Ata:i,meri9Harm'}   Volumetric  Estimation  of  Sulphates.  2$$ 
Phosphates.— 0.5  gm.  NaJiPQ4 +12ILO,  4  c.c.  HQ  (sp.  gr. 
1. 1 2),  40  c.c.  water  and  10  c.c.  N/3  BaCL,  were  mixed  in  a  100  c.c. 
flask,  the  liquid  was  heated  to  boiling,  20  c.c.  water  were  added,  then 
drop  by  drop  with  constant  shaking  a  mixture  of  15  c.c.  ammonia 
water  (sp.  gr.  0.98)  and  2  c.c.  36  per  cent,  acetic  acid  was  added. 
Near  the  end  a  considerable  amount  of  precipitate  appeared  which 
failed  to  redissolve  on  shaking  or  boiling.  There  was  much  phos- 
phate still  in  solution.  Various  other  amounts  of  phosphate  were 
tried  under  the  same  conditions.    The  results  are  given  in  Table  II. 
Blank  0  tests  were  done  in  the  presence  of  various  amounts  of 
phosphate.    The  results  are  given  in  Table  III. 
Table  II. 
Na2HP04+  12H2O  taken 
Precipitate 
0.5  gm  
Considerable. 
0.3  gm  
Small. 
0.25  gm  
Slight. 
0.2  gm  
Slight.  .. 
0.15  gm  
Barely  visible. 
0.1  gm  
None. 
Blank  tests  were  done  in  the  presence  of  HgCL  (0.45  gm. )  and 
Na2B407  +  10  HaO  (0.5  gm.),  respectively.  Neither  substance 
interfered. 
Table  III. 
Na2HP04  +  i2H20  taken 
N/io  Na2S2°3  required 
Per  cent,  error 
0.5  gm. 
21.3  C.C. 
+  6.5 
0.3  gm. 
20.6  C.C. 
>  +3- 
0.25  gm. 
20.3  c.c. 
+  1.5 
0.2  gm. 
20.3  c.c. 
+  1-5 
0.15  gm. 
20.05  c'c- 
+0.25 
0.1  gm. 
20  C.C. 
0 
Iron. — Fe-  is,  of  course,  inadmissible.  Fe  -,  if  present  in  the 
final  titration,  liberates  I  from  KI  and  vitiates  the  result.  Fe  -  • 
may  be  completely  removed  from  the  solution  as  basic  ferric  acetate 
by  boiling  the  liquid  after  adding  the  mixture  of  ammonia  and 
acetic   acid.    Unfortunately  coprecipitation  of   soluble  chromate 
8  By  blank  test  is  to  be  understood  a  test  in  which  equal  volumes  of  the 
KjO^Ot  and  BaCb  solutions  are  taken,  as  in  the  standardization  of  the  BaCb. 
