256  Oxidation  of  Carbon  Compounds.  {^^Mayri^''"'' 
potassium  permanganate.  The  cylinders  were  allowed  to  remain  in 
diffused  light  at  about  15°,  and  10  minutes  after  the  permanganate 
had  been  added  to  the  alcohol,  the  latter  was  run  into  10  cc.  of 
the  indigocarmine  solution  until  the  color  of  the  latter  changed  to 
yellow.  Two  minutes  later,  the  other  solution  was  treated  in  the  same 
way.  A  simple  calculation  gives  the  quantity  of  oxygen  absorbed  by 
each  substance  under  conditions  which  are  strictly  comparable,  except 
that  the  weights  of  the  substances  are  not  identical.  The  second  solu- 
tion is  diluted  to  a  suitable  extent,  and  after  two  or  three  comparative 
experiments,  it  is  easy  to  calculate  the  amount  of  water  to  be  added  to- 
the  second  substance,  in  order  that  the  quantity  of  oxygen  absorbed 
may  be  the  same  in  both  cylinders,  and  from  this  we  get  the  weight  p 
of  the  substance  which  will  absorb  as  much  oxygen  in  a  given  time  as 
1  gram  of  ethyl  alcohol.    If  the  two  numbers  1  and  -  are  not  actually 
P 
proportional  to  the  rates  of  oxidation  of  equal  weights  of  the  two  sub- 
stances, they  are  of  the  same  order,  and  may  be  regarded  as  coefficients 
of  the  relative  rates  of  oxidation  of  the  various  compounds. 
A  large  number  of  substances  were  examined,  and  the  rates  of  oxida- 
tion vary  from  0.2  in  the  case  of  saccharose  to  10,000  in  the  case  of 
pyrogallol ;  next  in  order  to  pyrogallol  comes  catechol,  quinol,  and 
resorcinol,  with  5000,  3333,  and  2000  respectively,  phenol  786*0, 
«-naphthol  769'00,  and  /9-naphthol  666*0.  Hydrocarbons,  sugars,  alco- 
hols of  the  ethyl  series,  and  acids  of  the  acetic  and  benzoic  series,  have 
much  lower  rates,  varying  from  1*0  to  6*0.  Ether  and  alcohol  show 
identical  velocities. 
Determinations  of  the  rate  of  oxidation  may  be  used  to  determine 
the  class  to  which  a  substance  belongs,  and  also  to  detect  impurities  in 
such  compounds  as  acetone.  The  constitution  of  compounds  affects  the 
rate  of  oxidation  more  than  their  composition.  Other  conditions 
being  the  same,  a  saturated  compound  is  less  active  than  a  non-satu- 
rated compound.  Substances  of  the  same  chemical  function  show 
comparable  rates  of  oxidation.  The  aldehyde  function  is  more  active 
than  the  alcoholic,  and  the  phenolic  function  shows  a  very  much 
greater  activity.  The  rates  of  oxidation  of  isomerides  are  not  the 
same.  In  the  case  of  the  dihydroxybenzenes  and  the  toluidins,  the 
ortho-derivative  absorbs  the  most  oxygen,  and  the  meta-derivative  the 
least,  the  para-derivative  occupying  an  intermediate  position. 
