638 
Improved  Deniges  Test. 
5  Am.  Jour.  Pharm. 
(     Sept.,  1921. 
Phenol — As  noted  by  Scudder,13  phenol  interferes  with  the 
test  to  a  degree  dependent  on  its  concentration.  It  may  probably 
be  adequately  separated  by  distillation  after  addition  of  a  liberal  ex- 
cess of  caustic  alkali. 
Fusel  Oil — This  has  been  stated1*  to  afford  a  slight  false  reac- 
tion after  oxidation.  The  present  writer  obtained  one  sample  of 
"fusel  oil,"  and  two  of  C.  P.  amyl  alcohol  (rectified  fusel  oil),  one 
of  the  latter  being  an  "analyzed  reagent,"  all  from  different  manu- 
facturers. Each  sample  was  made  into  a  io  volume-per  cent,  solu- 
tion in  pure  ethyl  alcohol,  and  the  qualitative  test  was  applied.  The 
heaviest  color  was  given  by  the  presumably  purest  sample,  namely, 
the  "analyzed  reagent."  Upon  making  the  qualitative  test  quantita- 
tive by  running  it  in  comparison  with  known  mixtures  of  methanol 
and  ethyl  alcohol  and  letting  stand  an  hour  or  more,  the  color  pro- 
duced was  found  markedly  fainter  than  the  color  produced  from 
ethyl  alcohol  containing  0.08  per  cent,  methanol.  By  the  regular 
quantitative  test  the  color  was  indistinguishable,  being  clearly  less 
than  the  equivalent  of  o.i  per  cent,  methanol.  Hence  the  present 
writer  has  been  unable  to  demonstrate  interference  by  fusel  oil, 
provided  that  it  be  not  attempted  to  strain  the  test  beyond  the  limit 
recommended,  namely,  0.2  per  cent. 
Acetone — This  ingredient,  constituting  up  to  10  per  cent,  of 
the  "total  alcohol,"  does  not  appear  to  affect  significantly  qualitative 
or  quantitative  results. 
SUMMARY. 
The  Deniges  test  has  been  modified  to  increase  sensitiveness  and 
precision,  and  is  recommended  for  practical  work  in  the  detection 
of,  and  especially  in  the  quantitative  determination  of,  methanol  in 
the  presence  of  ethyl  alcohol,  inasmuch  as  the  possible  normal  pres- 
ence of  methanol  in  alcoholic  products  renders  purely  qualitative  tests 
unsatisfactory.  Though  capable  of  greater  refinement,  the  tests 
are  adjusted  to  a  minimum  limit  of  0.2  per  cent,  methanol  in  total 
alcohol.  Procedures  for  the  removal  of  certain  interfering  sub- 
stances are  outlined. 
13  J.  Am.  Chem.  Soc,  27  (1905),  842. 
"von  Fellenberg,  Biochem.  Z.,  85  (1918),  45;  Salkowski,  Z.  Nahr.- 
Genussm.,  36  (1918),  262. 
