^"-jiZ^s^s"""'}  Laboratory  Notes,  33 
this  in  no  way  except  in  the  quantity  of  Hme  employed  ;  using  the 
smallest  quantity  of  lime  necessary  to  abstract  all  the  water,  it  is  sur- 
prising how  complete  the  lime  will  perform  its  function  in  this  respect. 
Take,  for  instance,  one  litre  of  alcohol  of  94  per  cent,  j  this  contains 
about  60  grams  of  water;  if  to  this  be  added  120  grams  of  good 
and  fresh  burnt  lime,  requiring  about  40  grams  of  water  to  convert 
it  into  hydrate,  actual  experiment  proves  that,  when  kept  in  contact  with 
the  alcohol  a  sufficient  length  of  time,  it  accomplishes  this  absorption  of 
water,  and  the  alcohol  decanted  from  the  precipitated  lime  will  be  fully 
98  per  cent. 
Operating  upon  this  fact,  I  have  been  long  in  the  habit  of  supplying 
myself  with  alcohol  of  98  and  100  per  cent.,  by  proceeding  in  the  fol- 
lowing manner  :  I  have  in  my  laboratory  three  or  four  two-litre  bottles, 
into  each  of  which  I  place  i|  litre  of  94  per  cent,  alcohol,  the  strongest 
alcohol  sold  in  commerce  ;  to  this  is  added  180  grams  of  fresh  burnt 
lime  of  the  best  quality  broken  up  into  a  coarse  powder.  These  bottles 
are  set  aside  on  the  shelf  and  agitated  from  time  to  time,  the  oftener 
this  is  done  the  more  rapid  will  the  reaction  be  accomplished.  A  week 
or  ten  days  will  usually  suffice,  when  the  bottles  are  allowed  to  remain 
at  rest,  and  the  hydrate  of  lime  will  settle  in  a  few  days,  and  by  a  siphon 
two-thirds  of  the  original  alcohol  can  be  drawn  off  free  from  lime,  which 
marks  98  per  cent,  alcohol,  and  when  filtered,  and  50  c.c.m.  evaporated 
to  dryness  there  will  be  left  only  the  merest  trace  of  lime,  less  than  one- 
half  milligramme.  But,  of  course,  redistillation  is  so  simple  that  if  we 
wish  the  alcohol  at  98°  it  can  be  readily  distilled  over  a  water-bath. 
The  magma  remainmg  in  the  bottle,  when  distilled  over  a  water-bath, 
furnishes  the  remainder  of  the  alcohol  about  one-half  per  cent,  higher. 
When  absolute  alcohol  is  desired,  take  the  alcohol  just  as  it  has  been 
siphoned  off  or  distilled  from  the  magma,  put  it  into  a  convenient  flask 
for  distillation,  and  to  each  litre  add  120  grams  of  lime  in  coarse 
powder,  attach  to  a  Liebig  condenser  inverted,  so  that  the  alcohol  will 
run  back  into  the  flask  when  condensed  ;  this  is  continued  for  an  hour 
and  a  half  or  two  hours.  The  condenser  is  then  placed  in  its  normal 
condition  and  alcohol  distilled  over  which  will  mark  100  per  cent. 
Recently  I  have  learned  that  there  is  a  method  adopted  of  making  the 
absolute  alcohol  by  one  distillation,  operating  by  the  inverted  condenser 
first,  but  in  this  process  the  amount  of  lime  called  for  is  the  usual  quan- 
tity, whereas  I  find  that  by  reducing  the  lime  to  its  minimum,  and 
always  having  bottles  ready  to  furnish  98  per  cent,  alcohol,  the  oper- 
3 
