354 
Analysis  of  Soap. 
/  Am.  Jour.  Pharm. 
t     Aug.  1,1874. 
with  hot  water  on  filter  and  test  solution  volumetrically  by  a  gradu- 
ated normal  solution  of  oxalic  acid.  Every  c.  c.  used  will  indicate 
•053  grams  of  Na2C03.  Incidentally  notice  whether  any  precipitate 
of  calcic  oxalate  occurs.  Subtract  the  weight  of  sodic  carbonate 
from  the  whole  weight  of  residue  insoluble  in  alcohol,  and  the  remain- 
der is  the  weight  of  salts  and  foreign  matter.  This  can  be  further 
analyzed,  if  it  is  desired. 
(2).  Filtrate.    (Alcoholic  solution  of  soap  and  free  alkali). 
Pass  through  it  a  stream  of  carbonic  acid  gas,  if  precipitate  forms 
continue,  until  precipitation  ceases ;  filter ;  dissolve  precipitate  in 
water,  and  estimate  with  normal  graduated  solution  of  oxalic  acid,  as 
before.  Every  c.  c.  indicates  -031  grams  of  free  soda,  or  *047  of  free 
potash,  as  the  case  may  be.  No  precipitate  indicates  absence  of  free 
alkali. 
The  filtrate  from  the  precipitate  by  carbonic  acid,  or,  if  no  precipi- 
tate has  occurred,  then  the  alcoholic  solution,  after  the  addition  of 
about  one  ounce  of  water,  is  evaporated  on  a  water-bath  until  all  the 
alcohol  has  escaped  (a  retort  may  be  used,  if  it  is  desirable,  to  save 
the  alcohol).  To  the  aqueous  solution  is  then  added  normal  gradu- 
ated solution  of  oxalic  acid,  until  it  is  acid  to  litmus  paper.  Each 
c.  c.  required  indicates  *031  grams  combined  soda,  or  "047  grams  of 
combined  potash. 
A' little  sulphuric  acid  is  now  added,  to  separate  the  fatty  acids- 
more  rapidly.  Ten  grams  of  beeswax — previously  melted  to  free  it 
from  water — is  added,  and  the  whole  placed  on  a  water-bath  until  the 
fatty  acids  have  mixed,  forming  a  stratum  on  the  top  of  the  liquid. 
The  mixture  is  then  set  aside  to  cool,  and  the  cake,  or  solidified  stra- 
tum, removed,  dried  and  weighed.  Subtract  weight  of  beeswax,  and 
the  remainder  is  the  weight  of  fatty  acids  and  resin. 
c.  (1.)  Take  forty  grams,  dissolve  in  water,  add  dilute  H2S04  until 
precipitation  ceases,  and  set  aside  in  a  cool  place  (below  57°  F). 
The  fatty  acids  will  rise  to  the  top,  when  they  may  be  dried  and 
weighed. 
(2.)  Digest,  with  constant  mixing,  the  fatty  acids  with  a  mixture 
of  water,  with  nearly  as  much  alcohol,  until  the  subsident  liquid  (when 
the  mixture  has  cooled  and  the  fatty  acids  again  solidified)  ceases  to 
be  milky.    Weigh  fatty  stratum  again,  and  subtract  from  weight  ob- 
