NEW  METHOD  OF  PREPARING   SULPHUROUS  ACID.  353 
mus.  This  coloring  acid,  therefore,  is  a  tannin  for  which  the 
name  of  Xanihotannie  Acid  is  proposed.  On  analyzing  the  lead 
compound,  the  results  obtained  indicate  the  following  composi- 
tion :   3  Pb  0-fC28  H18  C4 — Wittsteins   Viert.  Schrift.  viii., 
1 — 7.  J.  M.  M. 
NEW  METHOD  OF  PREPARING  SULPHUROUS  ACID. 
By  E.  F.  Anthon. 
There  are  various  methods  of  preparing  sulphurous  acid,  of 
which,  however,  those  only  are  usually  employed  which  depend 
on  the  combustion  of  sulphur  (or  iron  pyrites),  or  upon  the  de- 
composition of  heated  concentrated  sulphuric  acid  by  sawdust 
and  the  like,  or  by  metals. 
The  first  of  these  methods  is  certainly  simple  and  cheap,  but 
it  is  not  applicable  in  many  cases.  The  decomposition  of  sul- 
phuric acid  by  copper  or  mercury  is  expensive,  and  also  presents 
other  inconveniences.  The  decomposition  of  sulphuric  acid  by 
chips  of  wood  and  other  organic  matters  is  also  expensive,  be- 
cause in  consequence  of  their  great  volume,  a  great  excess  of 
sulphuric  acid  must  be  employed,  which  escapes  decomposition. 
Moreover,  the  sulphurous  acid  thus  obtained  is  contaminated 
with  more  or  less  carbonic  acid. 
(The  preparation  of  sulphurous  acid  by  decomposition  with 
charcoal,  which  is  easily  effected,  is  passed  over  by  the  author, 
and  consequently  the  question  is  left  unanswered,  whether  the 
preparation  of  sulphurous  acid  by  boiling  sulphuric  acid  with 
sulphur  is  more  convenient  than  this.  It  appears  from  the  ori- 
ginal that  the  fact  that  sulphuric  acid  is  decomposed  by  boiling 
with  sulphur  is  unknown  to  the  author,  and  yet  it  is  now  indica- 
ted in  the  Chemical  Text  books.  The  method  described  by  the 
author  is  consequently  not  new,  and  therefore  only  deserves  fur- 
ther notice,  if  it  be  more  convenient  for  the  preparation  of  sul- 
phurous acid  than  it  was  supposed  to  be. — Ed.  Chem.  Central- 
Matt.) 
The  author  placed 
2  ounces  of  sulphur  in  fragments,  and 
25  ounces  of  concentrated  sulphuric  acid 
