Am.  Jour.  Pharm. 
February.  1904. 
A  Basic  Reaction  of  Aldehydes, 
87 
The  method  was  further  checked  by  using  some  pure,  well-crys- 
tallized vanillin  (M.  P.,  8i°  C).  The  phenolic  hydroxyl  of  the 
vanillin  was  first  neutralized  with  a  little  caustic  potash  solution 
until  it  became  a  faint  pink,  using  a  little  rosolic  acid,  sulphite  solution 
added  and  titrated  hot  with  N/2HCI,  having  first  neutralized  the 
sulphite  solution  at  water-bath  temperature  as  in  the  case  of  citraL 
This  was  a  rough  check  on  the  method,  but  as  the  vanillin  had  not 
been  specially  purified  further  examination  of  the  reaction  with 
vanillin,  vanilla  extract,  and  samples  of  vanillin  mixed  with  coumain 
and  acetanilid  will  be  undertaken. 
The  reaction  is  almost  complete  in  the  cold  with  vanillin  and 
merely  needs  heat  to  complete  the  reaction  more  quickly.  Stand- 
ing a  short  time  might  have  given  the  same  results. 
The  reaction  seems  to  be  immediate  and  complete  with  fatty  alde- 
hydes. It  will  indicate  the  presence  of  one  part  of  formaldehyde 
in  1,000,000  parts  of  water  and  when  contained  in  food  products  the 
formaldehyde  can  be  detected  in  a  distillate  of  the  same.  The 
writer  was  able  to  detect  formaldehyde  in  a  solid  product,  partly  made 
from  milk,  by  first  distilling  with  steam,  neutralizing  any  free  acid 
in  the  distillate  with  alkali,  adding  neutral  sulphite  solution  and 
indicated  upon  which  the  presence  of  NaOH  found  in  the  reaction 
is  clearly  shown  and  can  be  accurately  titrated  for  by  means  of  stan- 
dard acid. 
Besides  detecting  and  determining  formaldehyde  in  milk  a  neutral 
sulphite  solution  used  as  s  reagent  is  very  useful. 
The  presence  of  acetone  may  be  detected  in  wood  spirits  and 
determine  acetic  aldehyde  in  grain  spirits.  I  noticed  that  a  sample 
of  grain  alcohol,  which,  even  after  being  carefully  distilled  over 
lime,  gave  a  very  brown  color  when  made  up  into  alcoholic  potash, 
gave  a  very  strong  red  coloration  when  mixed  with  sulphite  solu- 
tion and  phenolphtalein. 
Acetone  and  higher  ketones  were  found  to  react,  but  further  work 
on  the  various  applications  of  this  reaction  must  be  taken  up  with 
the  various  substances  in  detail. 
Referring  again  to  essential  oils,  the  reaction  seems  to  be  applic- 
able to  any  essential  oil,  the  single  or  predominating  constituent  of 
which  is  known,  such  as  cinnamon,  bitter  almond  oil,  lemon-grass 
oil,  cassia,  etc. 
Calculated. 
Found. 
Vanillin 
100  *oo 
99  00 
