Am.  Jour.  Pharm. 
Jan.,  1886. 
Chemistry  of  Nitroglycerol. 
39 
CHEMISTRY  OF  NITROGLYCEROL. 
By  M.  Hay. 
From  the  resemblance  of  nitroglycerol  to  the  nitrites  in  its  physio- 
logical and  therapeutical  properties,  the  author  was  at  first  inclined 
to  regard  it  as  being  a  glyceryl  nitrite  instead  of  a  nitrate,  but  the 
result  of  a  further  investigation  did  not  confirm  this  view.  Railton 
and  others  have  stated  that  nitroglycerol  when  treated  with  alcoholic 
potash  yields  glycerol  and  potassium  nitrate.  This  statement  is  quite 
incorrect ;  the  decomposition  is  of  a  complex  nature.  No  glycerol  is 
obtained,  as  it  is  oxidised  at  the  expense  of  the  N03  groups,  about 
two-thirds  of  which  suffer  reduction  to  the  nitrous  condition,  only 
about  one-third  being  found  as  nitrate  at  the  end  of  the  reaction. 
The  other  products  of  the  reaction  are  potassium  acetate,  oxalate,  and 
formate,  a  small  amount  of  ammonia,  and  a  reddish-brown  resinous 
substance,  which  gives  a  dark  color  to  the  liquid.  Numerous  de- 
terminations of  the  amount  of  nitrite  formed  showed  that  100  parts 
of  nitroglycerol  gave  from  34*14  to  35*24  parts  of  nitrous  anhy- 
dride. (If  two-thirds  of  the  nitrogen  were  converted  into  nitrous 
anhydride  the  amount  would  be  33*48.)  As  it  was  also  found  that 
5  mols.  of  potash  were  required  to  decompose  1  mol.  of  nitroglycerol, 
it  seems  that  the  principal  reaction  may  be  expressed  by  the  equa- 
tion C3H5(0*N02)3  +  5KOH  =  KNG3  +  2KN02  -f  CH3  -COOK  -j- 
H.COOK  -f-  3H20.  The  reaction  is  the  same  either  with  alcoholic 
or  aqueous  potash,  but  is  very  slow  in  the  latter  case,  owing  to  the 
sparing  solubility  of  nitroglycerol  in  water. 
Ammonia  and  alkaline  carbonates  act  in  a  manner  similar  to  pot- 
ash. The  same  may  be  said  for  sodium  hydrogen  phosphate,  but  the 
reaction  is  much  less  powerful,  whilst  sodium  chloride  exerts  hardly 
any  action.  Hydrochloric  acid  acts  less  powerfully  than  alkaline 
carbonates,  and  sulphuric  acid  (1  : 10)  less  powerfully  still,  whilst 
the  concentrated  acid  has  no  action.  De  Vrifs  statement  that  nitro- 
glycerol is  decomposed  by  sulphuretted  hydrogen,  is  not  correct.  The 
alkaline  sulphides  decompose  nitroglycerol,  sulphur  being  precipi- 
tated, and  the  reaction  is  rapid,  and  seems  to  be  promoted  by  the 
sulphur,  yet  the  particular  part  played  by  that  element  has  not  been 
ascertained.  Hot  water  decomposes  nitroglycerol  slowly.  The 
amount  of  nitroglycerol  formed  from  a  given  weight  of  glycerol 
agrees  fairly  with  the  assumption  of  its  being  glyceryl  trinitrate. 
