Am.  Jour.  Pharm. 
October,  1920. 
Estimation  of  Methyl  Alcohol. 
723 
0.25 
0.05 
1-5 
+ 
0.015 
0. 25 
0.05 
1-4 
0 
0 . 014 
0. 10 
0.025 
1 .0 
+ 
0 . 0050 
0. 10 
0.025 
0.9 
0 
0.0045 
0.05 
0.010 
1-3 
+ 
0.0026 
0.05 
0.010 
1 . 2 
0 
0 . 0024 
0.025 
0.005 
I  -3 
+ 
0.0013 
0.025 
0.005 
1 .2 
0 
0.0012 
0.010 
0.001 
2.5 
+ 
0 . 00050 
0.010 
0.001 
2.4 
0 
0 . 00048 
In  the  above  table  are  given  the  concentrations  of  methyl  alcohol 
which  are  completely  oxidized  (so  as  to  give  a  negative  formalde- 
hyde reaction)  by  concentrations  of  persulphate  varying  from  0,001 
to  5  per  cent. 
The  above  table  represents  the  final  results  of  a  detailed  series 
of  experiments,  of  which  one  is  given  in  extenso  to  illustrate  more 
clearly  the  method  employed. 
To  determine  the  concentration  of  the  solution  of  methyl  alcohol 
which  is  just  oxidized  by  a  5  per  cent,  persulphate  solution,  so  that 
no  formaldehyde  is  present  after  heating  the  mixture  for  ten  min- 
utes: 
First  Series : 
5  Cc.  of  this  5  per  cent,  persulphate  solution  + 
5  Cc.  of  I  per  cent,  solution  of  methyl  alcohol 
4  Cc.  of  I  per  cent,  solution  of  methyl  alcohol 
3  Cc.  of  I  per  cent,  solution  of  methyl  alcohol 
2  Cc.  of  I  per  cent,  solution  of  methyl  alcohol 
I  Cc.  of  I  per  cent,  solution  of  methyl  alcohol 
1  Cc.  H2O 
2  Cc.  H2O 
3  Cc.  H2O 
4  Cc.  H2O 
Reaction 
(Formaldehyde) . 
strong  pink 
pink 
pink 
pink 
o 
Hence  the  concentration  of  methyl  alcohol  solution,  5  Cc.  of 
which  is  completely  oxidized  by  5  per  cent,  persulphate,  lies  be- 
tween V5  and      of  one  per  cent. 
To  determine  the  concentration  more  accurately,  the  following 
second  series  of  experiments  was  carried  out: 
Reaction 
(Formaldehyde) . 
5  Cc.  persulphate  solution  -\- 
1.5  Cc.  of  I  per  cent,  solution  of  methyl  alcohol  3 
1.45  Cc.  of  I  per  cent,  solution  of  methyl  alcohol  3 
1.4  Cc.  of  I  per  cent,  solution  of  methyl  alcohol  3 
1.3  Cc.  of  I  per  cent,  solution  of  methyl  alcohol  3 
1.2  Cc.  of  I  per  cent,  solution  of  methyl  alcohol  3 
I.I  Cc.  of  I  per  cent,  solution  of  methyl  alcohol  3 
5  Cc.  H2O  faint  pink 
55  Cc.  H2O  just  pink 
6  Cc.  H2O  o 
7  Cc.  H2O  o 
8  Cc.  H2O  o 
9  Cc.  H2O  o 
