^No^embeMsS1"}  Nitro-Glycerin  in  the  Pharmacopoeia.  527 
six  times  the  capacity  of  the  quantity  to  be  made  to  allow  for  the 
copious  effervescence  which  takes  place.  When  the  foregoing 
mixture  has  cooled  to  400  C,  the  solution  of  mercuric  nitrate  is 
added  and  the  temperature  is  raised  gradually  to  6o°  C,  and  main- 
tained until  no  further  evolution  of  gas  is  noticed.  If  it  is  then  agi- 
tated until  cold,  as  usual,  the  resulting  product  will  comply  with  the 
requirements  of  the  Pharmacopoeia. 
Ointment  made  by  theU.  S.  P.  method,  which  has  become  spongy, 
may  be  remedied  by  elevating  the  temperature  to  6o°  C.  and  cool- 
ing with  agitation. 
NITRO-GLYCERIN  IN  THE  PHARMACOPCEIA.  ,  . 
By  J.  B.  NAGEI.VOORT. 
A  dozen  good  pharmaceutical  journals  do  not  mention  the  fact 
that  nitro-glycerin  can  be  washed  out  of  its  alcoholic  solution,  and 
that  a  fairly  accurate  and  practical  quantitative  estimation  of  nitro- 
glycerin in  alcoholic  solutions  can  be  based  upon  this  property. 
The  following  simple  method  does  not  seem  to  have  deserved  a 
place  in  the  hand-books  on  pharmaceutical  chemistry,  either. 
When  it  is  taken  into  consideration  that  it  is  better  to  have  a 
quantitative  estimation  of  some  kind  than  none  at  all,  in  the  case 
of  such  a  powerful  medicine  as  nitro-glycerin,  it  might  appropriately 
be  published  how  I  ascertain,  in  perfect  safety  for  the  manufacturer 
and  myself,  the  percentage  strength  of  the  Pharmacopoeial 
SPIRIT  OF  NITRO-GLYCERIN. 
When  I  remember  that  it  must  be  about  ten  years  since  solutions 
of  nitro-glycerin  were  introduced  into  pharmacy,  this  lack  of  infor- 
mation on  this  subject  is  astonishing,  notwithstanding  the  fact  that 
the  Pharmacopoeia  has  no  better  offer  to  warrant  the  dispenser  that 
he  furnishes  a  I  per  cent,  solution  of  nitro-glycerin,  than  a  clear, 
colorless  liquid,  specific  gravity,  etc. 
As  a  starting-point,  can  safely  be  assumed  the  purchase  of  a  10 
per  cent,  alcoholic  solution  of  nitro-glycerin  from  one  of  the  manu- 
facturers of  dynamite  or  giant  powder.  I  advise  even  to  buy  such 
a  solution  and  dilute  it  to  its  required  strength. 
When  such  a  purchase  is  made  in  the  winter,  one  has  to  know 
very  well  what  he  is  about.  A  few  years  since,  when  a  workingman 
