84 
VALERIANIC  ACID. 
tion  of  the  distillate,  after  being  treated  with  sulphuric  acid  in 
the  same  manner  as  the  first,  may  be  returned  to  the  retort  after 
the  first  is  all  distilled  ofi",  and  the  distillation  repeated  as  before. 
In  using  the  sulphuric  acid  for  dehydration,  it  is  best  to  have 
the  valerianic  acid  in  a  tall  narrow  glass  cylinder  or  hydrometer 
jar,  then  add  the  sulphuric  acid  gradually  drop  by  drop,  so  long 
as  it  dofes  not  dissolve  in  the  valerianic  acid,  care  being  taken 
not  to  shake  or  agitate  the  vessel  during  the  process.  The 
sulphuric  acid,  as  it  drops  into  the  valerianic  acid,  breaks  into 
little  globules  and  falls  like  fine  rain  or  mist  to  the  bottom.  A 
point  is,  however,  reached  when  the  two  acids  unite,  and  tliis  is 
the  limit.  After  standing  a  few  moments,  much  of  the  partially 
dehydrated  acid  can  be  poured  ofi"  into  the  retort  for  distillation, 
and  the  remainder  may  be  separated  by  means  a  separating 
funnel.  In  manipulating  with  varying  proportions  of  sulphuric 
acid  for  the  dehydration,  the  best  proportions  appeared  to  be 
about  360  grains  of  the  officinal  sulphuric  acid,  and  this  was 
applied  to  about  6J  fluidounces  of  the  valerianic  acid  (s.  g. 
0*958)  to  be  dehydrated,  or  the  average  quantity  obtained  by 
the  officinal  formula.  The  writer,  however,  found  it  more  con- 
venient to  use  four  times  the  quantity  of  the  officinal  formula, 
and  upon  such  proportions  are  his  general  results  based.  In  the 
last  experiment  made  with  four  times  the  officinal  quantity,  great 
care  was  taken  to  observe  the  boiling  point  of  the  acid,  and  its 
specific  gravity  at  the  various  temperatures  during  the  distilla- 
tion ;  each  fluidounce,  as  it  dropped  from  the  condenser,  was  set 
aside,  the  specific  gravity  taken  and  the  temperature  at  which  it 
came  over  noted.  From  the  table  given  below  it  will  be  seen, 
that  only  three  fluidounces  out  of  twenty-four  were  obtained  of 
a  s.  g.  0-933,  ten  fluidounces  had  a  s.  g.  0-9355,  which,  when 
mixed  with  the  three  fluidounces  of  s.  g.  0-933,  made  thirteen 
fluidounces  of  s.  g.  0-935.  The  first  nine  fluidounces  that  came 
over  were  set  aside,  again  treated  with  sulphuric  acid  until  its 
specific  gravity  was  reduced  to  0*945,  returned  to  the  retort,  re- 
distilled, and  by  still  another  fractional  treatment  with  sulphuric 
acid  and  distillation  six  fluidounces  more  of  valerianic  acid  of 
the  s.  g.  0-935  were  obtained  from  it,  making  nineteen  fluid- 
ounces  in  all,  or  a  loss  of  five  fluidounces  in  the  process.  The 
