338 
Equivalence  of  Drops, 
Am.  Jour.  Pharm 
July,  1880. 
influence  than  anything  else  upon  the  bulk  of  drops  ;  though,  if  this 
be  true,  the  statement  of  Evan  L.  Gmelin,  in  his  "  Handbook,"  that 
"  the  cohesion  of  liquids  is  pretty  nearly  in  proportion  to  their  specific 
gravity,"  cannot  be  accepted  ;  since  alcohol  (specific  gravity  '835)  and 
mercury  (i3'5)  afford  nearly  the  same  number  of  drops  to  the  fluid- 
drachm,  and  chloroform  (specific  gravity  1*480)  yields  a  drop  of  less 
than  one-fourth  the  size  of  a  drop  of  water. 
Summary  of  Results. 
To  sum  up  the  results  of  these  experiments,  as  briefly  as  possible,  it 
may  be  stated  that  the  administration  of  powerful  medicines  by  drops 
is  always  dangerous.  A  single  fluid  may,  under  differing  circumstances, 
give  drops  varying  greatly  in  size  and  weight. 
Much  diversity  is  found  in  the  size  of  drops  from  different  bottles, 
and  a  single  bottle  is  inconstant  in  this  respect.  The  most  constant, 
and  therefore  the  best  bottles  for  dropping  are  those  with  ground  necks 
and  glass  stoppers,  and  wide,  thin,  even  lips.  If  bottle  of  this  kind 
are  used,  each  one  should  be  carefully  tested,  and  marked  with  the  size 
of  its  drops  as  compared  with  a  minim. 
To  drop  from  corks  applied  to  the  outer  edge  of  lips  of  bottles  is 
even  less  accurate  than  using  the  bottles  alone.  Much  better  results 
than  either  may  be  gained  by  the  use  of  droppers;  and  of  those  tested, 
all  of  which  are  in  more  or  less  common  use,  the  best  is  the  Barnes 
dropper.  Yet  it  will  be  seen  that  this  does  not  accomplish  all  that  is 
claimed  for  it,  only  two  out  of  a  dozen  yielding  "  sixty  drops  distilled 
water  to  a  fluidrachm,"  which  is  the  claim  for  superiority  set  forth  on 
each  box  cover. 
Cohesion  exerts  the  greatest  influence  upon  the  bulk  of  drops. 
Temperature  has  little  effect,  and  rapidity  of  dropping,  almost  none. 
The  list  of  officinal  liquids  shows  that  the  largest  drop  was  yielded 
by  syrup  of  gum  arable  (44  to  fs),  and  the  smallest  by  chloroform 
(250  to  ^Z)'  Of  bromine  the  number  of  drops  corresponds  with  chlo- 
roform, but  it  cannot  be  accepted  as  correct,  on  account  of  the  extreme 
volatility  of  the  liquid,  which,  notwithstanding  caution,  and  as  great 
haste  as  was  compatible  with  successful  counting,  caused  the  loss  of  a 
large  percentage. 
Strict  general  rules  cannot  be  laid  down  as  to  the  corresponding  size 
of  drops  of  classes  of  preparations,  though  the  volatile  oils,  tinctures, 
spirits,  oleo-resins  and  fluid  extracts  may  be  grouped  together,  as  yield 
