486 
New  Test  for  Glycerin, 
S  Am.  Jour.  Pharm. 
\       Oct.,  1878. 
glycerin  similarly  treated  gave  no  green  color.  The  fat  of  milk  like- 
wise gave  no  color  reaction. 
Glycerin  in  Treacle. — 50  cc.  of  treacle,  in  which  was  dissolved  by 
aid  of  heat  and  agitation  5  per  cent,  of  glycerin,  were,  while  warm, 
well  agitated  with  absolute  alcohol.  The  mixture  was  set  aside,  and 
allowed  to  cool  and  separate.  The  alcoholic  solution  was  then 
decanted,  and  evaporated  over  a  water-bath  to  dryness.  This  residue 
was  treated  with  50  cc.  of  absolute  alcohol  in  the  usual  way,  and  the 
alcoholic  solution  so  obtained  evaporated  over  a  water-bath  to  dryness. 
This  second  residue  was  treated  in  the  same  way  with  25  cc.  of 
absolute  alcohol,  and  the  solution  obtained  was  evaporated  as  before. 
The  residue  was  diluted  with  a  few  drops  of  water,  and  the  solution 
made  faintly  alkaline.  Tested,  it  gave  the  green  color  distinctly.  A 
1  per  cent,  solution  failed  to  give  the  reaction,  thus  showing  at  the 
same  time  that  treacle  itself  treated  in  this  way  is  incapable  of  produc- 
ing the  green  color. 
It  may  be  said  then  of  the  test  for  glycerin  here  proposed  that  it  is 
practically  characteristic,  and  is  delicate.  It  can  be  easily  applied,  and 
is  not  interfered  with  by  the  presence  of  a  considerable  quantity  of 
foreign  matter.  We  therefore  commend  it  to  trial  by  chemists  as  a 
substitute  for  the  known  tests  for  glycerin,  which  are  not  only  few  but 
objectionable. 
In  conclusion  we  have  to  express  our  indebtedness  to  Mr.  H.  G. 
Greenish  for  valuable  assistance,  and  to  Professor  Attfield  for  kindly 
permitting  these  experiments  to  be  conducted  in  the  Laboratories  of 
the  Pharmaceutical  Society. 
Authors'  Note. — In  the  discussion  which  followed  the  reading  of 
the  above  paper  our  attention  was  directed  to  the  fact  investigated  by 
Woodcock  ("Jour.  Chem.  Soc,"  xxiv,  785),  that  ammoniacal  salts 
have  the  power  of  decomposing  borax  and  liberating  boracic  acid.  It 
was  suggested  that  these  salts  might  be  mistaken  for  glycerin  unless 
further  precautions  were  taken.    We  find  this  to  be  the  case. 
Substances  to  be  examined  for  glycerin  by  the  test  we  have  suggested 
should  be  first  tested  for  ammonia,  and  should  this  be  present  the  above 
methods  must  be  so  modified  as  to  secure  its  complete  exclusion.  To 
determine  the  presence  of  ammonium  salts,  sodium  carbonate,  and  in 
some  cases  the  Nessler  reagent,  should  be  employed.    The  following 
