VARIETIES. 
375 
iodine  at  a  temperature  of  50°-59°  F.  at  the  outside,  so  that  it  may  have  a 
golden-yellow  color  with  no  trace  of  reddish-orange. 
The  biting  is  commenced  by  covering  the  plate  with  iodized  water,  which 
is  renewed  in  ten  minutes  or  a  quarter  of  an  hour  ;  a  part  has  then  combined 
with  the  steel  to  form  iodide  of  iron,  and  the  other  is  volatilized,  so  that  it  is 
important  to  change  the  iodized  water  two  or  three  times,  that  is  to  say, 
until  the  plate  is  considered  to  be  sufficiently  bitten. 
The  biting  takes  place  slowly,  and  is  never  deep  enough,  unless  the  ope- 
ration is  completed  by  water  slightly  acidulated  with  nitric  acid  ;  it  has 
then  sufficient  action  to  eat  into  the  metal  to  a  greater  depth  than  the 
iodine,  without,  however,  attacking  the  ground.  The  application  of  this 
method  has  given  excellent  results. — London  Chem.  Gaz.from  Comptes  Ren- 
Ms,  March  12,  1855,  p.  584. 
Upon  some  Oils  of  the  Dolphin  and  Phocenic  Acid. — By  M.  Bertheolot. 
— Since  the  discovery  of  valerianic  acid,  it  has  been  supposed  that  the  vola- 
tile oils  of  the  fat  of  the  dolphin,  to  which  Chevreul  first  gave  the  name  of 
phocenic  acid,  is  valerianic  acid.  Probable  as  this  identity  appeared,  how- 
ever, it  was  doubted  by  some  chemists.  But  Heintz's  work  upon  the  fats 
must  especially  be  regarded  as  contradicting  this  identity,  as  Heintz  found 
that  the  neutral  fats  of  the  animal  kingdom  only  contained  numbers  of  atoms 
of  carbon  divisible  by  four.  Bertheolot  has  therefore  examined  the  fat  of  seve- 
ral dolphins,  and  amongst  others  that  of  Delphinus  Marginatus,  Cuv.,  and 
also  that  of  some  sharks,  such  as  Mustellus  vulgarus,  Cuv.,  and  Scymnusni- 
ceensis,  Cuv.,  and  always  found  that  the  volatile  acid  was  valerianic  acid. 
To  ascertain  the  presence  of  volatile  acids  in  fat,  Bertheolot  distils,  at  a 
gentle  heat  100  grms.  of  the  fat  with  100  grms.  of  a  mixture  of  alcohol  and 
sulphuric  acid.  If  the  first  portion  of  the  distillate  be  mixed  with  water, 
the  ethers  of  the  volatile  acids  separate. 
The  author  afterwards  prepared  valerianic  acid  in  the  ordinary  manner, 
and  analysed  it  and  its  ether.  The  results  obtained  were  distinctly  in  fa- 
vor of  the  identity  of  the  so-called  phocenic  acid  with  valerianic  acid. — 
Ibid,  from  Journ.  de  Pharm  et  de  Chim.,  3  ser.,  xxvii.  p  35. 
Tasteless  Infusion  of  Senna. — Dr.  Brandeis  recommends  a  cold  infusion 
of  senna  for  twelve  hours  in  a  covered  vessel,  as  especially  useful  in  infan- 
tile therapeutics.  By  this  modification  of  the  process  usually  employed, 
the  water  contains  only  the  cathartic  and  the  coloring  matter,  leaving  the 
essential  oil,  the  fatty  matter,  and  the  irritating  resin,  which  are  only  solu- 
ble in  hot  water.  Senna  water  thus  prepared  cold,  is  almost  insipid,  and 
its  taste  completely  disappears  when  mixed  with  infusion  of  coffee  or  tea. 
— Boston  Med.  and  Surg.  Journ.  from  Archives  Generales  de  Med.  for  April. 
Limits  of  the  vaporization  of  Mercury. — Till  now  it  has  been  admitted 
with  Faraday  that  the  vaporization  of  mercury  is  very  limited ;  that  at  20°' 
