462  Experiments  on  Thymol  and  Carbolic  Acid,  {^^^l^t^'^^i^' 
A  dilution  of  1  to  50,000 :  in  fifteen  minutes,  and  with  longer  time 
there  occurred  in  all  solutions  a  black  precipitate. 
b.  Experiments  with  Carbolic  Acid :  There  was  here  at  the  com- 
mencement no  perceptible  change,  and  only  a  slight  reaction  at  the 
end  of  half  an  hour,  whilst  in  two  hours  it  was  not  so  intense  and 
striking  as  with  thymol. 
The  property  of  thymol  immediately  to  reduce  gold  in  aqueous  solu- 
tions can  be  used  as  a  means  of  recognizing  thymol  in  the  presence  of 
carbolic  acid,  as  the  latter  only  reduces  chloride  of  gold  after  a  long- 
time. In  a  solution  of  1  to  20  reduction  does  not  take  place  in  three 
minutes.  Mixtures  of  equal  parts  1  to  1,000  of  carbolic  acid  with  1  to 
2,000  of  thymol  gave  reactions,  also  1  to  1,000  carbolic  acid  with  1  to 
5,000  of  thymol  gave  a  useful  reaction  ;  while  1  to  1,000  carbolic  acid 
with  1  to  10,000  thymol  gave  no  decided  reaction. 
7.  Chloride  of  Platinum. 
This  reagent  was  employed  in  the  same  proportion  as  the  chloride  of 
gold,  only  after  the  addition  of  chloride  of  platinum  the  mixture  was 
heated  to  boiling,  as  while  cold  no  reaction  occurred. 
a.  Experiments  with  Thymol :  1  to  1,000  and  1  to  2,000  :  cloudy  and 
opaque. 
1  to  4,000  and  1  8,000 :  cloudy  and  transparent. 
1  to  16,000  and  1  to  32,000:  became  opalescent,  and  a  faint  opal- 
escence was  visible  in  a  dilution  of  1  to  64,000. 
6.  Experiments  with  Carbolic  Acid :  All  degrees  of  dilution  remained 
clear  after  boiling  and  long  standing,  but  in  the  proportion  of  1  to  1,000 
an  opalescence  was  after  some  time  visible. 
The  results  obtained  with  chloride  of  platinum  must  be  presumed 
to  be  better  for  the  recognition  of  thymol  than  others  previously 
named,  and  the  reagent  is  also  useful  to  detect  thymol  in  the  presence 
of  carbolic  acid,  whilst  concentrated  carbolic  acid,  1  in  20,  for  instance, 
gives  no  reaction.  It  is  possible  to  recognize  thymol  in  mixtures  of  1 
to  20,000. 
8.  Nitric  Acid. 
Five  drops  of  the  officinal  nitric  acid  were  added  to  5  c.c.  of  the 
solutions  of  thymol  and  carbolic  acid  respectively  and  boiled. 
a.  Experiments  with  Thymol:  1  to  1,000:  golden -yellow,  opaque. 
1  to  2,000  :  lemon-yellow,  opaque. 
1  to  4,000  :  light  yellow,  transparent. 
1  to  8,000  :  same,  but  paler  yellow. 
