Am.  Jour.  Pharm.  1 
June,  19 17.  -* 
The  Quarterly  Reviezv  on 
285 
standardized.  To  determine  the  amount  of  ozone  in  the  air  of  a 
room,  a  liter  flask  filled  with  water  is  emptied  therein.  The  air 
replaces  the  liquid.  Five  mils  of  the  standard  ferrous  ammonium 
sulphate  solution  is  then  run  into  the  flask  and  gently  agitated.  It 
is  then  at  once  titrated  with  the  standard  permanganate  solution, 
five  mils  of  which  will  equal  to  0.4  Mn.  of  oxygen.  The  statement 
is  made  that  as  little  as  0.00002  gram  of  ozone  may  be  detected  in 
this  way,  since  one  drop  of  the  permanganate  is  sufficient  to  impart 
a  pink  tint  to  five  mils  of  the  ferrous  solution.  That  this  latter  is 
perfectly  stable  towards  atmospheric  oxygen  is  shown  by  the  fact 
that  no  oxidation  can  be  detected  when  20  liters  of  air  free  from 
ozone  is  slowly  bubbled  through  it.  It  is  interesting  to  know  that 
when  large  volumes  of  ozone  have  to  be  dealt  with,  fully  as  good 
results  can  be  gotten  by  employing  standard  solutions  of  ten  times 
the  strength  mentioned  above.  When  this  was  done,  though,  it  was 
noticed  that  the  more  concentrated  standard  solution  of  ferrous 
ammonium  sulphate,  which  contained  39.2  grams  of  the  salt  to  the 
liter,  was  not  so  permanent  as  the  more  dilute  solution  (Comptes 
rend.,  igi/,  164,  430,  through  Pharm.  Journal  and  Pharm.,  April  7, 
1917,  p.  295). 
Influence  of  Carbohydrates  on  the  Accuracy  of  the  Van 
Slyke  Method  in  the  Hydrolysis  of  Casein. — The  presence  of 
carbohydrates  during  the  hydrolysis  of  casein  by  the  method  men- 
tioned above  causes  a  complete  redistribution  of  the  amino-acids, 
which  varies  according  to  the  nature  of  the  carbohydrate.  It  is  very 
marked  in  the  hexone  bases,  and  a  considerable  loss  of  amino- 
nitrogen  also  takes  place  when  the  protein  is  hydrolyzed  in  the  pres- 
ence of  xylan.  Direct  hydrolysis  is,  therefore,  without  reliance 
when  used  for  the  estimation  of  amino-acids  in  feeding  stuffs ;  the 
great  variation  in  the  nature  and  the  amount  of  the  carbohydrates  in 
feed  stuffs  makes  it  impossible  to  establish  factors  of  correction  for 
the  results  (/.  Biol.  Chem,,  1916,  241-249,  through  Analyst,  March, 
1917,  p.  90  ). 
Hydrotropic  Phenomena. — C.  Neuberg  cites  a  number  of  in- 
stances of  this  useful  phenomenon,  which  is  the  property  of  aqueous 
solutions  of  certain  salts  dissolving  certain  other  substances  which  by 
themselves  are  insoluble  in  plain  water.  This  property  or  phe- 
nomenon has  been  termed  hydrotropism  and  has  been  made  use  of 
pharmaceutically,  the  caffein  sodiosalicylate  of  the  National  Formu- 
lary being  an  instance.    Among  the  substances  having  this  property 
