164 
varieties. 
Preparation  Valerianic  Acid  from  Fusel  Oil. — Gruneberg  recommends 
the  following  proportions  as  the  most  advantageous.  2|  lbs.  of  bichromate 
of  potash  are  to  be  introduced  into  a  retort,  and4j  lbs.  of  hot  water  poured 
upon  the  salt.  A  cooled  mixture  of  1  lb.  of  fusel  oil  and  4  lbs.  of  sulphuric 
acid  diluted  with  2  lbs.  of  water  is  to  be  allowed  to  flow  very  slowly  and 
in  a  thin  stream  into  the  liquid  in  the  retort,  and  the  whole  is  then  to  be 
distilled.  The  distillation  goes  on  quietly,  and  9  ounces  of  oily  valerianic 
acid  are  obtained. — Silliman's  Journal,  Jan.  1854,  jfrom  Journal  fur  jyrald 
Chemie,  lx.  169. 
Preparation  of"  Pure  Caustic  Potash. — Wqhler  has  given  a  very  simple 
and  elegant  method  of  preparing  caustic  potash  in  a  state  of  chemical 
purity.  One  part  of  pure  saltpetre  in  powder  is  to  be  mixed  with  from 
two  to  three  parts  of  metallic  copper  cut  into  small  pieces,  and  the  whole 
heated  to  a  moderate  red  heat  for  half  an  hour  in  an  iron,  or,  better  still,  in 
a  copper  crucible.  After  cooling,  the  mass  is  to  be  treated  with  water,  and 
the  resulting  lye  poured  into  a  narrow  cylinder  which  is  then  to  be  care- 
fully closed.  After  the  oxyd  of  copper  has  completely  settled,  the  super- 
natant liquid  may  be  drawn  off  with  a  syphon.  It  contains  no  traces  of 
copper.  The  solution  is  best  preserved  free  from  carbonic  acid  by  Mohr's 
method,  namely  by  closing  the  bottle  with  a  cork  through  which  passes  air- 
tight a  tube  open  at  both  ends,  and  filled  with  a  coarse  mixture  of  Glauber 
salt  and  caustic  lime.  Iron  decomposes  saltpetre  as  completely  as  copper, 
but  it  cannot  be  employed  to  prepare  pure  potash  in  consequence  of  its 
containing  carbon,  silicon,  phosphorus,  &c.  When  the  above  propor- 
tions of  copper  and  saltpetre  are  used,  a  portion  of  the  copper  is  obtained 
in  the  form  of  suboxyd.  For  a  second  operation  we  may  take  1  part  of 
nitre,  1  of  this  oxyd,  and  1  of  metallic  copper.  After  complete  washing, 
the  oxyd  of  copper  may  be  dissolved  in  sulphuric  acid,  and  thus  converted 
into  blue  vitriol. — Annalen  der  Chemie  und  Pharmacie,  lxxxvii.  373. — 
£This  process  will  be  particularly  convenient  if,  as  appears  probable,  the 
resulting  oxyd  of  copper  is  in  a  proper  condition  to  be  used  in  organic 
analysis.  If  not,  it  might  be  reduced  at  a  low  red  heat  by  coal  gas.  and 
again  employed  to  decompose  nitre. — w.  c] — Silliman's  Journal,  Jan.  1854. 
On  the  Polarization  of  light  by  refraction  through  a  metal. — Biot  found  that 
two  gold  leaves  are  sufficient  to  polarize  direct  solar  rays  completely.  Roll- 
mann  has  examined  the  subject  anew,  and  has  employed  the  gold  leaves 
both  as  a  polarizing  and  as  an  analyzing  arrangement.  When  the  light  is 
very  intense,  only  a  single  leaf  can  be  employed,  as  otherwise  the  field  of 
view  appears  too  dark.  When  used  as  an  analyzer,  a  gold  leaf  shows  very 
distinctly  the  colors  of  thin  plates  of  gypsum,  cooled  glasses,  &c,  but  these 
are  naturally  modified  by  the  peculiar  blue  green  color  of  the  gold.  If  we 
allow  plane  polarized  light  to  pass  through  an  inclined  gold  leaf,  and  ex- 
amine by  a  tourmaline  in  the  light  so  transmitted  a  plate  of  calospar  cut 
