68 
Lime  Water. 
i  Am.  Jour.  Pharm 
X    February,  1904. 
The  U.S.P.  method,  using  a  decinormal  volumetric  oxalic  acid 
solution,  has  the  advantage  that  a  sufficiently  accurate  solution  is 
readily  made,  by  any  pharmacist,  while  the  solutions  themselves  are 
more  evenly  proportioned. 
The  testing  of  lime  water  can  readily  be  done  without  the  use  of 
a  burette,  or  other  complicated  apparatus,  a  50  c.c.  metric  graduate 
being  quite  sufficient  to  measure  the  solutions.  The  test  itself  using 
phenolphtalein  as  an  indicator  is  sufficiently  interesting  to  appeal 
to  any  boy  or  apprentice,  and  if  properly  instructed,  the  latter  would 
probably  take  considerable  pride  in  standardizing  his  lime  water. 
To  get  some  additional  data  as  to  the  care  devoted  to  the  making 
of  this  preparation  by  the  local  pharmacists,  a  number  of  samples  of 
lime  water  were  purchased  and  examined.  It  will  not  be  necessary 
to  enumerate  in  detail  the  results  of  our  investigation,  suffice  it  to 
say  that  the  samples  as  purchased  varied  from  0-043  to  0-165  per 
cent,  of  calcium  hydrate,  while  by  far  the  greater  number  of  the 
samples  fell  below  0-148  per  cent.,  the  average  requirement  of  the 
U.S.P.  It  may,  however,  be  of  interest  to  note  that  one-half  of  the 
samples  contained  less  than  0-120  per  cent.,  and  one-fourth  of  the 
total,  less  than  0-085  per  cent,  of  calcium  hydrate,  while,  as  noted 
before,  one  sample  contained  as  little  as  o  043  per  cent,  of  the  alkali. 
All  of  the  purchased  samples  contained  appreciable  quantities  of 
soluble  sulphates,  indicating  that  all  had  been  made  with  common 
tap  or  city  water.  One  sample  contained  appreciable  quantities  of 
a  chloride,  and  this,  on  inquiry,  it  was  learned,  had  been  made  from 
oyster-shell  lime  without  separating  the  coarser  particles,  as  directed 
by  the  Pharmacopoeia.  Further  inquiry  in  this  direction  revealed 
the  fact  that  the  available  oyster-shell  lime,  "  Put  up  expressly  for 
pharmacists,"  has  not  been  sufficiently  calcined  and  contains  ap- 
preciable quantities  of  carbonates,  which  in  turn  appear  to  have, 
enclosed,  soluble  chlorides  that  are  not  readily  washed  out  in  the 
ordinary  way.  The  difficulty  can,  of  course,  be  overcome  by  follow- 
ing the  U.S.P.  directions  and  decanting  the  finer  particles  of  calcium 
hydrate  from  the  coarse  lumps  that  usually  consist  of  uncalcined 
carbonate. 
Some  experiments  made  with  so-called  C.  P.  calcium  oxide,  and 
also  with  calcium  oxide  from  marble,  did  not  give  any  appreciably 
better  results  than  those  made  from  ordinary  lime.  In  ordinary 
practice,  therefore,  it  would  be  perfectly  safe  to  use  commercial  lime, 
providing  several  veiy  essential  precautions  are  observed. 
