194 
ON  PERM  SUBCARBONAS. 
with  warm  water,  particular  care  being  taken  in  the  washing  to 
remove  all  the  soluble  salts.  It  was  then  dried  between  folds 
of  bibulous  paper  at  different  temperatures;  a  portion  at  the 
ordinary  temperature  of  60°  F.,  a  second  quantity  at  a  sand  bath 
heat  of  160°  to  175°  F.,  and  a  third  at  a  boiling  water  bath  heat. 
When  these  different  specimens  of  subcarbonate  were 
thoroughly  dried,  they  were  reduced  to  powder  and  treated, 
45  grs.  of  each,  with  132  grs.  of  muriatic  acid,  (which  is  the  pro- 
portion for  the  tincture  directed  in  the  XL  S.  Pharmacopoeia,) 
and  gently  heated.  The  acid  was  found  to  be  of  officinal 
strength,  specific  gravity  146. 
All  the  specimens  were  soluble  to  some  extent,  but  differed 
greatly  in  their  respective  degrees  of  solubility. 
The  portion  dried  at  the  temperature  of  60°  F.  was  much 
the  most  soluble,  next  in  this  respect  was  that  dried  at  the  sand 
bath  heat,  while  the  water  bath  temperature  had  rendered  the 
powder  still  more  insoluble. 
To  determine  their  proportionate  solubilities  definitely,  tinc- 
tures were  made  by  adding  to  each  solution  285  grs.  of  alcohol, 
which  was  found  to  be  the  proportion  ordered  in  the  Pharma- 
copoeia. These  tinctures  were  thrown  upon  accurately  weighed 
filters  and  the  insoluble  portions  carefully  washed  with  alcohol. 
The  filters  were  then  dried,  and  when  weighed  with  the  pre- 
cipitates the  resulting  insoluble  portions  from  the  quantities 
used  determined  to  be, 
Residue  of  specimen  dried  at  60°  F.    3-2  grs. 
160v  to  175°  F.    8-3  grs. 
"  "  "      water  bath  9-4  grs. 
Experiment  2d.  Saturated  solutions  of  sulphate  of  iron  and 
carbonate  of  soda,  in  the  same  proportion  as  before,  were  mixed 
at  a  temperature  of  150°  F.  The  resulting  precipitate,  as  in 
the  former  case,  was  washed  carefully,  and  dried  between  folds 
of  paper  at  the  different  temperatures  of  60°  F.,  sand  bath  heat 
of  160°  to  175°  F.,  and  the  water  bath  heat. 
When  dried  and  powdered,  the  different  specimens  were 
treated  with  muriatic  acid  in  the  proportion  of  45  grs.  of  the 
carbonate  to  132  grs.  of  acid,  and  exhibited  generally  a  better 
degree  of  solubility  than  in  the  former  instance.  The  different 
modes  of  drying,  however,  modified  the   solubilities  of  the 
