which  often  happens. 
Some  bodies  in  such  mixtures  are  soluble  in  hot  or  boiling  alcohol,  and 
sparingly  soluble  in  cold  alcohol,  as,  for  example,  some  kinds  of  wax.  A 
partial,  though  not  an  exact  separation,  can  be  effected  by  dissolving  the 
mixture  in  the  smallest  possible  quantity  of  boiling  alcohol,  and  then  cool- 
ing the  solution.    I  shall  come  directly  to  another  method  for  the  separa- 
tion of  this  mixture  into  its  constituents.     But  I  must  here  remark  that 
fats,  when  present  in  great  quantity,  as,  for  example,  in  the  seeds  poor  in 
starch  or  in  some  roots,  are  seldom  accompanied  by  resins  in  considerable 
quantity,  and  viee  versa,  leaves,  woods,  flowers,  &c,  rich  in  resin,  contain 
seldom  more  than  a  trace  of  fat,  so  that  we  have  to  do  either  with  a  pre- 
ponderance of  fats,  or  a  preponderance  of  resins,  at  least  in  the  majority  of 
cases.    On  the  contrary,  with  resins,  waxy  substances  frequently  exist  to- 
gether.   It  has  been  already  stated  that  vegetable  bodies  rich  in  fat  are 
freed  generally  by  pressure  from  the  bulk  of  the  fat,  and  the  quantity  of  fat 
necessary  for  its  investigation  can  be  obtained  almost  in  a  pure  condition. 
And  it  has  likewise  been  mentioned  before  that  the  expressed  residues,  as 
well  as  such  material  which  cannot  be  freed  from  its  fat  by  pressure,  are  to 
be  exhausted  with  a  weaker  alcohol  in  order  to  obtain  alcoholic  tincture 
as  free  from  fixed  oil  as  possible. 
I  have  therefore  to  give  the  method  by  which  a  mixture  of  resins  con- 
taining waxy  bodies  and  a  mixture  of  fats  are  to  be  treated,  to  ascertain 
the  individual  constituents  of  these  mixtures.  The  mixture  of  resins ,  which 
contains  admixed  waxy  bodies,  must,  before  it  is  submitted  to  investiga- 
tion, be  subjected  to  some  preliminary  experiments,  which  are  performed 
with  small  quantities  of  it.  A  small  portion  of  the  resinous  mixture  is 
treated  in  a  mortar  with  water  to  which  a  little  ammonia  ha6  been  added, 
and  the  resinous  mass  is  kneaded  with  the  pestle  into  the  closest  possible 
contact  with  the  alkaline  fluid.  Many  resins  possess  the  character  of  weak 
acids.  These  resins  dissolve  in  the  ammoniacal  water,  while  the  indifferent 
resins  remain  undissolved  by  this  treatment.  By  filtration  the  undissolved 
substances  are  separated  from  the  solution,  and  from  this  the  dissolved 
resins  are  thrown  down  by  dilute  hydrochloric  acid.    By  these  means  the 
