PRESERVATION  OF  SYRUP  OF  IODIDE  OF  IRON.  265 
lation,  the  high  heat  required  for  this  process  decomposing  them 
into  some  modification  of  their  original  state. 
The  great  cause  of  irritation  in  glycerin  which  has  not  been 
properly  prepared,  is  the  presence  of  oxalic  acid  and  of  formic 
acid  ;  these  are  produced  by  the  action  of  sulphuric  acid  upon 
the  glycerin,  forming  the  first  mentioned  acid,  and  this  in  its 
turn  acts  upon  the  glycerin,  giving  rise  to  formic  acid,  the  irri- 
tating properties  of  which  are  well  known. 
The  nitrate  of  silver  test  I  have  always  considered  the  most 
reliable.  Glycerin,  which  shows  no  reaction  with  this  salt,  may 
be  considered  suitable  for  all  uses,  as  it  indicates  not  only  the 
the  presence  of  chlorine  or  chlorides,  but  is,  as  well,  reduced  by 
acids  which  may  exist  in  the  glycerin. — I  am,  &c. 
Henry  Bower. 
Philadelphia,  January  16th,  1868. 
—Chemical  News,  Feb.  7, 1868. 
PRESERVATION  OF  SYRUP  OF  IODIDE  OF  IRON. 
By  Thomas  B.  Groves,  F.C.S. 
The  appearance  of  Mr.  Tilden's  paper  on  the  above  subject 
has  suggested  the  publication  of  the  following  note  of  experiments 
in  the  same  direction  made  in  May,  1865. 
Having  heard  expressed  the  opinion  that  syrup  of  iodide  of 
iron  when  made  from  iron  filings  kept  better  than  a  correspond- 
ing syrup  made  from  pure  iron  in  the  form  of  wire,  it  occurred 
to  me  that  such  (supposing  the  statement  to  be  true)  could  only 
arise  from  the  presence,  in  the  syrup,  of  substance  owing  their 
existence  to  the  impurities  usually  found  in  the  iron  from  which 
filings  are  commonly  obtained. 
The  most  prominent  of  these  impurities  and  those  only  likely 
to  be  concerned  in  this  matter  are  phosphorus  and  sulphur, 
which,  when  treated  in  the  presence  of  water,  with  excess  of 
iodine,  form  respectively  phosphoric  and  sulphuric  acids,  accor- 
ding to  the  following  equation  : — 
P+I6+8HO=P05,3HO,5HL 
Query,  then  would  either  or  both  of  these  acids  when  added  to 
t 
