Am.  Jour.  Pharm. } 
June,  1885.  J 
Note  on  Glycerin. 
275 
NOTE  ON  GLYCEKIN/ 
By  Henry  Trimble. 
In  the  April  number  of  this  Journal,  page  173,  is  an  abstract  on 
the  use  of  glycei'in  vapor  in  throat  tronl)les.  The  question  has  arisen, 
whether  or  not  the  vapor  of  glycerin  would  be  given  off  when  used  as 
there  recommended,  by  heating  in  a  porcelain  capsule,  or  whether  the 
irritating  decomposition  products  would  be  evolved.  To  determine 
this  about  50  grams  were  heated  in  a  capsule,  with  a  thermometer 
dipping  into  the  liquid.  The  temperature  was  allowed  to  rise  very 
slowly  with  the  following  results:  At  92° C.  vapor  could,  with  some 
difficulty,  be  seen  rising;  at  100° C.  it  was  very  perceptible;  at  130° 
it  was  abundantly  given  off,  rising  as  a  dense  white  smoke.  This  vapor 
was  almost  odorless,  without  the  slightest  irritation,  and  tasted  sweet 
when  drawn  into  the  mouth.  This  evolution  of  vapor  continued  with- 
out the  liquid  in  the  capsule  becoming  dark  until  a  temperature  of 
234°  C.  was  reached.  At  264°  there  was  a  slight  boiling,  but  the 
glycerin  had  so  nearly  all  vaporized  that  the  experiment  was  discon- 
tinued. The  room  was  so  filled  with  vapor  that  one  could  not  dis- 
tinguish objects  clearly  10  feet  away,  yet  none  of  those  working  there 
experienced  any  irritation  or  other  difference  except  the  sweetish  taste 
on  drawing  air  through  the  mouth.  This  experiment  was  repeated 
with  the  same  result,  and  shows  that  when  exposed  to  the  air  ^vith  a 
gradual  application  of  heat  glycerin  will  entirely  vaporize  with  little 
or  no  decomposition.  I  am  aware  that  a  strong  heat  will  cause  it  to 
boil  and  ignite  in  an  open  capsule. 
Another  experiment  was  tried  by  placing  a  large  quantity  of  glycerin 
in  a  flask  attached  to  a  condenser.  The  flask  was  placed  in  a  sand-bath 
and  heat  gradually  applied.  No  change  was  observed,  except  a  very 
small  amount  of  vapor  which  condensed  on  the  sides  of  the  flask,  until 
174°C.  was  reached  when  ebullition  began.  A  small  amount  of  a 
disagreeable  smelling  liquid  came  over,  which  proved  to  be  water  and 
a  small  quantity  of  glycerin,  with  sufficient  decomposition  products  to 
impart  the  odor.  This  moderate  boiling  continued  with  no  further 
change,  until  at  274°  C.  the  flame  was  removed,  as  it  was  evident  the 
boiling  would  continue  with  greater  decomposition  as  the  temperature 
1  Contribution  from  Chemical  Laboratory  of  Philadelphia  College  of 
Pharmacy. 
