36 
Varieties. 
Am.  Jour.  Pharm. 
Jan.,  1878. 
The  higher-boiling  portion  of  the  volitile  acids  contains  small  quantities  of  higher 
homologues,  one  of  which,  C6H10O2,  boiling  at  2040,  was  isolated.  Of  volatile 
fatty  acids  the  following  were  found  :  formic,  acetic,  isobutyric  and  common  valeri- 
anic (isopropylacetic).  The  calcium  salt  of  the  latter  forms  with  calcium  tiglate  a 
molecular  compound  crystallizing,  in  long  needles. — Jour.  Cbem.  Soc,  Nov. 
®< 
Commercial  Oxalic  Acid  Contaminated  with  Sulphuric  Acid.  By  O.  Binder. 
— In  analyzing  oxalate  of  ammonium,  the  author  found  that  it  contained  a  large 
quantity  of  sulphuric  acid.  The  oxalic  acid  used  for  the  preparation  of  the  former 
also  contained  sulphuric  acid  to  the  extent  of  0*4  per  cent.  The  acid  was  present 
in  the  free  state,  enclosed  in  the  crystals,  but  also  as  acid  sulphate.  Wicke  found 
the  same  contamination  in  oxalic  acid  in  1857. — Jour.  Chem.  Soc„  Nov.  1877,  from 
Zeitschr.  Anal.  Chem..  xvi,  334. 
Estimation  of  Nitrous  and  Nitric  Acids.  By  G.  Lunge. —  1.  Estimation  of  Nitric 
Acid. — The  author  finds  that  the  estimation  of  nitric  acid  by  oxidation  of  ferrous 
sulphate  (Pelouze),  determining  the  excess  of  the  latter  by  permanganate,  gives 
accurate  results  ;  he  recommends  adding  20  per  cent,  of  its  weight  of  sulphuric  acid 
to  the  solution  before  heating  with  the  nitrate,  to  facilitate  the  oxidation.  Siewert's 
method,  reduction  in  alkaline  solution  by  zinc  and  iron,  gives  low  and  variable 
results.    Hager's  modification  and  Schulze's  process  are  also  untrustworthy. 
2.  Estimation  of  Nitrous  Acid. — The  methods  were  tested  on  a  solution  of  pure 
silver  nitrite  in  sulphuric  acid.  Feldhaus"'  permanganate  method  gives  good  results, 
but  the  standard  solution  must  not  be  too  strong,  and  the  nitrite  solution  should  be 
added  to  it,  not  'vice  versa,  or  there  will  be  loss  from  the  decomposition  of  the 
nitrous  acid  and  escape  of  nitrogen  dioxide.  It  is  advisable  to  keep  the  solution  at 
40 — 500,  as  at  lower  temperatures  the  reaction  does  not  take  place  instantaneousiy, 
so  that  the  point  of  decolorization  cannot  be  so  accurately  observed.  Gerstenhofer's 
modification  of  the  bichromate  method  does  not  give  equally  good  results,  as  it  is 
difficult  to  observe  the  exact  point  when  all  the  chromate  is  reduced.  The  other 
processes  examined,  namely,  Siewert's,  Hart's  and  Crowder's,  did  not  give  accurate 
or  constant  results. 
3.  Estimation  of  Nitrous  and  Nitric  Acids. — The  nitrous  acid  in  the  mixture  is  first 
determined  by  oxidizing  it  to  nitric  acid  by  standard  permanganate,  and  then  the 
total  quantity  of  nitric  acid  present  in  the  solution  is  estimated  by  means  of  ferrous 
sulphate.  The  amount  of  nitric  acid  originally  present  is  found  by  subtracting 
from  the  result  that  formed  by  the  oxidation  of  the  nitrous  acid. 
4.  Analysis  of  a  "Nitrose." — This  "  nitrose  "  (sulphuric  acid  used  to  absorb  nitrous 
fumes)  from  a  soda  factory,  had  a  density  of  1*691  at  150,  and  was  saturated.  It 
contained  413  grams  N203  in  100  cc,  but  no  nitric  acid.  This  result  differs  from 
those  obtained  by  Winckler,  who  found  nitric  acid  present.  This,  however,  was 
probably  due  to  the  analytical  method  employed  j  for  Winckler  added  the  perman- 
ganate solution  to  the  nitrose,  and  experiments  made  by  the  author  with  a  solution 
