PREPARATION  OF  HEAVY  OIL  OF  WINE. 
101 
alcohol,  whereby  the  formation  of  oil  of  wine  is  entirely  pre- 
vented. The  conclusion  must,  therefore,  be  arrived  at,  that  the 
absence  of  water,  the  generation  of  sulphurous,  and  the  forma- 
tion of  thiomelanic  acid,  are  requisite  to  the  formation  of  the 
heavy  oil  of  wine. 
On  heating  a  mixture  of  sulphuric  acid  and  alcohol,  sulpho- 
vinic  acid  is  formed.  By  heating  sulphuric  acid  to  150°  C. 
(302°  F.,)  and  dropping  nearly  concentrated  sulphovinic  acid 
upon  it,  a  black  mass,  undoubtedly  thiomelanic  acid,  and  heavy 
oil  of  wine,  are  separated,  while  sulphurous  acid  is  given  off. 
This  observation  of  Dunos  gives  the  lowest  temperature  as  yet 
noticed  in  the  formation  of  heavy  oil  of  wine,  and  it  agrees 
pretty  well  with  the  observations  of  Mr.  C.  Lewis  Diehl,  Jr., 
made  at  the  U.  S.  Army  Laboratory  at  Philadelphia,  and  which 
are  published  in  the  Proceedings  of  the  American  Pharmaceuti- 
cal Association  for  1864,  p.  309.    [See  p.  126  of  this  number.] 
A  slight  error  has  crept  into  that  paper,  which,  though  it 
scarcely  affects  the  results,  and  has  no  influence  on  his  de- 
ductions, needs  correction.  Towards  the  close  of  his  paper, 
Mr.  Diehl  states  that  the  amount  of  alcohol,  spec.  grav.  *809, 
consumed,  was  367|  gallons.  The  alcohol  used  was  commercial 
95  per  cent,  alcohol,  which  has  generally  a  specific  gravity  of 
817,-but  is  occasionally  as  low  as  '815.  One  gallon  of  alcohol, 
spec.  grav.  *817,  weighs  6'808  lbs. ;  the  amount  consumed  by 
Mr.  Diehl  weighed,  therefore,  2503-64  lbs. ;  the  yield  of  oil  was 
558 J  oz.,  or  one  ounce  avoird.  for  71*77  ounces  avoird.  of  the 
alcohol. 
Since  the  paper  above  alluded  to  was  written,  Mr.  Diehl  has 
made  another  series  of  distillations,  the  results  of  which,  at  my 
request,  he  has  put  into  tabular  form,  which  I  herewith  pre- 
sent. The  great  care  taken  in  noting  down  his  observations  is 
very  commendable,  and  it  will  be  seen  at  a  glance  that,  practi- 
cally, these  numerous  figures  are  more  valuable  than  pages  of 
theoretical  reasoning. 
In  explanation  of  the  table,  it  is  only  necessary  to  state  that 
the  columns  1st,  2d,  &c.  heating,  contain  the  highest  tempera- 
ture to  which  the  mixture  rose,  and  the  lowest  to  which  it  fell 
before  it  was  re-heated. 
( 
