132 
ON  THE  MANUFACTURE  OF  OLEUM  JETHEREUM. 
bubbles  thrown  up  during  the  earlier  period  of  the  distillation 
were  very  small,  the  liquid  was  very  apt  to  froth ;  if,  on  the 
contrary,  the  bubbles  were  large,  this  seldom  happened,  and, 
in  fact,  in  the  only  cases  where  it  did  so,  the  cause  could  be 
traced  to  high  heating.  It  is  well,  therefore,  to  watch  the  re- 
torts very  closely,  and  to  manage  the  fires  carefully  when  the 
boiling  takes  place  in  small  bubbles.  The  temperature  should, 
however,  in  no  case  be  allowed  to  fall  below  300°,  even  if  it  is 
at  the  risk  of  frothing,  for  very  good  yields  have  been  obtained 
where  frothing  occurred. 
The  distillate  obtained  generally  consisted  of  two  layers ;  the 
heavier  containing  water  saturated  with  sulphurous  acid,  the 
lighter  consisting  of  an  ethereal  solution  of  oil  of  wine.  Oc- 
casionally, however,  the  positions  were  reversed,  the  solution 
of  oil  of  wine  taking  the  lower  stratum,  while  the  watery 
liquid  occupied  the  upper ;  and  several  instances  have  occurred 
when  three  layers  were  formed,  the  upper  and  lower  consist- 
ing of  solution  of  oil  of  wine,  while  the  centre  was  occupied  by 
the  watery  liquid.  The  oil  of  wine  was  separated  from  its 
solution  by  exposure  to  a  dry  current  of  air  for  from  twelve  to 
twenty -four  hours.  The  liquid  was  then  found  to  have  sepa- 
rated again  into  two  layers,  and  was  mixed  with  about  three 
times  its  volume  of  distilled  water,  transferred  to  a  separatory 
funnel  and  allowed  to  remain  at  rest  for  several  hours.  The 
oil  was  then  drawn  off  and  the  process  of  washing  repeated 
until  it  no  longer  affected  litmus. 
Oil  of  wine,  as  thus  obtained,  is  a  limpid,  oily  liquid,  of  a 
pale  straw  color,  having  a  pungent  and  aromatic  taste,  and  an 
odor  reminding  of  the  artificial  fruit  essences.  No  very  ac- 
curate examinations  as  to  specific  gravity  were  made.  In 
three  cases  noted,  they  were  respectively  1*065,  1*095,  1*100, 
and,  as  far  as  recollected  in  a  number  of  other  cases,  they 
ranged  between  1*080  and  1*100. 
On  the  basis  of  the  foregoing  observations,  it  may  be  conve- 
nient to  state,  in  a  more  condensed  form,  the  precautions  neces- 
sary in  the  distillation  of  heavy  oil  of  wine. 
u  The  retort  should  be  set  in  a  sand  bath  with  but  a  thin 
