Am.  Jour.  Pharm. ) 
August,  1902.  I 
Drops  as  Dose  Measures. 
381 
readily  be  verified,  ho  wever,  by  any  one  who  has  access  to  a  reliable 
prescription  scale,  a  number  of  bottles  and  some  distilled  water. 
The  figures  given  here  represent  the  highest  and  lowest  of  the 
results  that  were  obtained.  In  each  case,  upwards  of  ten  experi- 
ments were  made,  the  object  being  to  determine  the  effect  different 
quantities  of  water  would  have  on  the  size  of  the  resulting  drop. 
From  the  writer's  experiments  it  would  appear  that  the  difference 
in  the  space  and  thickness  of  the  lip  of  a  vial  is  a  greater  factor  in 
the  size  of  the  resulting  drop  than  in  the  quantity  of  liquid  that 
the  vial  contains.  In  this  series  the  larger  drops  were  sometimes 
obtained  with  a  vial  nearly  full  to  the  neck,  while  in  some  of  the 
experiments  the  drops  from  a  half-filled  vial  were  the  largest. 
The  observation  made  by  Durand,  and  mentioned  in  his  paper, 
that  the  first  drops  from  a  fresh  dropping  surface  were  the  smallest 
was  found  to  be  correct.  This  is,  of  course,  readily  explained  when 
we  remember  that  the  size  of  the  drop  depends  largely  on  the  area 
from  which  the  drop  grows,  or  on  which  it  is  being  formed,  irre- 
spective of  the  available  amount  of  suriace  from  which  it  might 
grow.  There  are  so  many  factors  that  enter  into  the  possible 
attraction  or  lack  of  attraction  that  a  given  substance  has  for  any 
particular  liquid,  that  we  cannot  enter  into  a  discussion  of  this  subject 
in  a  paper  of  this  kind.  Suffice  it  to  say  that  a  rough  or  ground- 
glass  surface  offers  more  attraction  for  the  spread  of  a  liquid,  and 
would  give  a  larger  and  more  uniform  drop  of  water  than  one  that 
is  quite  smooth.  A  clean  smooth  surface,  however,  would  give 
more  uniform  and  larger  drops  than  one  coated  even  with  the 
slightest  trace  of  fat  or  oil. 
The  amount  of  variation  in  the  weight  of  the  drop,  as  obtained 
from  the  T.  K.  dropper,  Table  No.  41,1s  also  interesting,  particu- 
larly in  view  of  the  tact  that  nearly  all  of  the  recent  drop  experi- 
ments in  Germany  have  been  made  with  dropping  bottles  of  this 
type.  While  it  is  true  that  by  means  of  this  device  drops  are 
readily  and  steadily  formed,  the  great  accuracy  and  uniformity  that 
are  claimed  for  them  are  not  apparent  from  the  results  obtained  by 
the  writer.  From  the  available  data  it  is  evident,  that  before  we 
can  expect  to  lay  down  any  fixed  or  definite  rule  as  to  the  size  and 
weight  of  a  drop  we  must  have  a  device  or  means  by  which  we  can, 
under  various  conditions,  obtain  correlating  results.  There  are,  of 
course,  even  at  the  present  time,  several  ways  by  means  of  which  we 
