156  Some  Notes  on  Essential  Oils.  {^m±^\xm!m' 
The  following  table  of  specific  gravities,  taken  from  the  different 
authoritative  works  mentioned  in  the  first  column,  will  give  a  very- 
fair  idea  of  the  differences  of  opinion  that  exist  on  this  one  and 
most  important  physical  property. 
TABLE  GIVING  VARIATION  IN  SPECIFIC  GRAVITY  OF  DIFFERENT  ESSENTIAL  OILS,  AT 
150  CENTIGRADE  UNLESS  OTHERWISE  NOTED. 
United  States  :  British 
Pharmacopoeia.  Pharmacopoeia. 
German  ^Timits  °\ 
Pharmacopoeia.  ^IZfii, 
Oil  of 
Sitter  Almonds 
Cinnamon1  .  .  . 
Cloves2  
Eucalyptus  .  .  , 
Juniper  Berries 
Lavender .  .  .  . 
Mustard  .  .  .  . 
Peppermint  .  . 
Rose3  
Rosemary  .  .  . 
Sandalwood  .  . 
Wintergreen  .  . 
i '060-1 -070 
1-055-1-065 
1  "o6c— 1  '067 
0-915-0-925 
0-850-0-890 
0-885-0-897 
I"oi8-i"029 
0-900-0  920 
0*865-0-880 
0-895-0-915 
0-  970-0-978 
1-  175-1-185 
1-025-1-035 
Not  below  1-050 
0-910-0-930 
0-  865-0-890 
Not  below  0  885 
1-  018-1-030 
0-900-0-920 
0-856-^*860 
0-900-0-915 
0-975-0-980 
1-055-1-070 
1-072-1-074 
0-865-8-880 
0-  885-0-895 
1-  018-1-025 
0-900-0-910 
Not  under  -900 
0-975-0-985 
1-043-1  070 
1-025-1-070 
1-030-1-074 
o  900-0-930 
0-840-0-911 
0-  870-0-948 
1-  010-1-030 
0-840-0  975 
0-  830-0-954 
oe88o-o'9i5 
o'96o-o'990 
1-  175-1-188 
Gildemeister 
and 
Hoffmann. 
1-052-1-096 
1-050-1 -070 
1-045-1-070 
0-910-0-930 
0-865-0-882 
0-885-0-895 
roi6-ro22 
0-895-0-926 
0-855-0-870 
0-904-0-913 
0-  975-0-980 
1-  180-1-187 
1  British  Pharmacopoeia  specifies  Ceylon  cinnamon. 
2  German  Pharmacopoeia  recognizes  only  eugenol. 
3  This  is  at  200  centigrade,  with  the  exception  of  the  British  Pharmacopoeia,  which  specifies  300. 
A  careful  study  of  the  above  table  will  convince  almost  any  one 
that  there  is  still  much  to  be  learned,  or  definitely  determined,  in  con- 
nection with  these  interesting  compounds.  It  must  be  remembered, 
too,  that  this  is  but  one  of  a  number  of  points  on  which  there  is  a  de- 
cided difference  of  opinion.  But  what  is  stranger  still  is  the  fact  that 
this  difference  of  opinion  is  justified  by  the  difference  in  composition 
of  the  same  oil  coming  from  different  localities,  or  at  times  even  from 
the  same  locality,  depending  on  atmospheric  conditions  or  methods 
of  procedure  in  the  production  of  the  oil. 
It  is  also  true,  however,  that  a  large  amount  of  original  work  is 
being  done  on  the  essential  oils  at  the  present  time,  and  it  is  prob- 
able that  in  the  near  future  the  variations  in  the  physical  properties 
will  be  thoroughly  investigated  and  the  reasons  for  their  variation 
definitely  determined. 
It  is  only  necessary  to  mention  the  names  of  Wallach,  Tiemann, 
Beckmann  or  Gildemeister  in  Germany;  Parry,  Holmes  or  Umney  in 
