728 
Estimation  of  Methyl  Alcohol. 
Am.  Jour.  Pharm. 
October,  1920. 
The  test-tubes  were  provided  with  corks  containing  short  air- 
condensers,  and  were  then  introduced  into  a  water  bath  containing 
boiUng  water  in  which  they  were  kept  immersed  for  ten  minutes. 
At  the  end  of  this  period  each  mixture  was  shaken,  and  the  formalde- 
hyde test  was  appUed  (using  i  Cc.  of  the  hot  solution)  in  the  manner 
already  given  under  the  description  of  the  determination  of  methyl 
alcohol  in  water.  By  using  persulphate  solutions  of  i,  2,  3,  4,  5 
per  cent.,  an  approximate  estimation  of  the  methyl  alcohol  can  be 
made,  as  will  be  obvious  from  the  table  given  above. 
in  the  following  table  are  given  the  percentages  of  persulphates 
in  5  Cc,  which,  when  mixed  with  5  Cc.  of  the  diluted  methyl  alcohol 
acetone  mixtures,  just  gave  the  positive  reaction  described  above, 
which  corresponds  to  the  end-point. 
Table  III. 
Per  Cent. 
CH3OH  in 
Original 
Mixture. 
20.0 
17-5 
15.0 
12.5 
10. o 
9.0 
Per  Cent. 
Concentration  of 
Persulphate  in 
5  Cc.  Added. 
6 
5 
4 
4.0 
3-2 
2.9 
Per  Cent. 
CHOH  in 
Original 
Mixture. 
Per  Cent. 
Concentration  of 
Persulphate  in 
5  Cc.  Added. 
2.56 
2  .24 
2  .  04 
1-7 
1-45 
The  above  researches  were  carried  out  for  the  Food  Investigation 
Board. 
Conclusions. — (i)  A  method  for  estimation  of  methyl  alcohol 
in  water  is  described,  the  essential  principle  of  which  consists  in 
determining  the  concentration  of  ammonium  persulphate  necessary 
to  destroy  completely  the  formaldehyde  formed  in  the  initial  stages 
of  the  oxidation  process  under  certain  specified  conditions  of  experi- 
ment. For  the  detection  of  formaldehyde  the  method  previously 
described  by  one  of  the  authors  has  been  employed. 
(2)  By  a  slight  modification  of  this  method  the  amount  of  methyl 
alcohol  in  acetone  can  be  estimated. 
(3)  To  determine  the  amount  of  methyl  alcohol  in  ethyl  alcohol, 
the  mixture  of  alcohols  is  partially  oxidized  by  a  relatively  small 
amount  of  persulphate  (the  alcohols  being  in  excess),  and  the  formal- 
dehyde formed  under  these  conditions  is  estimated  colorimetrically. 
Imperial  College  of  Science  and  Technology. 
