40 
Determination  of  Boracic  Acid. 
r  Am.  Jour.  Pharm. 
\      Jan.,  1883. 
Orig.  sub.  10  cc.  borax  solution: a? ::  100: 2/  (per  cent.  B2O3  in  10  cc. 
^of  the  borax  solution). 
Experiments. 
No.  cc.  KMn04 
Number 
Borax 
MnS04 
requ'd  for 
MnS04 
MnS04  in 
Per  cent. 
of 
solution 
solution 
excess  of 
in 
combination  with 
found  of 
Anal. 
used. 
added. 
MnS04. 
excess. 
B2O3. 
B2O3. 
1 
10  cc. 
10  cc. 
6-4  cc. 
•0207  gram. 
•0393  gram. 
36^44 
2 
6-1 
•0198 
•0402 
37^27 
S 
6-3 
•0204 
•0396 
36^71 
4 
6-3 
•0204 
•0396 
36^71 
5 
6-5 
•0210 
•0390 
36^16 
6 
6-4 
•0207 
•0393 
36-44 
7 
6-5 
•0210 
•0390 
36-16 
8 
6-4 
•0207 
•0393 
36-44 
9 
11 
6-2 
•0201 
•0399 
36^99 
10 
11 
6-3 
•0204 
•0396 
36-71 
11 
11 
6-3 
•0204 
•0396 
36-71 
12 
11 
6-4 
•0207 
•0393 
36^44 
13 
11 
6-5 
•0210 
•0390 
36-16 
14 
u 
6-3 
•0204 
•0396 
36-71 
15 
u 
6-4 
•0207 
•0393 
36-44 
16 
u 
6-3 
•0204 
•0396 
36-71 
17 
1 1 
6-5 
•0210 
•0390 
36-16 
18 
ii 
6-4 
•0207 
•0393 
36-44 
The  calculated  percentage  of  B2O3  in  borax  is  36-60^  and  from  the 
experimental  results  it  will  be  observed  that  the  method  can  be  suc- 
cessfully applied  in  the  analysis  of  soluble  borates. 
In  estimating  the  boracic  acid  in  insoluble  borates,  as  tourmaline, 
the  following  course  was  pursued.  The  finely  pulverized  substance 
was  fused  with  a  weighed  quantity  of  pure  sodium  carbonate,  the 
fused  mass  exhausted  with  water,  and  to  the  filtrate  containing  all  the 
sodium  borate,  together  with  some  sodium  silicate  and  aluminate,  was 
added  an  amount  of  pure  ammonium  sulphate  molecularly  equivalent 
to  the  sodium  carbonate.  The  solution  was  then  digested  until  all  the 
ammonia  was  expelled  and  the  volume  of  the  liquid  largely  reduced. 
Any  silicic  acid  or  aluminum  hydrate  which  had  separated  was  now 
filtered  off,  and  the  precipitate  thoroughly  washed  with  hot  water. 
The  solution,  again  reduced  in  volume  and  containing  only  the  borate 
and  sulphate  of  sodium  and  excess  of  ammonium  sulphate,  was  mixed 
with  a  definite  amount  of  a  manganese  sulphate  solution  (strength 
previously  determined),  alcohol  added,  and  after  standing  one-half 
hour  the  borate  was  removed  by  filtration,  the  filtrate  evaporated  to 
dryness  and  the  residue  carefully  ignited  to  expel  the  ammonium  salt. 
