354 
TECHNICAL  ANALYSIS  OF  SOAP. 
and  mingle  with  them  ;  cool  the  whole,  take  out  the  cake  of  wax, 
and  weigh  it,  previously  drying  it  between  double  filtering 
papers.  The  excess  of  weight  gives  the  proportion  of  fatty 
acids. 
Ash — Soda. — Calcine,  at  red  heat,  5  grms.  of  soap  in  a  pla- 
tinum capsule.  Weigh  the  ash  thus  obtained,  and  dissolve  it  in 
200  c.c.  of  distilled  water;  determine  the  proportion  of  soda  in 
100  c.c.  by  means  of  normal  sulphuric  acid  (alkalimetric  stand- 
ard), evaporate  to  dryness,  and  notice  the  action  of  bichloride 
of  platinum  upon  the  residue  dissolved  in  water,  to  ascertain 
whether  it  consists  of  potash  or  soda.  The  estimation  of  the 
soda  may  be  verified  by  directly  taking  the  alkalimetric  standard 
of  the  soap  (5  grs.). 
Chloride  of  Sodium. — Estimate  the  chlorine  in  50  c.c.  of  the 
solution  with  the  standard  silver  solution. 
Sulphate  of  Soda. — The  sulphuric  acid  is  estimated  in  the  re- 
maining 50  c.c.  of  the  solution  with  chloride  of  barium. 
Nan- Saponified  Fatty  Bodies. — These  also  occur  in  soap,  and 
may  be  detected  as  follows :  Dry  5  grms.  of  soap  at  110°,  after 
which  treat  it  with  common  ether.  Agitate  it  with  that  liquid 
in  a  flask,  filter  it,  wash  with  ether,  and  evaporate  the  solution 
at  100°  ;  the  residue  will  be  the  non-saponified  fatty  bodies. 
The  ether  may,  perhaps,  dissolve  a  little  of  the  soap ;  it  must, 
therefore,  be  ascertained  that  the  residue  is  really  fat — melt  it, 
and  try  whether  it  will  soil  glazed  paper. 
Non- Saponified  Carbonate  of  Soda. — Cut  5  grms.  of  soap 
into  small  fragments,  and  treat  them  with  boiling  alcohol,  which 
does  not  dissolve  carbonate  of  soda.  Filter,  and  treat  the  in- 
soluble residue  with  alcoholic  acetic  acid,  which  dissolves  the 
carbonate  of  soda  without  acting  on  the  sulphate  of  soda  and 
chloride  of  sodium.  The  acetic  solution,  evaporated  to  dryness 
and  calcined,  leaves,  as  a  residue,  carbonate  of  soda.  Weigh  it, 
and,  if  verification  be  required,  take  its  alkalimetric  standard. 
Glycerin. — Dissolve  5  grms.  of  soap  in  boiling  water,  decom- 
pose it  with  dilute  sulphuric  acid,  and  separate  the  isolated  fatty 
acids  by  decantation.  The  liquid,  which  is  completely  neu- 
tralised by  the  carbonate  of  soda,  is  now  evaporated  to  dryness 
