Determination  of  Boric  Acid.      {  Afanl°a^  ^r7f' 
its  form  when  dropped  on  a  piece  of  cold  marble,  or  when  a  small 
amount  is  poured  into  cold  water.  Remove  from  the  fire,  cool  in  a 
capacious  vessel,  and  then  stir  in  the  powdered  mastic.  In  this  con- 
nection it  may  be  stated  that  an  item  of  great  interest  to  me  was  the 
numberless  forms  of  sweets  and  cakes  the  Oriental  people  consume. 
NOTE  ON  THE  DETERMINATION  OF  BORIC  ACID  BY 
TITRATION  IN  THE  PRESENCE  OF  GLYCEROL. 
By  B.  H.  St.  John. 
The  method  usually  given  for  the  titration  of  boric  acid  is  as 
follows : 
Add  methyl  orange  and  neutralize  with  normal  sulfuric  acid,  add- 
ing a  few  drops  in  excess,  then  boil  to  expel  carbon  dioxide,  cool  and 
exactly  neutralize  with  N/io  sodium  hydroxide  solution.  Enough 
glycerin  is  then  added  so  that  the  solution  shall  contain  at  least  30 
per  cent,  and  the  solution  titrated  to  a  pink  color  with  phenolphtha- 
lein. 
In  the  course  of  some  determinations  the  author  noted  that  in 
the  neutralization  to  methyl  orange  with  N/10  sodium  hydroxide 
solution  after  boiling  off  the  C02,  a  very  slow  and  unsatisfactory 
color  change  occurs.  With  the  hope  of  obtaining  a  sharp  color 
change  methyl  red  was  tried  in  place  of  the  methyl  orange.  The 
change  of  color,  as  is  usual  with  methyl  red,  was  quite  sharp  and  en- 
tirely satisfactory. 
The  necessity  then  arose  of  checking  the  accuracy  of  the  results 
obtained  by  using  methyl  red  in  this  titration. 
Accordingly  a  sample  of  boric  acid  was  prepared  by  recrystal- 
lizing  a  commercial  product  from  hot  water.  The  crystals  after 
being  sucked  as  dry  as  possible  on  the  filter  were  dried  over  cone, 
sulfuric  acid. 
Four  solutions  were  prepared  by  dissolving  0.2000  Gm.  of  this 
pure  boric  acid  in  about  30  Cc.  of  water.  To  two  of  these  methyl 
orange  was  added,  and  to  the  other  two  methyl  red.  These  solutions 
appeared  acid  to  methyl  red  but  alkaline  to  methyl  orange.  How- 
ever one  drop  (about  0.03  Cc,  N/10  alkali  sufficed  to  cause  the 
methyl  red  to  indicate  a  neutral  state.    And  0.10  Cc.  N/10  acid 
