Am.  Jour.  Pharm. 
April,  1888. 
Oil  of  Pennyroyal. 
163 
Fkaction  VIII.  (217°-218°)— Specific  gravity  at  16°C.  0.928. 
In  the  first  analysis  0.1372  grams  of  oil,  and  in  the  second  0.1416 
grams  of  oil  were  used  with  the  following  results,  the  formula  corres- 
ponding most  nearly  to  these  being  CioHigO. 
Found. 
Calculated 
for  CioHisO. 
I. 
C.    78.21  per  cent. 
H.  11.62 
0.  10.17 
II. 
78.00  per  cent. 
11.69 
10.31 
Average. 
78.105  per  cent. 
11.655 
10.240  " 
77.922  per  cent. 
11.688  " 
10.390 
100.00  per  cent. 
100.00  per  cent. 
100.000  per  cent. 
100.000  per  cent. 
VAPOR-DENSITIES. — These  were  determined  by  V.  and  C.  Meyer's 
method.  See  "  Berichte  der  deutschen  chemischen  Gesellschaft,"  1877, 
page  2253.  Paraffin  was  used  as  the  bath  and  heated  to  from  1 0°-20°C. 
above  the  boiling  point  of  the  oil.  The  density  of  the  vapor  is  calcu- 
lated by  the  formula  : 
S.  760  (1+0.003665  t)  S.  (1+0.003665  t)  587780. 
(B-W)  Y.  0.001293.  (B-W)  Y. 
This  gives  the  density  in  comparison  with  air,  and  then  by  multiply- 
ing by  14*45  we  get  the  vapor-density  compared  with  hydrogen, 
which  equals  one-half  the  molecular  weight. 
S  denotes  the  amount  of  oil.  T  is  the  temperature  of  the  water. 
B  is  the  barometric  pressure  reduced  to  0°C.  W  is  the  tension  of 
aqueous  vapor,  and  Y  is  the  volume  of  air  displaced.  0*003665  is 
the  coefficient  of  the  thermal  expansion  of  gases.  0*001293  is  the 
weight  of  a  cubic-centimetre  of  air  at  0°C.  and  760  m.m.  pressure. 
587780  is  a  figure  obtained  by  dividing  760  by  0-001293. 
Fraction  VIIL  (217^-218°.)— First  determination  :  0*0467  gms.  of 
oil  were  used  at  759  m.m.  pressure  and  20°  C. ;  7*5  c.c.  of  air  were 
displaced,  the  temperature  of  the  water  being  14°  C,  which  gives  a 
vapor-density  of  75*24-f. 
Second  determination  :  0'0>)74  gms.  of  oil  were  used  at  759  m.m. 
pressure,  and  20°  C. ;  8*8  c.c.  of  air  were  displaced,  the  temperature 
of  the  water  being  16°  C,  which  gives  a  vapor-density  of  79*37.  The 
average  of  these  two  determinations  is  77*31.  The  average  percentage 
composition  obtained  by  ultimate  analysis  is  C  78*105  %  H  11*655  ^  ; 
O  10*240%,  and  the  formula  corresponding  most  nearly  is  CioHigO. 
