176 
Arts  to  I. 
f  Am.  Jour.  Pharm. 
1      April,  1891. 
been  directed  to  the  iodine  products  of  the  phenols,  resulting  in  the 
introduction  in  practice  of  an  iodine  compound  of  thymol  under  the 
proprietary  name  of  Aristol.  And  it  has  also  been  discovered  that 
similar  products  may  be  produced  with  phenol,  naphthol,  resorcin, 
salicylic  acid  and  carvacrol.  It  must,  however,  be  borne  in  mind 
that  none  of  these  contain  so  large  a  percentage  of  iodine  as  iodo- 
form, and  to  possess  equally  valuable  properties  must  in  a  measure 
depend  upon  the  known  antiseptic  value  of  their  organic  bases. 
The  exact  composition  and  mode  of  manufacture  of  aristol  has  not 
been  published  by  the  manufacturers,  they  contenting  themselves 
with  the  statement  that  it  was  an  iodine  derivative  of  thymol  and 
differed  from  the  formulas  and  products  published  by  various 
investigators. 
J.  Messinger  and  G.  Vortmann,  who  first  reported  upon  these 
iodine  derivatives  of  the  phenols  (Ber.,  xxij,20i2,  see  Journal 
Chem.  Society,  1889,  11 50),  stated  that  their  product,  obtained  by 
adding  a  solution  of  iodine  in  potassium  iodide  to  a  solution  of 
thymol  in  potassium  hydrate,  was  a  brownish-red  amorphous  com- 
pound having  the  composition  of  di-io  do-thymol  (C10H12I2O).  This 
compound,  they  state,  retains  its  color  many  months  when  preserved 
in  the  dry  state  in  the  dark,  but  decomposes  on  exposure  to  light  or 
moisture  with  the  liberation  of  iodine  into  a  yellow  compound,  an 
iodine  derivative,  most  likely  of  dithymol.  This  yellow  substance 
is  also  formed  when  the  brownish-red  '  compound  is  boiled  with 
water,  aqueous  alkalies  or  sulphites  or  thiosulphites.  The  same 
writers  subsequently  proposed  the  adoption  of  this  reaction  for  the 
volumetric  estimation  of  phenols,1  and  state  that  one  molecule  of 
thymol  requires  four  atoms  of  iodine  for  complete  precipitation,  a 
1  The  process  given  for  phenol  is  as  follows:  One  molecule  of  phenol 
requires  6  atoms  of  iodine.  2  to  3  gm.  of  phenol  is  dissolved  in  solution 
of  NaHO  using  at  least  3  molecules  NaHO.  It  is  diluted  to  250  to  500  cc.  and 
5  or  10  cc.  of  this  solution  is  taken  in  a  flask  maintained  at  about  6o° ;  then 
1L  iodine  solution  is  added  until  a  dark  yellow  solution  is  obtained,  which  on 
10 
shaking  forms  a  bright  red  precipitate.  After  cooling  the  solution  is  acidified 
with  dilute  H2S04  and  diluted  to  250  to  500  cc,  filtered  and  an  aliquot  portion 
(100  cc.)  titrated  with  —  sodium  thiosulphate  solution  by  which  excess  of 
10 
iodine  remaining  is  determined.    The  amount  of  iodine  used  X  factor  ^ 
759 '24 
=  0*123518  gives  the  quantity  of  pure  phenol. 
For  Thymol  :    Iodine  precipitates  from  alkaline  solution  of  thymol  a  red 
