Am.  Jour.  Phariu.  "| 
May,  1882  j" 
Chemical  Notes. 
217 
weight  of  the  first  crystallization  amounted  in  one  experiment  to  44 
per  cent,  of  the  pure  grape  sugar  used,  which  would  correspond  to  27 
per  cent,  of  pure  lactic  acid. 
In  a  second  paper,  Kiliani  gives  fuller  results  and  still  more  satis- 
factory directions  for  the  preparation  of  lactic  acid.  He  here  states 
that  the  best  material  for  the  preparation  of  lactic  acid  is  invert  sugar, 
as  it  gives  a  better  yield  than  ordinary  glucose ;  and  that  caustic  soda 
is  to  be  preferred  strongly  to  caustic  potash.  Besides  its  greater 
cheapness  he  finds  that  the  sodium  sulphate  formed  on  neutralizing 
takes  up  the  greater  part  of  the  water  present,  combining  with  it  as 
water  of  crystallization.  The  presence  of  sulphate  in  the  alcoholic 
solution  can,  with  proper  manipulation,  and  without  the  use  of  too 
much  alcohol,  be  reduced  to  a  minimum.  It  is  not  advantageous 
to  neutralize  the  entire  alcoholic  solution  with  zinc  carbonate,  as  the 
zinc  salt  of  another  acid  that  is  produced  at  the  same  time  as  the 
lactic  acid  does  not  crystallize  and  interfere  with  the  crystallization 
of  the  zinc  lactate.  The  procedure  now  recommended  by  Kiliani  is 
as  follows :  500  grams  of  cane  sugar  are  placed,  with  250  grams  of 
water  and  10  cb.  cm.  of  the  sulphuric  acid  to  be  used  later,  in  a  stop- 
pered flask  of  2  liters  capacity,  and  heated  for  3  hours  to  about  50  °C. 
The  solution  of  invert  sugar  so  obtained  is  colorless,  or  at  most  faintly 
yellow.  After  cooling,  there  is  added  to  it,  in  portions  of  50  cb.  cm. 
at  a  time,  400  cb.  cm.  of  a  caustic  soda  solution  made  by  dissolving 
1  part  of  caustic  soda  in  1  part  of  water.  The  strong  alkali  settles  at 
first  as  a  slimy  mass  on  the  bottom,  and  a  new  portion  is  only  to  be 
added  when  the  mixture  has  become  perfectly  homogeneous  by  shak- 
ing around.  The  flask  should  also  be  cooled  with  water  while  the 
alkali  is  being  added.  The  mixture,  nevertheless,  takes  color  and 
becomes  greatly  heated.  Finally,  the  mixture  is  heated  to  60°  to 
70°C.,  until  a  test  heated  over  a  boiling  water-bath  does  not  separate 
cuprous  oxide  from  Fehling's  solution,  but  gives  it  only  a  slight  green- 
ish tinge.  Into  the  cooled  mixture  the  calculated  amount  of  sulphu- 
ric acid  (made  by  mixing  3  parts  of  sulphuric  acid  with  4  of  water) 
is  then  run.  As  soon  as  the  acid  liquid  has  cooled  to  the  temperature 
of  the  room  drop  in  a  crystal  of  Glauber^s  salt,  and  dip  the  flask  in 
cold  water  until  a  thin  crystalline  crust  forms  on  the  sides,  which  is 
then  removed  by  rapid  shaking  about  of  the  flask.  Cooling  and  shak- 
ing are  continued  until  a  crust  no  longer  forms,  Avhen  the  mixture  is 
allowed  to  stand  (piiet  for  12  to  24  hours.    At  the  end  of  this  time 
