176  laster's  method  of  preparing  sulph.  op  manganese. 
the  sulphate  of  managanese*  prepared  according  to  Laster's  new 
method  contains  no  arsenic,  and  is  otherwise  possessed  of  the 
usual  properties  of  the  pure  salt ;  this  sulphate  can  be  employed 
in  the  preparation  of  the  carbonate,  phosphate,  and  lactate,  by 
the  usual  processes  of  double  decomposition. 
Iodide  of  Manganese. — This  preparation  dissolved  in  syrup 
is  formed,  according  to  the  U.  S.  Dispensatory,  by  dissolving 
iodide  of  potassium  and  sulphate  of  managanese  in  water, 
sweetened  with  syrup ;  and  mixing  the  resulting  solutions ;  by 
double  decomposition,  iodide  of  manganese  and  sulphate  of 
potassa  are  formed,  a  portion  of  the  latter  salt  precipitating 
from  its  sparing  solubility. 
To  prepare  this  iodide  Mr.  Laster  has  devised  the  succeeding 
formula,  either  of  which  he  hopes  will  meet  the  requirements  of 
the  pharmaceutist  and  medical  practitioner  : 
"  Take  of       Iodide  of  Calcium,  grs.  142, 
Sulphate  Manganese,  grs.  86, 
Water,  at  boiling  point,  pint  1. 
Dissolve  the  sulphate  in  one-half  of  the  water  heated  to  the 
boiling  point,  and  the  iodide  in  remainder  ;  mix  the  solutions, 
continue  the  boiling  for  ten  minutes,  and,  after  subsidence  of  the 
precipitate,  and  while  solution  is  warm,  filter  and  evaporate  to 
dryness.  Or, 
Take  of       Iodide  of  Lead,  grs.  220, 
Sulphate  of  Manganese,  grs.  87, 
Water,  ounces,  20. 
Dissolve  the  sulphate  of  managanese  in  the  water  heated  to  the 
boiling  point,  and  add  the  iodide  of  lead  portion-wise,  observing 
to  stir  the  contents  of  the  capsule  after  each  addition;  when  all 
the  iodide  has  been  introduced,  continue  the  boiling  for  fifteen 
minutes,  then  filter  and  evaporate  to  dryness. 
In  the  first  process  the  resultants  of  the  decomposition  are 
iodide  of  manganese  and  the  insoluble  sulphate  of  lime  ;  in  the 
second,  the  same  iodide  is  formed,  and  at  the  same  time  sulphate 
of  lead  is  precipitated ;  the  insoluble  compounds  are  removed 
*  This  remark  is  unjust.  There  is  no  process  given  in  the  United 
States  Pharmacopoeia,  and  the  tests  given  in  the  officinal  list  indicate  a 
pure  salt. — Editor  Amer.  Journ.  Pharm. 
