Am.  Jour  Pharm.  I  Determination  of  Boracic  Acid.  39 
DETERMINATION  OF  BORACIC  ACID. 
By  Edgar  F.  Smith. 
When  a  solution  of  manganese  sulphate  is  added  to  one  of  borax, 
and  to  this  mixture  an  equal  volume  of  alcohol,  there  separates  rapidly 
a  white  flocculent  precipitate  of  manganese  borate,  MnB^Oy,  insoluble 
in  the  alcoholic  liquid.  The  excess  of  manganese  sulphate  remains  in 
solution,  and  can  readily  be  determined  in  the  filtrate  from  the  borate 
after  the  expulsion  of  the  alcohol.  To  ascertain  whether  the  above 
might  be  available  quantitatively,  the  following  solutions  of  definite 
strength  were  prepared  and  the  experiments  recorded. 
1.  A  solution  of  manganese  sulphate,  made  by  dissolving  3  grams 
of  anhydrous  MnSO^  in  250  cc.  HgO.  10  cc.  of  this  solution  would 
then  correspond  to  '0600  gram  MnS04. 
2.  Potassium  permanganate  solution  of  such  strength  that  18*6  cc. 
were  equivalent  to  10  cc.  of  I  or  1  cc.  KMnO^  =  '00324  gram 
MnSO^. 
3.  Borax  solution :  10  grams  well-crystallized  borax  dissolved  in  1 
liter  of  H2O. 
The  manner  of  conducting  each  experiment  was  as  follows :  To 
10  cc.  of  the  borax  solution  were  added  10  cc.  MnS04  solution  and 
an  equal  volume  of  strong  alcohol.  The  whole  was  well  mixed, 
allowed  to  stand,  carefully  covered,  for  one-half  hour,  when  the  man- 
ganese borate  was  filtered  rapidly  (best  with  a  suction  pump)  and 
washed  well  with  alcohol.  The  filtrate  and  washings  were  placed  in 
a  platinum  or  porcelain  dish  and  evaporated  to  dryness  on  a  water- 
bath.  The  residual  manganese  was  then  determined  according  to  Vol- 
hard^s  ^  method  by  dissolving  it  in  water,  adding  zinc  sulphate,  then 
heating  to  almost  boiling,  and  carefully  running  in  potassium  per- 
manganate until  the  liquid  assumed  a  pink  color.  The  quantity  of 
manganese  sulphate  thus  found  and  deducted  from  the  whole  amount 
of  the  salt  added,  gave  a  difference  representing  the  manganese  sul- 
phate which  had  combined  with  the  borax.  After  calculating  the 
amount  of  manganous  oxide  to  which  the  sulphate,  found  by  differ- 
ence, is  equivalent,  the  following  equations  were  employed : 
MnO :  2B2O3  am't  MnO :  correponding  am't  B2O3  (x)  ; 
and 
1 '  Annalen  der  Cliemie,"  198,  p  318. 
