Am.  Jour.  Pharm  ) 
August,  1883.  J 
Size  of  Drops. 
395 
that  it  seems  but  propei  that  attention  should  be  called  to  it.  Other 
conditions  remaining  the  same,  drops  diminish  in  size  as  the  bottle  is 
emptied,  and  to  such  a  degree  that  any  one  can  satisfy  himself  of  the 
fact  in  a  few  minutes.  The  circumstance  which  first  directed  my 
attention  to  the  subject  will  illustrate  also  the  degree  of  variation  in 
size.  It  was  assigned  to  a  student  in  the  laboratory,  as  an  exercise,  to 
ascertain  how  far  drops  might  be  substituted  for  more  precisely  meas- 
ured quantities  of  liquids  in  making  comparative  determinations  for 
domestic  or  even  commercial  purposes.  As  a  preliminary  test  of  the 
degree  of  uniformity  of  results,  the  hardness  of  a  constant  quantity  of 
the  same  sample  of  water  was  destroyed  by  dropping  into  it  standard 
soap  solution,  from  the  same  bottle,  and  the  same  portion  of  the  lip. 
The  number  of  drops  of  course  varied,  but,  after  some  skill  had  been 
acquired  in  using  the  method,  in  a  series  of  experiments,  the  number  of 
drops  reported  as  required,  indicated  regularly  increasing  hardness  for 
four  experiments,  then  a  sudden  diminution,  succeeded  by  regular  in- 
crease. Upon  watching  the  procedure  of  the  student,  there  seemed  to 
be  no  condition  varying  with  the  same  regularity  except  the  amount 
of  liquid  in  the  bottle,  and  consequent  size  of  the  drops;  and  upon 
performing  the  experiments  by  filling  the  bottle  up  to  the  same  mark 
for  each  trial,  the  previous  periodicity  disappeared,  and  the  uniformity 
of  results  was  greater  than  had  been  anticipated.  Subsequent  experi- 
ments with  different  bottles,  and  different  liquids,  demonstrated  that 
the  differences  in  size  of  drops  occasioned  by  the  variation  in  the 
amount  of  liquid  in  a  bottle  were  not  such  as  might  in  all  cases  be 
overlooked  with  prudence  in  the  administration  of  medicines,  and  that 
the  method  of  drops,  untrustworthy  at  best,  was  rendered  much  more 
so  from  this  fact.  Upon  reference  to  an  older  edition  of  the  Dispensa- 
tory, on  hand  at  that  time,  no  allusion  to  the  effect  upon  the  size  of  the 
drops  of  the  amount  of  liquid  in  the  bottle  was  made,  and  it  seemed 
hardly  necessary  to  call  attention  to  a  fact  presumably  known  to  any 
who  had  employed  the  method. 
Since  sending  the  preceding  hastily  prepared  note  upon  the  size  of 
drops  I  have  taken  the  opportunity  to  run  over  the  literature  of  the 
subject  as  given  in  the  American  Journal  of  Pharmacy,  not  then  at 
my  command,  and  am  surprised  that,  with  the  painstaking  character  of 
the  investigation  of  the  conditions  affecting  the  size  of  drops,  this  one 
of  the  degree  of  fullness  of  the  bottle  is  practically  uninvestigated, 
and  left  among  the  undetermined  conditions. 
