6o8 
Current  Literature. 
[Am.  Jour.  Pharm. 
^    December,  19 17. 
New  Method  for  Determining  Aldehydic  Sugars. — Thje 
process  described  is  iodometric  and  depends  on  the  fact  that  alde- 
hydic sugars  are  oxidized  by  excess  of  iodine  in  presence  of  sodium 
carbonate  with  formation  of  hydriodic  acid  and  the  corresponding 
monobasic  acid  thus  :  RCHO  +  H20  +  I2  =  RCOOH  +  2HI. 
The  reaction  is  not  immediate :  in  practice  about  three  times  the 
theoretical  amount  of  iodine  should  be  used ;  with  glucose,  oxida- 
tion is  complete  in  about  thirty  minutes.  The  excess  of  iodine  is 
then  titrated  in  the  usual  manner  with  thiosulphate  solution.  Simul- 
taneously slight  secondary  oxidations  occur.  To  correct  for  these 
an  experiment  may  be  run  simultaneously  with  a  specimen  of  pure 
sugar  of  the  kind  being  determined  to  obtain  the  correcting  factor. 
The  results  obtained  by  this  method  are  very  accurate.  Ketonic 
and  non-reducing  sugars  are  not  sensibly  oxidized  under  these  con- 
ditions :  aldehydic  sugars  may  therefore  be  determined  by  the 
method  in  their  presence.  In  the  case  of  non-reducing  sugars,  such 
as  sucrose,  however,  the  accuracy  of  the  method  is  influenced  by  the 
proportion  of  these  present.  When  they  greatly  preponderate  over 
the  aldehydic  sugar  the  amount  of  secondary  oxidation  interferes 
with  the  result.  Comparative  results  may  however  be  obtained  by 
checking  against  controls  made  simultaneously  with  the  pure  non- 
reducing  sugar.  Unfortunately  the  reaction  mixture  has  affinities 
for  other  organic  substances  besides  the  aldehydic  sugars ;  hence 
its  practical  application  is  limited.  (J.  Bougault,  Comptes  rend., 
1917,  164,  1,008.) 
Color  Reactions  of  Ammoniacal  Cochineal  and  of  Carmine. 
— An  aqueous  solution  of  ammoniacal  cochineal  gives  a  violet  color 
with  ammonia,  which  is  not  much  modified  on  adding  a  slight  excess 
of  hydrochloric  acid.  If  this  acid  solution  is  shaken  out  with  amyl 
alcohol,  and  the  solvent  is  separated,  and  then  shaken  with  a  little 
aqueous  solution  of  uranium  acetate ;  on  separating  the  watery  layer 
shows  a  fine  amethyst  violet  color.  Under  similar  conditions, 
carmine  affords  an  emerald  green  color.  Sometimes,  commercial 
ammoniacal  cochineal  is  met  with  which  still  contains  some  carmine, 
due  to  the  inc&mplete  transformation  of  the  latter  into  carminamide. 
In  this  case,  the  amyl  alcohol  extract  is  treated  with  an  excess  of 
powdered  calcium  carbonate.  After  a  few  hours'  contact,  the  whole 
is  thrown  on  a  filter,  when  the  liquid  passes  almost  colorless,  The 
precipitate  is  washed  with  a  little  alcohol,  then  treated  with  water. 
