Am.  Jour.  Pharm.  ) 
May,  1910.  / 
Anhydrous  Sodium  Sulphite. 
213 
On  the  other  hand,  anhydrous  sodium  sulphite  was  found,  by 
Hartley  and  Barrett,4  to  he  stable  so  long-  as  it  is  kept  dry,  while 
Kastle  and  Elvove  5  also  found  the  anhydrous  salt  to  show  practically 
no  change  even  when  kept  under  ordinary  conditions  in  glass-stop- 
pered bottles  for  about  a  month.  The  latter  authors  have  also 
pointed  out 0  the  advantage  that  is  gained  by  the  use  of  anhydrous 
sodium  sulphite  in  place  of  the  hydrated  salt  in  the  preparation  of 
Endo's  7  medium,  and  in  this  connection  have  also  described  a  modi- 
fication of  Hartley  and  Barrett's  method  for  the  preparation  of 
anhydrous  sodium  sulphite  which  increases  the  yield  and  makes  it 
of  greater  general  convenience  to  carry  out.  Likewise,  the  marked 
difference  in  the  stability  of  anhydrous  sodium  sulphite,  as  compared 
with  the  hydrated  salt  (Na2S03.7H20) ,  may  be  seen  from  the 
results  obtained  in  the  examination  of  commercial  samples  of  these 
salts.  Thus,  a  sample  of  the  anhydrous  sodium  sulphite,  obtained 
from  the  same  firm  that  supplied  the  hydrated  sodium  sulphite 
which,  according  to  the  analysis  above  mentioned,  contained  only 
22.05  Per  cent,  of  Na2S03,  was  found  to  be  96.5  per  cent,  pure 
Na2S03.  In  fact,  even  the  poorest  of  the  samples  of  anhydrous 
sodium  sulphite  examined  was  found  to  contain  over  91  per  cent, 
of  available  Na2SO,3,  as  may  be  seen  from  the  results  given  in 
Table  I. 
That  the  anhydrous  sodium  sulphite  remains  practically  unal- 
tered, even  when  kept  for  a  comparatively  long  time,  under  ordinary 
conditions,  in  glass-stoppered  bottles,  may  be  seen  from  the  results 
given  in  Table  II. 
These  results  show,  therefore,  that  even  after  having  stood  for 
over  seven  months,  under  ordinary  conditions,  in  glass-stoppered 
bottles,  none  of  the  samples  of  anhydrous  sodium  sulphite  examined, 
altered  in  its  available  sulphite  to  an  extent  which  might  be  con- 
sidered practically  significant  when  compared  with  what  takes 
place,  under  similar  conditions,  in  the  case  of  the  hydrated  salt. 
It  would  seem  advisable,  therefore,  that  in  the  next  revision  of  the 
U.S. P.,  anhydrous  sodium  sulphite  be  substituted  for  the  hydrated 
variety  given  in  the  present  U.S. P. ;  and  as  the  results  given 
in  Table  I  show  that  several  firms  now  supply  anhydrous  sodium 
4  Jour.  Chem.  Soc,  Trans.,  95,  1178-85  (1909). 
5  hoc.  cit. 
6  Loc.  cit. 
7  Centralbl.  f.  Bakt.,  Orig.,  1903-4,  35,  p.  109. 
