422  Ammonia-Free  Distilled  Water.  {^^vST* 
legion.  I  first  commenced  to  use  this  reagent  for  testing  vitriol  exits* 
it  1873  ;  but  its  application  then  was  very  limited  as  I  had  to  make  my 
own,  and  a  perfectly  pure  peroxide  of  barium  is  not  a  very  easy  thing, 
to  make.  In  those  days  peroxide  of  hydrogen  was  looked  upon  as  a 
sort  of  rara  avis,  to  be  found  only  in  the  laboratories  of  schools  of 
chemistry,  and  its  use  was  not  much  extended  until  a  pure  peroxide  of 
hydrogen  entered  the  market  as  a  commercial  article,  to  be  bought  and 
sold  in  the  same  way  as  other  reagents. 
Heaton  Chapel^  May  12,  1879. 
—  Cbe?n.  News  [Lond.],  May  23,  1879. 
PREPARATION  of  AMMONIA-FREE  DISTILLED  WATER. 
By  J.  S.  Thomson. 
The  method  of  water  analysis  as  elaborated  by  Messrs.  Wanklynand 
Chapman  leaves  but  little  to  be  desired  in  the  matter  of  simplicity. 
The  only  part  of  the  process  which  is  in  any  degree  tedious  is  the  pre- 
paration of  the  ammonia-free  water.  That  such  is  the  case  is,  I 
think,  clearly  shown  by  the  number  of  suggestions  which  have  from 
time  to  time  been  made  with  the  object  of  either  doing  away  with  dis- 
tillation in  its  preparation  altogether  or  of  at  least  securing  a  larger 
proportion  of  the  distillate  fit  for  use  in  the  process  of  analysis  than  is. 
usually  the  case.  These  various  processes,  although  no  doubt  very 
ingenious,  have  never  come  into  general  use,  chemists  still  preferring 
to  prepare  the  water  by  the  original  progress,  tedious  though  it  be.  The 
process  about  to  be  described  appears  to  be  free  from  the  objections 
commonly  argued  against  the  earlier  ones,  and  at  the  same  time  it  has 
the  advantage  that  the  original  cost  of  the  necessary  apparatus  is  but 
small. 
The  following  modification  of  the  distilling  apparatus  commonly 
found  in  laboratories  at  once  provides  a  simple  means  of  securing  a 
practically  unlimited  supply  of  ammonia-free  water  and  at  the  same  time 
demands  little  or  no  attention.  The  tube  which  conducts  the  water 
vapor  from  the  still  or  boiler  in  place  of  being  connected  directly  with 
the  worm  or  condenser  pipe,  is  made  to  enter  at  the  bottom  of  a  large 
iron  drum  (say  10  gallons),  while  the  top  of  the  drum  is  connected 
with  the  worm  pipe  in  the  ordinary  manner.  The  drum,  which  is 
freely  exposed  to  the  atmosphere,  condenses  a  portion  of  the  aqueous 
