722 
Estimation  of  Methyl  Alcohol. 
Am.  Jour.  Pharm. 
October,  1920. 
drazine  hydrochloride;  to  these  mixtures  are  then  added  i  Cc.  of  a 
2.5  per  cent,  solution  of  potassium  ferricyanide  and  about  3  Cc. 
of  concentrated  hydrochloric  acid.  It  will  be  found  from  this 
preliminary  series  of  experiments  that  the  concentration  of  methyl 
alcohol  will  lie  between  two  limits — viz.,  sl  higher  limit  corresponding 
to  a  concentration  of  the  persulphate  which  is  sufficient  to  oxidize 
completely  the  formaldehyde  formed  in  the  reaction,  and  a  lower 
limit  in  which  the  concentration  is  insufficient,  and  the  mixture  of 
persulphate  and  methyl  alcohol  solution  still  gives  a  positive  re- 
action for  formaldehyde  after  heating  for  ten  minutes.  A  second 
series  of  experiments  can  then  be  carried  out  in  a  similar  manner  to 
the  first,  mixing  5  Cc.  of  the  methyl  alcohol  solution  with  5  Cc.  of 
persulphate  in  concentrations  varying  only  between  the  two  above- 
mentioned  limits.  The  number  of  mixtures  in  this  series  can  be 
varied  according  to  the  degree  of  accuracy  which  is  desired  in  the 
estimations.  If,  for  example,  it  was  found  that  the  mixture  of  5 
Cc.  methyl  alcohol  solution  mixed  with  5  Cc.  of  4  per  cent,  persul- 
phate gave  a  negative  reaction  for  formaldehyde  in  the  first  series  of 
experiments,  while  the  solution  mixed  with  5  Cc.  of  a  3  per  cent, 
solution  gave  a  positive  reaction,  in  the  second  series  of  experiments 
the  methyl  alcohol  solution  was  mixed  with  ammonium  persulphate 
solutions  varying  only  between  3  and  4  per  cent.  For  each  con- 
centration of  methyl  alcohol,  therefore,  there  corresponds  a  definite 
concentration  of  this  persulphate  which  is  just  sufficient,  under  the 
specified  conditions  of  experiment,  to  oxidize  all  the  formaldehyde 
which  is  formed  in  the  reaction. 
Per  Cent. 
Persulphate 
in  5  Cc.  Used 
for  Oxidation. 
Per  Cent,  of 
Solution  of 
MeOH  Used. 
Tabi^e;  I. 
Cc.  of  This 
Solution  in 
10  Cc.  Mixture. 
Formaldehyde 
Reaction. 
Concentration 
of  MeOH  in 
5  Cc.  Aqueous 
Solution. 
5 
.0 
I  .0 
I 
•45 
+ 
0.29 
5 
.0 
I  .0 
.40 
0 
0.28 
4 
.0 
0.5 
2 
•4 
+ 
0.  24 
4 
.0 
0.5 
2 
•3 
0 
0.23 
3 
.0 
0.25 
3 
■45 
+ 
0. 1725 
3 
.0 
0.25 
3 
.40 
0 
0.  170 
2 
.0 
0.25 
2 
•3 
+ 
0.  115 
2 
.0 
0.25 
2 
•25 
0 
0. II25 
I . 
.0 
0.  I 
2 
.8 
+ 
0.056 
.0 
O.'I 
2 
•7 
0 
0.054 
0, 
5 
0.  I 
I 
•5 
+  . 
0.030 
0. 
5 
0.  I 
I 
•4 
0 
0.028 
