Am.  Jour.  Pharm  I 
Oct.,  1878.  j 
New  Test  for  Glycerin. 
483 
A  NEW  TEST  FOR  GLYCERIN. 
By  A.  Senier,  M.  D.,  and  A.  J.  G.  Lowe,  Assistants  in  the  Laboratories  of  the 
Pharmaceutical  Society. 
In  a  previous  paper  ("Pharm  Jour.,"  viii,  819)  we  have  shown  that 
when  certain  acid  borates,  as,  for  example,  ordinary  sodium  biborate, 
are  dissolved  by  glycerin,  the  glycerin  does  not  act  simply  as  a  solvent. 
We  found  that  acid  was  evolved,  which  was  probably  free  boracic 
acid,  and  that  there  remained  behind  more  basic  borates,  having  a  con- 
stitution between  mono-  and  bi-borates.  Klein  (u  Compt.  rend.,"  lxxxvi, 
826)  says  that  with  acid  borates  mannite  forms  conjugated  acids.  He 
describes  briefly  some  compounds  obtained,  and  then  says  that  similar 
reactions  take  place  in  the  case  of  glycerin,  erythrite  and  certain 
other  polyatomic  alcohols.  It  is  true  that  mannite,  erythrite,  etc., 
evolve  acid  with  sodium  biborate  in  the  same  manner  as  glycerin,  but 
the  reactions  are  probably  not  the  same.  The  test  which  we  are  about 
to  describe  is  not  given  by  mannite,  glucose,  etc.,  although  it  is  readily 
obtained  from  glycerin,  erythrite,  and  apparently  from  glycol.  We 
are  at  present  investigating  this  reaction  more  fully.  It  is  interesting, 
however,  to  note  here,  that  while  we  find  the  action  of  glycerin  and 
erythrite  to  differ  from  the  action  of  mannite  and  glucose,  Klein  also 
finds  the  action  upon  polarized  light  different  in  the  case  of  the  two 
former,  from  what  it  is  in  that  of  the  latter.  The  well-known  green 
color  which  free  boracic  acid  imparts  to  flame  is  usually  obtained  in  the 
case  of  borates  by  the  use  of  a  stronger  acid,  but  lies  ("  Chem.  News," 
xxxv,  204)  suggests  that  glycerin  may  advantageously  be  substituted 
for  the  acid.  The  glycerin  test  for  boracic  acid  involves,  of  course, 
the  reaction  which  we  have  just  discussed. 
It  occurred  to  us  that  this  reaction  might  also  be  employed  as  a  test 
for  glycerin,  but  before  we  describe  the  method  of  applying  it  to  that 
end,  it  will  be  convenient  to  discuss  briefly  its  limits  as  regards  other 
bodies.  As  might  be  anticipated  from  what  we  have  said,  monoborates 
do  not  give  this  reaction,  at  least  that  is  the  case  with  sodium  mono* 
borate.  A  considerable  quantity  of  alkali  interferes  with  the  test, 
doubtless  by  neutralizing  and  fixing  the  acid  set  free.  Again,  a  large 
excess  of  borax  itself  prevents  the  appearance  of  the  green  color  in 
the  flame.  This  action  of  a  large  excess  of  borax  is  interesting.  Now 
as  to  bodies  which  may  be  mistaken  for  glycerin.  Acids  give  the 
same  result  to  flame  as  glycerin,  and  hence  the  solution  to  be  tested 
