172 
ON  LIQUOR  FERRI  IODIDI. 
heat  will  always  drive  off  a  portion  of  iodine ;  and  much  more 
sesquioxide  of  iron  will  be  found  suspended  in  the  liquid  after 
heating. 
The  use  of  iron  filings  should  be  discarded.  Not  only  that 
they  are  objectionable  on  account  of  the  impurities  which  they 
unavoidably  contain,  but  their  action  on  the  iodine  is  far  too  ra- 
pid, even  when  no  heat  is  applied.  An  admixture  of  brass  fi- 
lings, which  must  have  been  in  use  in  the  coppery  preparation, 
examined  by  Mr.  Maisch  some  years  ago,  is  by  no  means  uncom- 
mon. 
It  is  of  some  importance  that  the  water  employed  should  be 
free  from  organic  matter  and  air.  Distilled  water  is  directed 
to  be  used;  but  I  venture  to  say,  this  direction,  as  in  most  other 
instances,  is  but  rarely  followed.  There  is  somewhat  of  an  ex- 
cuse for  the  scarcity  of  distilled  water  in  the  shops,  from  the 
fact  that  it  costs  far  more  than  would  balance  the  advantages 
derived  from  its  use  in  many  preparations.  But,  why  not  use 
melted  ice  ?  It  is  strange  that  so  excellent  a  substitute  for  dis- 
tilled water  has  hardly  ever  been  mentioned.  The  writer  has 
been  using  it  during  the  whole  summer  for  the  same  purposes, 
and  never  found  it  to  act  in  the  slightest  degree  on  nitrate  of 
silver  or  baryta.  It  is  best  prepared  by  melting  clean,  transpa- 
rent pieces  of  ice  in  a  glass  jar,  and  drawing  off  by  means  of  a 
siphon,  from  what  sediment  may  have  formed  during  melting. 
I  would  recommend  this  to  the  consideration  of  the  Association, 
since,  throughout  the  whole  country,  ice  has  now  become  so 
common  an  article  for  domestic  use,  that  pure  water  will  be 
within  the  reach  of  every  one,  if  its  production  in  the  manner 
indicated  is  once  admitted  as  a  fact. 
The  mixing  of  the  ingredients  should  not  take  place  in  a  porce- 
lain dish,  but  a  glass  flask  or  vial,  since  no  heat  from  without  is 
required  to  induce  their  action  on  each  other.  Of  the  recipes 
published  for  this  preparation,  none  appears  to  answer  so  well 
as  that  given  by  Dr.  Squibb,  (vide  Proceedings  for  1858,)  prin- 
cipally by  the  manner  in  which  the  fresh  solution  is  protected 
from  the  action  of  air  from  without,  and  that  in  the  sugar.  This 
one  cause  of  the  changes,  which  the  saccharine  solution  under- 
goes, is  most  effectually  removed  by  filtering  into  syrup.  But 
not  the  action  of  the  air,  which  afterwards  comes  into  contact 
with  the  liquor,  from  the  surface  downwards.    I  have  as  yet  not 
