164 
Oil  of  Pennyroyal. 
Am.  Jour,  Pharm, 
April,  1888. 
Half  the  molecular  weight  of  CioH^gO  is  77'00. 
Half  the  molecular  weight  obtained  by 
calculation  from  the  vapor-density  is  77'30. 
Fraction  T.  (220°-225°.)— First  determination  :  0-0406  gms.  of 
oil  were  used  at  767  m.m.  pressure,  and  21°  C. ;  6*5  c.c.  of  air  were 
displaced,  the  temperature  of  the  water  being  22°  C,  which  gives  a 
vapor-density  of  76'88. 
Second  determination:  0-0499  gms.  of  oil  were  used  at  767  mm. 
pressure,  and  22°  C. ;  8-2  c.c.  of  air  were  displaced,  the  temperature 
of  the  water  being  22°  C,  which  gives  a  vapor-density  of  75.05  +  . 
The  average  of  these  two  determinations  is  75-97 +  .  The  percent- 
age composition  obtained  by  ultimate  analysis  is  C  78"503^; 
H  11-189  ^  ;  O  10*308  %,  and  the  formula  corresponding  most  nearly 
to  this  is  CioHj^O. 
Half  the  molecular  weight  of  CioHj^O  is  76-50. 
Half  the  molecular  weight  obtained  by 
calculation  from  the  vapor-density  is  75-97. 
Fraction  11.  (165°-170°.)— 0-0487  gms.  of  oil  were  used  at  759-5 
m.m.  pressure,  and  25°  C. ;  12-2  c.c.  of  air  were  displaced,  the  tem- 
perature of  the  water  being  23°  C.  This  gives  a  vapor-density  of 
50-18  +  . 
The  average  percentage  composition  obtained  by  ultimate  analysis  is 
C  72-106%;  H  12-164%,  and  O  15-730%.  The  formula  cor- 
responding most  nearly  to  this  is  C6H12O. 
Half  the  molecular  weight  of  CgH^gC^  is  50'00. 
Half  the  molecular  weight  obtained  by 
calculation  from  the  vapor-density  is  50*18. 
Polarization.  The  rotatory  power  was  determined  by  a  Wild  polari- 
strobometer  or  shadow  polarimeter;  both  the  100  and  200  millimeter 
tubes  were  used,  but  as  the  former  only  serves  to  determine  whether 
the  substance  is  dextrogyre  or  Isevogyre,  only  the  figures  obtained 
with  the  latter  are  given. 
Original  oil  boiling  from  180°-206°C  +46.0 
Fraction  T.  220°-225°  +45.6 
IX  "    218°-220°C  +44.6 
"  YIII.  217°-218°  +43.6 
VI.  200°-215°  —11.0 
Y.  185°-200°  —20.0 
"     IV.  180°-185°  —25.9 
