AmNJov^f77arm  {    New  Method  of  Detecting  Alcohol  557 
sufficient  to  develop,  almost  immediately,  the  blue  reaction  if  alcohol 
be  present.  But  owing  to  heat  acting  in  the  manner  described,  I 
would  recommend  the  test  to  be  first  applied  at  the  ordinary  tempera- 
ture, and  if  it  fails  to  indicate  the  presence  of  alcohol  it  shows  that 
either  the  oil  is  free  from  that  substance,  or  if  any  is  present  the  quan- 
tity must  be  extremely  minute,  and  if  the  latter  is  the  case  it  may  be 
readily  detected  by  slightly  warming  the  mixture,  taking  care,  however, 
that  the  heat  should  not  rise  much  beyond  1200  Fahr.,  which,  if  it 
occurred,  would  .create  some  uncertainty  as  to  the  cause  of  the  blue 
reaction. 
By  means  of  this  test  I  have  ascertained  that  several  samples  of  otto 
of  roses  sold  to  me  as  genuine  were  adulterated  with  more  or  less  alco- 
hol, and  that  a  sample  of  rose  geranium  oil  lately  in  the  market,  which 
was  assured  to  Mr.  Tichborne  as  being  a  genuine  article  and  one  of 
superior  quality,  was  very  largely  adulterated  with  alcohol.  From 
several  experiments  I  have  made  with  the  more  expensive  essential  oils, 
mixing*  them  with  different  proportions  of  alcohol,  I  found  that  where 
they  were  mixed  with  one-twenty-fifth,  one-fiftieth,  or  even  with  one- 
hundredth  part  of  their  volume  of  rectified  spirit  of  wine,  that  its  pre- 
sence could  readily  be  detected  by  this  test,  and  I  have  no  doubt  but 
that  it  is  capable  of  detecting  much  smaller  proportions  of  that  sub- 
stance should  it  be  present  as  an  adulterant  in  different  essential  oils. 
I  should  observe,  that  where  the  oil  from  its  density  will  not  rise 
readily  to  the  surface  of  the  water  after  agitation,  as  occurs  with  a  few 
of  the  volatile  oils,  this  difficulty  I  have  found  may  be  readily  overcome 
by  adding  to  the  contents  of  the  tube  a  little  sulphate  of  magnesia, 
which,  dissolving  in  the  water  and  increasing  its  density,  will,  if  em- 
ployed in  sufficient  quantity,  cause  the  oil  to  rise  to  the  surface,  leaving 
the  watery  portion  below  clear  and  suitable  for  testing  with  the  molyb- 
dic  solution. 
Before  concluding  I  should  also  remark  that  the  oils  themselves  must 
not  be  added  directly  to  the  test  solution,  for  I  find  that  many  of  them 
when  so  treated  after  passing  rapidly  through  various  shades  develop  a 
deep  blue  even  though  they  are  apparently  pure,  and  those  that  do  not 
produce  that  color  give  rise  to  such  dark  shades  of  brown,  olive  or 
black,  as  to  mask  more  or  less  completely  any  blue  coloration  which 
might  be  caused  by  admixture  with  alcohol. 
The  same  I  found  to  be  the  case  to  a  great  extent,  though  acting 
