1 84       Recent  Literature  Relating  to  Pharmacy,.  {^l™^™™* 
dry  distillation  the  hydrocarbon  gives  isoprene,  inactive  limonene 
and  heveene.  Isoprene,  on  standing,  polymerizes  into  rubber.  Re- 
cently nitro-derivatives  have  been  obtained  from  rubber,  which 
being  produced  quantitatively  and  soluble  in  many  liquids,  are  useful 
in  the  examination  of  rubber,  and  will  aid  in  further  elucidating  its 
composition.  The  bodies  are,  empirically,  C10H16N2O3  and  C10H16N2O4. 
Rubber  is  probably  a  polymerized  unsaturated  hydrocarbon,  with 
an  open  chain  and  three  double  bonds  for  C10H16.  Kondadoff 
obtained,  synthetically,  a  compound  that  seems  to  be  a  methyl- 
derivative  of  rubber,  thus  making  an  important  step  in  the  synthesis 
of  this  product.  Vulcanization  consists  solely  in  the  addition  of 
sulphur  when  pure  rubber  is  used.  The  condition  of  rubber  can  be 
materially  changed  by  manipulation  between  rollers  :  it  then  becomes 
more  easily  acted  on  by  oxydizing  agents.  The  proportion  of 
sulphur  taken  up  on  vulcanization  ranges  from  that  required  for  the 
formula  C100H160S  to  that  required  for  C100H160S20. — Science,  January 
23»  I9Q3-  Henry  Leffmann. 
GINSENG  CULTURE. 
Bulletin  62,  of  the  Pennsylvania  State  Agricultural  Experiment 
Station,  gives  an  account  of  some  studies  made  at  the  station  to 
determine  whether  ginseng  can  be  grown  profitably  as  a  cultivated 
crop.  The  demand  for  it  by  the  Chinese  seems  to  be  unabated  and 
the  wild  supply  is  annually  diminishing.  The  Pennsylvania  experi- 
ments have  been  going  on  for  five  years,  and  have  resulted  success- 
fully. The  best  crops  were  obtained  from  the  planting  of  two-year- 
old  plants  obtained  from  a  professional  cultivator  of  ginseng.  The 
total  yield  of  the  station's  work  was  5  pounds  and  1  ounce  of  dried 
root,  for  which  a  dealer  paid  at  the  rate  of  $8.50  per  pound.  Fig- 
uring on  this  basis,  it  is  estimated  that  in  five  years  an  acre  would 
yield  a  profit  of  $15,000,  which  does  not  include  any  allowance  for 
the  cost  or  rental  of  land.  The  cultivated  roots  are  larger  than 
those  of  the  wild  plants.  As  yet,  no  insect  injurious  to  the  plant 
has  been  noticed,  but  a  fungus  present  in  the  soil  of  woods  is  at 
times  very  serious.  A  ground-worm  is  also  an  enemy.  The 
details  of  cultivation  and  preparation  for  the  market  are  given  in 
the  bulletin.  H.  L. 
NOTES  ON  ESSENTIAL  OILS. 
While  we  are  frequently  reminded  of  the  purity  of  synthetic  prod- 
ucts and  of  the  cheapness  of  synthetic  perfumes,  as  compared  to 
