ON  TESTS  FOR  THE  PURITY  OF  GLYCERIN. 
117 
ON  TESTS  FOR  THE  PURITY  OF  GLYCERIN. 
By  J.  M.  Maisch. 
The  application  of  Trommer's  test  for  the  detection  of  glucose 
and  allied  carbohydrates  is  so  frequently  made,  that  every 
pharmaceutist  might  be  supposed  to  be  familiar  with  it ;  it  con- 
sists simply  in  adding  to  the  liquid  to  be  tested  a  little  solution 
of  sulphate  of  copper  and  then  caustic  potassa  or  soda,  until  the 
precipitate  at  first  appearing  is  redissolved ;  the  mixture  is  grad- 
ually heated  to  the  boiling  point,  when  it  becomes  turbid  and 
changes  its  color  to  yellow  and  red,  if  grape  sugar,  &c,  is  pre- 
sent. This  reduction  to  suboxide  of  copper  does  not  take  place 
at  the  ordinary  temperature. 
The  "  Druggists'  Circular,"  for  January,  contained  a  commu- 
nication on  "  sugar  in  glycerin,"  sulphate  of  copper  and  potassa 
being  used  as  the  test.  Yet,  though  boiling  was  resorted  to  only 
in  one  instance,  resulting  in  a  failure  to  get  the  precipitated  sub- 
oxide of  copper,  it  was  endorsed  as  "Trommer's  test,"  and  as 
evidence  of  the  presence  of  glucose.  To  any  one  conversant  with 
the  manipulation,  the  "  pale  tint,"  "  intense  blue  color"  and 
"particles  like  flock  of  wool,"  spoken  of  in  the  communication, 
will  readily  explain  themselves.  » 
The  February  number  of  the  "Druggists'  Circular"  states  that 
the  inferences  of  that  communication  were  incorrect,  so  far  as 
Bower's  Glycerin  is  concerned,  while  it  is  evident  that  all  infer- 
ences are  incorrect.  But  Dr.  Newton  further  states  that  "  the 
tests  usually  applied  will  lead  to  a  false  estimate  of  its  (Bower's 
or  all  glycerin  ? )  quality  ;"  the  tests,  however,  are  n  t  named. 
This  statement,  if  correct,  would  upset  all  the  researches  made 
thus  far  on  testing  for  the  purity  of  glycerin.  To  ascertain  the 
correctness  of  this  assertion,  four  samples  of  glycerin  were  ex- 
amined, namely:  1,  "Vienna"  glycerin,  bearing  the  label  of 
F.  A.  Sarg ;  2,  Bower's  glycerin,  recently  obtained ;  3,  the 
same,  which  had  been  on  hand  about  two  and  a  half  years ; 
4,  glycerin  manufactured  in  the  West.  The  last  was  at  least 
thirty  months  old  ;  when  first  received,  it  was  colorless  and  pos- 
sessed a  slight  rancid  odor ;  now  it  is  of  a  pale  amber  color  and 
its  odor  is  very  strong.  Nos.  1,  2  and  3  are  colorless,  2  and  3 
bland  and  inodorous.    No.  1  has  a  slight  rancid  odor,  which  be- 
