Am.  Jour.  Pharm.  > 
July,  1910.  / 
Analysis  of  Ointments. 
321 
water,  alcohol,  melting,  filtering  and  drying),  the  cholesterin  reac- 
tion can  be  resorted  to.  (See  Hager's  Handb.  der  Pharm.  Praxis, 
vol.  2,  page  276.) 
Glycerin. — It  may  be  detected  by  melting  the  ointment  (see  under 
preliminary  tests)  or  shaking  out  with  hot  water,  evaporating  on  the 
water  bath,  purifying  if  necessary  by  taking  up  residue  with  ether- 
alcohol  (1+3)  and  driving  off  the  solvent.  It  may  be  identified 
by  its  sweet  taste.  On  igniting  with  potassium  bisulphate  the  odor 
of  acrolein  will  be  noticed. 
Denige's  tests  are  also  useful.4  The  glycerin  is  oxidized  to 
dioxyacetone  by  boiling  with  bromine  water  on  the  water  bath,  the 
product  so  obtained  gives  beautiful  color  reactions  with  thymol, 
resorcin,  codein  and  ^-naphthol  in  the  presence  of  concentrated 
sulphuric  acid.  The  reaction  takes  place  either  at  room  temperature 
or  on  heating.  Thymol  produces  a  bordeaux  red  color  changing 
to  pink  red,  on  diluting.  Resorcin  causes  a  blood  red  color  changing 
to  yellowish  red  or  yellow  on  diluting  with  glacial  acetic  acid  or 
sulphuric  acid  (spec.  grav.  1.8).  Codein  gives  a  greenish  blue  and 
/?-naphthol  an  emerald  green  color  with  green  fluorescence.  If  a 
solution  of  salicylic  acid  and  potassium  bromide  is  heated  with 
dioxyacetone  for  two  minutes  on  the  water  bath,  a  violet  color  is 
obtained ;  the  salicylic  acid  may  be  substituted  by  guaiacol,  the  color 
produced  will  be  a  deep  blue.  Dioxyacetone  gives  the  hydrazine 
reaction  with  phenylhydrazine,  acetic  acid  and  sodium  acetate,  the 
crystals  can  be  identified  under  the  microscope.  Equal  volumes  of 
dioxyacetone  solution  and  Nessler's  reagent  or  Fehling's  solution 
produce  on  heating  a  precipitate  of  metallic  mercury  and  cuprous 
oxide,  respectively. 
Casein. — Frequently  used  in  skin  creams,  is  insoluble  in  water, 
alcohol  and  ether.  It  is  soluble  in  dilute  caustic  alkali  or  alkaline 
carbonates  also  in  diluted  hydrochloric  acid,  containing  less  than 
0.1  per  cent,  of  hydrochloric  acid.5  Casein  consists  of  about  14  per 
cent,  nitrogen. 
Borax  and  Boric  Acid. — About  five  grammes  of  the  ointment  are 
melted  in  a  flask  and  shaken  with  10  to  15  c.c.  warm  water,  acidu- 
lated with  hydrochloric  acid.  The  liquid  is  filtered  off  from  fat  or 
insoluble  material  when  cold  and  tested  with  turmeric  paper  and 
ammonia.  A  negative  reaction  shows  the  absence  of  either  borax 
or  boric  acid  which,  when  added  to  an  ointment,  are  present  in 
nearly  all  cases  in  a  quantity  of  not  less  than  0.5  per  cent.  Boric 
