320 
Analysis  of  Ointments. 
/Am.  Jour.  Pharm. 
\       July,  1910. 
follows :  On  slightly  heating  in  a  test  tube  one  to  two  c.c.  neutral 
methyl  sulphate  with  a  little  colophony,  a  rose  red  color 
is  obtained  which  changes  to  violet  and  disappears  on  further 
heating.  Neutral  ethyl  sulphate  may  be  used  for  methyl  sulphate. 
Resin,  having  a  melting  point  of  900  to  1300  C,  will  increase  the 
melting  point  when  added  to  fats  as  in  cerates.  A  very  character- 
istic odor  can  be  observed  on  blowing  out  the  flame  of  a  burning 
ointment  containing  an  appreciable  amount  of  resin. 
Detection  of  Certain  Fats  and  Rosin  by  the  Odor  of  Their 
Acids. — About  three  grammes  of  the  ointment  are  saponified  with 
alcoholic  potash  solution  and  the  alcohol  evaporated  on  the  water 
bath.  The  resulting  soap  is  taken  up  with  water  and  the  aqueous 
solution  acidulated  with  hydrochloric  acid.  Tallow  gives  the  odor 
of  mutton  broth ;  colophony  and  various  other  fats  and  resins  also 
yield  characteristic  odors. 
Beeswax. — Should  the  odor  fail  to  give  a  clue,  the  admixture  of 
beeswax  to  an  ointment  may  be  suspected  from  the  peculiar  clouds 
formed  in  a  solution  in  petroleum  ether.  Beeswax  is  only  partially 
soluble  in  petroleum  ether,  whereas  most  of  the  fats,  oils,  paraffin, 
etc.,  are  readily  soluble  in  this  solvent.  It  is  important  that  water, 
volatile  substances  as  carbolic  acid,  mineral  constituents  have  been 
removed  before  applying  this  test.  Resin,  castor  oil  and  other 
alcohol  soluble  substances  must  be  removed  by  shaking  the  sample 
two  to  three  times  with  hot  alcohol,  filtering  off  and  drying  the 
remaining  excipient.  If  about  0.3  grammes  of  the  so  prepared 
ointment  base  are  dissolved  in  4  c.c.  petroleum  ether  in  a  tes1. 
tube  at  a  temperature  of  about  180  C.  it  will  be  found  in  the  presence 
of  beeswax  that  clouds,  consisting  of  very  small  needles,  are  sus- 
pended in  the  solvent.  Compare  with  a  solution  of  a  little  wax  in 
petroleum  ether.  To  examine  these  needles  under  the  microscope 
it  is  best  to  mix  a  drop  of  olive  oil  on  a  slide  with  a  little  of  the 
petroleum  ether  containing  the  needles  in  suspension  before  cover- 
ing with  cover  glass.  Unfiltered  wax  shows  pollen  under  the 
microscope. 
Lanolin, — Lanolin  is  only  very  slightly  saponified  by  an  aqueous 
solution  of  potassium  hydroxide ;  it  can  be  saponified,  however,  with 
an  alcoholic  solution  of  potassium  hydroxide,  though  with  difficulty, 
preferably  under  pressure.  For  its  detection,  provided  it  can  be 
separated  sufficiently  from  other  admixtures  (either  by  shaking  out 
with  chloroform  or  removing  foreign  substances  by  shaking  with 
