442  Separation  of  Salicylic  Acid  from  Benzoic  Acid.{An\*™T;^vm- 
odor  of  nitrous  acid,  and  when  it  is  produced  in  a  closed  globe,  the 
interior  rapidly  fills  with  red  gases. 
The  flame  produced  by  exciting  an  induction  coil  by  means  of  an 
alternating  current  was  first  observed  by  Mr.  Spottiswoode,  F.R.S., 
who  described  it  before  the  Royal  Society  in  1880.  It  has  lately 
been  exhibited  on  a  magnificent  scale  at  the  Crystal  Palace,  by 
Messrs.  Siemens  Bros.,  and  by  Messrs.  Swinburne  &  Co.  It  is  not 
known,  however,  that  any  chemical  explanation  of  the  flame  has 
before  now  been  published. —  Chem.  News,  June  24,  1892,  p.  301. 
THE  SEPARATION  OF  SALICYLIC  ACID  FROM  BENZOIC 
/  ACID. 
By  Miss  J.  Schaap. 
There  does  not  at  present  exist  a  good  quantitative  process  for 
the  separation  of  these  acids,  and  hoping  to  effect  this  I  first  tried 
the  precipitation  with  alum.  I  found,  however,  that  the  aluminum 
benzoate  is  not  quite  insoluble  in  water,  so  the  method  is  therefore 
valueless  for  quantitative  purposes.  Better  results  were  obtained 
by  the  following  method  : 
A  few  mixtures,  each  consisting  of  0-25  grm..  of  salicylic  and 
0-25  grm.  of  benzoic  acid,  were  dissolved  in  a  sufficiency  of  hot 
water  and  the  liquids  were  then  allowed  to  cool.  The  salicylic  acid 
was  now  precipitated  by  excess  of  bromine  water,  but  the  question 
had  to  be  decided  whether  it  was  precipitated  as  the  mono-,  di-,  or 
tri-bromo  compound.  I,  therefore,  took  O  25  grm.  of  the  bromo- 
salicylic  acid  and  estimated  the  bromine  by  Fresenius'  lime 
method.  The  nitric  acid  used  was  free  from  chlorine,  but  the  lime 
was  not,  so  a  check  had  to  be  made.  Allowing  for  the  small  quan- 
tity of  chlorine  in  the  lime,  the  results  in  four  experiments  were, 
respectively:  O  305,  0  315,  o  319  and  0-314  grm.  of  AgBr.  Theory 
requires  0  2 15  grm.  for  the  mono-compound,  0  316  grm.  for  the  di- 
compound,  and  0-374  for  the  tri-compound  ;  so  it  follows  that  the 
precipitate  consisted  of  the  di-compound. 
Another  question  now  arose  whether  the  precipitate  was  suffi- 
ciently insoluble  in  water,  and  also  whether  the  precipitation  was 
complete.  To  solve  this  question  0  25  grm.  of  salicylic  acid  was 
dissolved  in  water  and  precipitated  with  bromine  water.  Having 
found  that  the  bromo-compound  is  very  readily  soluble  in  chloro- 
form, I  concentrated  the  filtrate  at  a  temperature  of  300  and  agitated 
