78 
Agave  Americana. 
(  Am,  Jour.  Pharin. 
(        Feb.,  1875. 
3.  Fehling's  test  of  the  rise  of  the  temperature  produced  by  mixing 
with  concentrated  sulphuric  acid. 
4.  The  characteristics  of  the  action  of  solution  of  carbonate  of  pot- 
ash on  the  oil. 
Class  IV. — Rape  oils  are  the  border-land  between  drying  and  non- 
drying  oils,  and  are  employed  both  for  burning  and  lubricating.  The 
specific  gravity  varies  from  0*9 12  to  0*916.  It  is  quite  likely  to  be 
adulterated  with  cotton-seed  oil,  which  [i]  increases  the  specific  grav- 
ity (mineral  and  resin  oils  being  proven  absent)  ;  [2]  it  raises  the  treez- 
ing-point  of  rape  oil,  which  is,  when  pure,  perfectly  liquid  at  32^  F. 
The  other  tests  applicable  are  those  for  estimating  the  drying  properties 
of  the  oil,  or  its  tendency  to  gum,  either  by  exposing  on  blotting-paper 
or  in  small  capsules  to  200°  F. 
Class  V  is  represented  by  linseed  oil,  the  drying  oil  proper,  of  specific 
gravity  0*937  at  60°  F.  Mineral  and  resin  oils  must  be  carefully  looked 
for,  and,  in  their  absence,  fish  oils  are  easily  detected  by  smell  or  Cal- 
vert's tests.  Cotton-seed  oil  may  be  recognized  [i]  by  decreasing  the 
specific  gravitv,  [2]  materially  raising  the  point  of  solidification, 
[3]  decreasing  the  drying  properties,  which  can  be  proved  as  above 
indicated. 
Class  VI. —  Fish  oils  have  a  commercial  value  inferior  to  the  other 
oils,  because  of  their  odor  ;  hence  they  are  not  much  liable  to  adultera- 
tion. They  may,  however,  be  mixed  with  each  other,  some  varieties 
being  much  cheaper  than  others.  The  points  to  be  observed  are, 
[i]  looking  for  mineral  and  resin  oil,  [2]  examining  the  drying  proper- 
ties of  the  sample,  [3]  examining  the  viscosity. 
Oleographs,  or  the  figures  formed  by  oils  dropped  on  pure  water, 
do  not  seem  to  have  been  studied  by  Mr.  Coleman.  With  care  and 
practice  thev  mav  be  made  of  considerable  value  in  testing  oils  quickly 
and  easily. — Jour,  of  Jpp.  Chem.^  Dec..,  1874. 
THE  USES  OF  AGAVE  AMERICANA. 
BY   JOHN    R.   JACKSON,  F.L.S., 
Curator  of  the  Museums,  Royal  Gardens,  Kew. 
Some  attention  has  lately  been  drawn  to  the  common  Agave  {Agave 
Americana)  on  account  of  its  supposed  efficacy  as  an  anti-scorbutic.  As 
noticed  in  this  journal  last  week,  General  Sheridan,  whose  name  is  as 
a  household  word  in  the  United  States,  is  said  to  have  used  the  juice 
with  great  success  amongst  his  men,  who  were  suff'ering  from  scurvy 
