Am.  Jour.  Pharm. 
March,  1921. 
Urethanes  of  Thymol  and  Carvacrol. 
211 
This  last  derivative  behaved  very  badly,  yielding  an  exceedingly 
deep  blue  colored  amorphous  mass,  which  solidified  very  slowly. 
The  difference  in  color  is  very  striking,  ter  Meer  21  obtained 
the  potassium  salt  of  nitrosophenol  in  a  similar  manner  and  found 
it  to  exhibit  another  form.  It  came  out  as  a  green  amorphous  pre- 
cipitate from  ether,  which,  if  moist,  passed  easily  into  the  red  crystal- 
line form.  Form  alcohol  or  acetone,  it  formed  thin  blue-  green  plates, 
sometimes  in  a  red  form,  probably  of  a  different  water  content. 
Beilstein  22  is  inclined  to  doubt  this  supposition. 
The  loss  at  ioo°  for  the  potassium  derivatives  corresponds 
very  closely  to  that  required  for  one  molecule  of  water  of  crystalliza- 
tion; while  that  for  the  sodium  derivatives  corresponds  somewhat 
to  that  required  for  two  molecules  of  water,  as  ter  Meer  found  for 
the  sodium  derivatives  of  nitrosophenol  itself.  This  difference  does 
not  extend  to  their  aqueous  alkaline  solution  because  both  the  sodium 
and  potassium  derivatives  give  the  same  benzoyl  compound.  The 
difference  may  be  one  of  isomerism  as  two  forms  of  the  phenol 
derivative  are  possible,  or  it  may  represent  an  equilibrium  mixture 
with  only  a  little  of  one  form  present  with  the  other. 
A/=0 
A/-OH 
The  first  (I)  is  the  true  nitros.o  form,  and  the  second  (II)  is  the  "isoni- 
troso"  or  oxime  type. 
Structure  of  Metallic  Nitroso  Derivatives. — The  true  nitroso 
form  of  these  phenols  is  supposed  to  exist,  because  the  mixture 
containing  nitrous  acid  in  their  preparation  may  be  bright  blue  or 
greenish.   On  the  other  hand,  the  blue  and  red  salts  or  alkali  deriva- 
21  ter  Meer,  Ber.,  8  (1875),  p.  622. 
22  Beilstein,  3d  ed.,  vol.  II,  pj  678. 
