Am.  Jour  PhariM.) 
April,  1884.  J 
Dispensing  by  Drops. 
181 
DISPENSING  BY  DROPS. 
By  Albert  Henry  Kinsey,  Ph.G. 
Abstract  from  an  Inaugural  Essay. 
The  size  of  a  drop  generally  depends  upon  and  is  influeuced  by  at 
least  four  conditions.1 
First :  the  self-attraction  that  the  particles  of  liquids  have  for  each 
other. 
Second  :  its  adhesion  to  the  matter  on  which  it  is  formed. 
Third  :  the  shape  of  this  matter. 
Fourth  :  the  physical  relations  existing  between  the  matter  on  which 
it  is  formed,  the  liquid  constituting  the  drop  itself,  and  the  medium 
through  which  it  passes. 
In  my  experiments  I  have  found  that  the  greatest  variance  is  caused 
by  the  third  condition,  viz. :  the  shape  of  the  matter,  to  which  may  be 
added  the  amount  of  surface,  as  it  is  obvious  that  the  more  surface 
the  greater  will  be  the  adhesion,  and  therefore  will  require  more  liquid 
to  overcome  this  force,  and  consequently  will  produce  a  larger  drop. 
This  is  practically  illustrated  below,  when,  in  dropping  from  a  glass 
stopper  the  surface  from  which  the  liquid  has  been  dropped  has  a 
U-shape  and  is  formed  on  the  convex  side,  while  from  a  minim  measure 
it  is  dropped  from  the  concave  side  of  a  V_snaPed  surface,  giving  the 
drop  only  a  very  small  point  to  form  on,  and  therefore  must  be  much 
smaller.  This  is  further  illustrated  in  dropping  from  a  glass  stopper 
held  at  different  angles.  When  held  horizontally  the  drop  is  about 
twice  the  size  of  one  dropped  at  an  angle  of  45  degrees.  The  difference 
is  still  greater  when  a  common  cork  is  taken,  as  it  has  a  more  acute 
angle.  In  the  case  of  tincture  of  opium,  the  drop  from  a  common 
cork,  when  held  in  a  horizontal  position,  was  more  than  twice  as  large 
as  when  held  at  an  angle  of  45  degrees. 
Another  very  important  feature  in  the  matter  of  dropping  is  the 
rapidity  with  which  it  is  done.  It  is  a  well-known  fact  that  the  less 
the  interval  between  successive  drops,  the  larger  they  will  be.  This 
interval  has  been  called  the  growing  time,  and  it  follows  that  if  this 
growing  time  is  constant  in  the  same  liquid,  the  size  of  the  drop  will 
be  the  same. 
'See  also  paper  by  Prof.  C.  F.  Himes,  in  "Amer.  .Jour.  Pharm.,"  p.  394, 
1883.— Editor. 
