Am.  Jour.  Pharm.  )  ClUeol  Ul   OH  of  EuCalyptllS.  IOJ 
March,  191o.     J  ' 
is  merely  to  soften  the  hard  mass  and  to  aid  in  the  separation  of 
non-cineol  constituents  of  the  oil.  A  large  excess  of  petroleum 
ether  will  decompose  the  compound. 
The  above  method  is  applicable  directly  to  all  oils  containing 
above  50  per  cent,  of  cineol ;  in  oils  containing  lower  proportions 
of  cineol  the  precipitate  is  not  solid  enough  to  permit  of  convenient 
handling;  and  if  the  cineol  content  drops  below  25  per  cent.,  the 
separation  of  cineol  arsenate  is  not  quantitative.  We  have  found 
that  the  addition  of  an  equal  volume  of  eucalyptol  to  such  oils  (i.e., 
mixing  5  Cc.  of  the  oil  with  5  Cc.  of  eucalyptol)  successfully  over- 
comes this  difficulty;  it  then  only  becomes  necessary  to  subtract 
from  the  volume  of  cineol,  as  observed  in  the  neck  of  the  flask, 
5  Cc,  and  to  multiply  the  difference  by  10,  in  order  to  obtain  the 
percentage  of  cineol  in  the  oil. 
Note. — The  arsenic  acid  may  be  obtained  in  commerce  in  crys- 
talline form,  and  may  be  dissolved  in  water  in  such  proportion  that 
the  resulting  solution  has  the  specific  gravity  of  2.173  at  25 0  (corre- 
sponding approximately  to  85  per  cent,  arsenic  acid),  or  it  may  be 
conveniently  prepared  in  the  laboratory  as  follows : 
Place  in  a  porcelain  evaporating  dish  50  Cc.  nitric  acid  specific 
gravity  1.142,  and  add  60  Gms.  arsenic  trioxide  in  small  portions, 
stirring  continuously ;  after  the  reaction  becomes  less  violent,  heat 
over  Bunsen  burner  until  the  oxidation  is  complete  and  the  excess 
of  nitric  acid  is  evaporated ;  test  for  freedom  from  both  arsenic 
trioxide  and  nitric  acid;  filter  and  evaporate  to  about  100  Gms. 
The  resulting  solution  contains  about  85  per  cent,  of  arsenic  acid 
(H3As04). 
In  order  to  test  the  reliability  of  the  method,  we  have  prepared, 
to  begin  with,  various  mixtures  of  cineol  with  turpentine  oil,  and 
ascertained  their  cineol  content  in  the  manner  above  described,  with 
the  following  results : 
1.  50  vol.  per  cent,  cineol  -f-  50  vol.  per  cent,  turpentine  oil;  found  49.5  per 
cent. ;  50  per  cent,  cineol. 
2.  60  vol.  per  cent,  cineol  +  40  vol.  per  cent,  turpentine  oil ;  found  59  per 
cent. ;  60  per  cent,  cineol. 
3.  75  vol.  per  cent,  cineol  -j-  25  vol.  per  cent,  turpentine  oil ;  found  74  per 
cent. ;  75  per  cent,  cineol. 
As  stated  above,  we  found  that  the  application  of  the  method 
to  mixtures  containing  less  than  50  per  cent,  cineol  is  not  practicable  ; 
and,  since  adding  cineol  to  such  mixtures  would  have  amounted 
