Am,  Jour.  Pbarm.) 
June,  1911.  i 
Dried  Magiiesmm  Sulphate. 
263 
been  wrapped  in  paper  before  being  packed  in  the  containers.  Two 
of  the  latter  were  composed  of  thick  pasteboard  and  the  other  of 
tin  with  a  close  fitting  cover. 
The  magnesium,  both  in  the  laboratory  specimens  as  prepared 
and  in  the  specimens  as  purchased,  was  weighed  as  magnesium 
pyro-phosphate,  the  method  being  described  in  detail  in  another 
part  of  this  paper.  It  was  found  that  constant  weight  could  not 
be  attained  when  drying  the  commercial  salt  at  100°  (at  least  dur- 
ing no  reasonable  length  of  time),  the  specimens  continuing  to  lose 
weight  very  slowly  even  when  dried  for  several  days.  It  was 
therefore  found  expedient  to  record  the  results  after  drying  for  4 
hours  at  100°. 
The  specimen  bearing  the  label  of  the  Mallinckrodt  Chemical 
Works  contained  67.2  per  cent,  anhydrous  magnesium  sulphate 
and  lost  7.3  per  cent,  of  water.  The  Powers-Weightman- 
Ro^engarten  specimen  contained  64.9  per  cent,  anhydrous  magnesium 
sulphate  and  lost  19.4  per  cent,  on  drying.  The  Merck  specimen 
contained  54.3  per  cent,  anhydrous  magnesium  sulphate  and  lost 
26.1  per  cent,  on  drying.  While  no  claim  for  purity  or  strength 
is  made  upon  the  label  of  this  specimen,  the  product  sold  by  this 
firm  is  described  in  Merck's  Index  (1907)  as  containing  about  2 
molecules  of  water,  corresponding  to  about  77.0  per  cent,  of 
anhydrous  magnesium  sulphate.  The  product  as  actually  sold, 
therefore,  contains  but  about  70.5  per  cent,  of  the  amount  of  anhy- 
drous magnesium  sulphate  claimed  for  it.  The  results  obtained 
for  all  of  the  specimens  examined  are  tabulated  below : 
Laboratory  number  or 
brand. 
Anhydrous  magnesium  sul- 
phate (MgS04) 
Water 
(Loss  in  4  hours  at  ioo°) 
I  (Ph.  G.  V.) 
2 
75.26 
84.68 
3-4 
Not  determined 
M.  C.  W. 
8.2 
67.20 
Not  determined 
7.29 
19.42 
26.16 
P.  W.  R. 
Merck 
6493 
54-27 
Tests  for  heavy  metals  and  for  arsenic  were  made  upon  all  of 
the  specimens  examined  by  methods  described  in  another  portion  of 
this  paper.    The  result  in  each  case  was  negative. 
The  assertion  is  made  in  the  literature  that  dried  magnesium 
