THE 
AMERICAN  JOURNAL  OF  PHARMACY. 
MARCH,    1  8  68. 
ON  SULPHITE  OF  MAGNESIA. 
By  Joseph  P.  Remington,  Brooklyn,  N.  Y. 
This  salt  having  been  in  request  lately,  the  authorities  at  the 
writers  command  were  searched  for  a  formula  for  its  preparation. 
It  did  not  appear  to  be  a  frequent  subject  for  examination,  and 
the  published  investigations  seemed  rather  meagre  and  wanting 
in  details. 
The  only  formula  appearing,  was  one  from  Wittstein's  Yiertel- 
jahresschrift,  as  follows  : — "  Sulphite  of  Magnesia  may  be  pre- 
pared by  passing  sulphurous  acid  gas  through  water  holding  car- 
bonate of  magnesia  in  suspension  ;  but  the  salt  so  obtained  is 
not  quite  white.  A  better  way  is  to  dissolve  136  parts  of  crys- 
tallized sulphite  of  soda,  free  from  carbonate  and  sulphate,  in  the 
smallest  quantity  of  hot  water  and  to  filter  into  this  hot  liquid 
a  concentrated  solution  of  123  parts  of  Epsom  Salts,  the  mix- 
ture to  be  stirred  until  cold.  The  mass  of  fine  crystals  which 
form  are  allowed  to  drain  on  a  strainer,  then  pressed  and  dried 
at  a  moderate  heat.    The  product  should  weigh  69  parts." 
It  is  not  an  uncommon  occurrence  to  find  the  sulphite  of  soda 
of  commerce  contaminated  with  sulphate  and  carbonate,  and  if 
made  with  anything  but  a  freshly  prepared  sulphite  of  soda,  the 
yield  would  be  diminished  in  proportion  to  the  extent  of  the 
contamination.  There  is  besides  in  the  above  process  a  small 
yield  of  the  sulphite  of  magnesia  compared  with  the  quantities 
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