528  Nitro-Glycerin  in  the  Pharmacopeia.  {ANoVJember,hi™ 
brought  me  a  gallon  bottle,  filled  with  an  alcoholic  solution  of  nitro- 
glycerin, in  which  laid  at  least  500  cubic  centimetres  of  undissolved 
nitro-glycerin  on  the  bottom,  I  escaped  annihilation  by  a  hair's 
breadth.  With  a  question,  "  I  would  like  to  know  what  that  oil  is  ?" 
he  gave  the  bottle  a  smart  rap  on  my  table,  and  pointed  to  the 
nitro-glycerin  that  had  settled  in  the  cold  weather. 
Cool  a  quantity  of  such  a  10  per  cent,  alcoholic  solution  of  nitro- 
glycerin to  1 50  C.  Take  50  cubic  centimetres  of  it;  pour  this 
quantity  into  2  litres  of  water ;  agitate  the  mixture  and  set  it  aside 
in  a  cool  place  over  night.  (In  cold  weather,  take  care  that  the 
water  cannot  freeze  and  break  the  bottle  so  as  to  endanger  your 
life.) 
The  next  morning,  siphon  off  the  water,  only  leaving  enough  in 
the  bottle  to  transfer  the  nitro-glycerin — which  has  separated  and 
lies  as  a  syrupy  fluid  on  the  bottom — into  a  50  cubic  centimetre 
graduate  which  is  graduated  into  y2  cubic  centimetres.  Use  a  fun- 
nel ;  this  insures  against  loss ;  let  the  funnel  drain. 
If  the  10  per  cent,  alcoholic  solution  of  nitro-glycerin  is  of  the 
required  strength,  there  should  be  about  2-5  cubic  centimetres  of 
nitro-glycerin  in  the  graduate.  I  seldom  have  reason  to  complain 
about  the  strength  of  solutions  sold  as  10  per  cent. 
Since  we  measure,  instead  of  weigh,  our  nitro-glycerin,  its  volume 
has  to  be  multiplied  by  its  specific  gravity,  which  is  i-6o,  in  order 
to  obtain  its  weight.    2,  5  X  1-6  =  4. 
Applying  a  correction  for  the  solubility  of  nitro-glycerin  in  a  large 
quantity  of  water  (Allen  says,  "  Commercial  Organic  Analysis,"  Vol. 
II,  p.  305,  it  is  I  gram  in  800  cubic  centimetres),  it  is  a  simple  calcu- 
lation to  verify  the  fluid  under  examination. 
Dilute  according  to  the  figures  found,  to  pharmacopoeial  strength. 
This  is  more  satisfactory  than  to  believe  a  statement  on  a  label. 
Perhaps  it  is  not  superfluous  to  advise  one  to  pour  the  nitro- 
glycerin which  has  separated,  into  a  well,  creek  or  river,  if  he  does 
not  intend  to  dissolve  it  for  future  use. 
Detroit,  October  3,  1894. 
