112 
Solubility  of  Calcic  Hydrate. 
Am.  Jour.  Pharm. 
Feb.,  1884. 
space  in  the  bath.  The  water  surrounding  the  funnel,  being  always 
at  the  same  temperature  as  that  surrounding  the  flask,  it  was  hardly 
possible  for  any  variation  to  take  place,  but  in  order  to  insure  accuracy 
the  thermometer  was  used  in  the  funnel  as  well  as  in  the  flask.  For 
the  temperatures  above  80 °C.  the  solutions  were  heated  over  the  naked 
flame  and  passed  through  a  funnel,  kept  in  boiling  water.  It  is  exceed- 
ingly difficult,  unless  with  special  appliances,  to  filter  at  the  boiling 
point,  and  I  had  to  be  content  with  what  I  have  described.  Strictly 
speaking,  the  maximum  point  reached  would  be  from  98°  to  99°C. 
For  the  sake  of  convenience,  quantities  by  volume  were  taken,  a 
small  graduated  flask  being  employed  as  a  measure. 
The  amount  of  lime  in  solution  was  ascertained  volumetric-ally,  deci- 
normal  nitric  acid  being  used.  This  acid  is  preferable  to  oxalic,  as 
calcic  nitrate  being  soluble  in  water  there  is  no  danger  of  the  exact 
point  of  neutrality  being  obscured  by  the  presence  of  a  precipitate. 
Calcic  oxide,  perfectly  free  from  all  impurities,  was  made  use  of, 
after  having  been  slaked  with  distilled  water.  Incidentally,  I  may 
remark  that  the  heat  generated  in  "slaking"  the  lime  rose  to  the  very 
high  point  of  205°C. 
The  results  which  were  arrived  at  have  been  tabulated  in  three  ways 
for  the  sake  of  convenience,  and  are  appended.  The  figures  are  in 
each  case  calculated  from  the  mean  of  three  titrations,  but  where 
thought  necessary  corroborative  results  have  been  obtained  by  addi- 
tional experiments. 
It  will  be  observed  that  the  solubilities  are  expressed  in  terms  of 
calcic  oxide.  I  express  them  so,  in  accordance  with  custom,  although 
it  is  apparent  that  the  calcium  exists  in  solution  as  hydrate  and  not  as 
oxide. 
I  am  unwilling  to  close  this  note  without  a  few  words  as  to  its  prac- 
tical bearing  upon  the  liquor  calcis  of  the  British  Pharmacopoeia. 
Repeated  proceedings  have  been  instituted  against  druggists  for  the 
sale  of  defective  lime  water,  and  cases  have  been  reported  where  the 
strength  was  as  low  as  0*1,  0*2  and  0'3  gr.  CaO  per  fluidounce. 
Several  hypotheses  might  be  started  to  account  for  this  state  of  things, 
and  I  shall  briefly  allude  to  one  or  two  of  these. 
In  the  first  place,  it  is  obvious  that  the  variations  of  temperature 
which  naturally  occur  really  exercise  comparatively  little  influence  on 
the  strength  of  lime  water,  for  it  can  rarely  happen  that  the  tempera- 
