802 
Abstracts  from  Theses. 
(  Am.  Jour.  Phartn. 
1   November,  1920. 
and  the  preparation  of  ethyl  nitrite  made  possible  with  very  simple 
apparatus. 
FREQUENTLY  USED  SATURATED  SOLUTIONS. 
The  dispensing  pharmacist  is  frequently  called  upon  to  prepare 
saturated  solutions  of  certain  salts,  and  is  accustomed  to  depend 
upon  the  solubility  statements  of  the  Pharmacopoeia  as  a  guide. 
These  figures  are  valuable  so  far  as  the  information  goes,  but  do 'not 
show  the  volume  of  the  completed  solution,  and  therefore  are  an 
incomplete  guide  where  a  definite  volume  of  a  saturated  solution 
is  to  be  prepared. 
Lewis  G.  Freeman  in  a  thesis  prepared  in  the  Pharmacy  Labora- 
tory has  undertaken  experiments  to  supply  these  desired  figures 
for  several  salts  often  called  for  in  the  form  of  saturated  solutions. 
In  each  instance  a  definite  weight  of  strictly  U.  S.  P.  salt  was  taken 
(lo  Gm.)  and  the  solubility  checked  in  three  ways.  First  the  exact 
amount  required  for  solutions,  as  stated  by  the  U.  S.  P.,  was  added, 
the  mixture  frequently  agitated  at  25°  C.,  in  a  tube,  graduated  to 
tenths  of  a  Cc,  until  solution  resulted.  It  was  necessary  in  all 
cases  to  add  slightly  more  water,  to  dissolve  the  salt  than  stated  by 
the  Pharmacopoeia.  When  completely  dissolved,  the  final  volume 
was  noted. 
By  the  second  method  the  salt  (10  Gm.)  was  dissolved  in  the 
specified  volume  of  water,  with  the  aid  of  heat,  but  a  slight  additional 
amount  of  water  was  required  to  prevent  crystallization  on  cooling. 
Again  the  volume  was  noted. 
In  the  third  experiment  an  excess  of  the  salt  was  agitated  with 
distilled  water,  at  25  °  C.,  until  the  solution  was  saturated,  the 
mixture  filtered,  and  a  definite  volume  (10  Cc.)  carefully  evaporated. 
The  weight  of  the  salt  obtained  was  then  calculated  for  a  comparative 
basis.  The  average  of  these  figures  was  used  in  the  following 
results. 
The  figures  showing  the  amount  of  salt  and  water  to  take  for 
making  100  Cc.  i  fluidounce,  and  16  fiuidounces  of  a  saturated  solu- 
tion are  calculated  from  the  experiment  with  10  Gm.  of  salt. 
Potassium  Iodide. 
KI  taken,  10  Gm. ...  99  (98.52)  Gm.     451  (450.47)  Grs.    i  Lb.  av.  208  Gr. 
Water  taken,  7.2  Cc .  71  (70.93)  Cc.       340  (340.39)  Min.   11  Fl.  Oz.  166  Min. 
Resulting  volume, 
10.15  Cc   100  Cc.  I  Fl.  Oz.  16  Fl.  Oz. 
