ON  THE  PREPARATION  OF  CHLOROFORM.  43 
to  bent  the  mixture  to  a  certain  degree.  The  slower  it  is  heated, 
the  lower  ought  the  temperature  to  be ;  when  heated  rapidly,  it 
may  become  a  few  degrees  hotter  without  any  disadvantage. 
After  the  removal  of  the  fire,  the  temperature  usually  sinks  to 
102  or  104°  F.,  remains  stationary  for  about  half  an  hour,  and 
then  commences  to  rise  again  :  this  rise  of  temperature  is  higher, 
the  less  and  the  slower  it  had  previously  decreased.  The  highest 
degree  attained  in  about  96  operations  between  62  and  74°  R. 
(171.5  and  198.5°  F.)  If  the  thermometer  has  fallen  to  below 
30°  R.  (100°  F.)  the  reaction  will  not  commence  for  several 
hours,  and  it  is  preferable  to  heat  the  mixture  a  few  degrees 
higher. 
When  the  temperature  has  risen  to  122°  F.,  chloroform  be- 
gins to  pass  over,  and  with  the  constant  and  rapid  rise  of  the 
thermometer,  the  distillate  soon  runs  in  a  continuous  stream. 
After  the  highest  heat  has  been  reached,  the  last  portions  of 
chloroform  are  carefully  distilled  by  a  moderate  heat,  and  finally 
the  remainder  of  the  alcohol,  which  is  detained  by  the  chloride 
of  calcium  with  a  certain  force  so  that  the  theremometer  reaches 
213  to  214°  F.,  before  the  last  portions  are  expelled.  If  now 
a  second  distillation  is  undertaken,  the  fire  ought  to  be  slower 
than  with  the  first  one,  because  the  still  and  its  surroundings  are 
still  warm.  The  weak  spirit  obtained  by  distillation,  and  by 
washing  the  chloroform,  is,  after  ascertaining  its  strength,  used 
for  the  second  operation.  An  increase  of  the  alcohol  over  17 \ 
per  ct.  was  never  accompanied  with  an  increase  of  the  yield  ; 
indeed,  100  lb.  chloride  of  lime,  containing  30  per  ct.  active 
chlorine,  require  of  the  above  alcohol  but  3.178  lb.,  according 
to  the  following  formula  :  2(C4H602)+8  (Ca  Cl-fCa  0,+C10)  = 
C2HC]8+3(CaO+C2H03)+13CaCl+8HO.  Practically,  5j 
to  61b.  alcohol  were  used,  but  the  author  recommends  not  to 
decrease  the  quantity  below  15  or  17  J  per  ct.  as  it  is  preferable 
to  have  some  alcohol  in  excess,  than  to  lose  chlorine  uncom- 
bined. 
The  chloroform  obtained  as  above,  is  freed  from  the  spirituous 
portion,  by  a  separating  funnel  and  now  contains  chiefly  some 
alcohol  as  impurity,  which  is  removed  by  repeated  washing  with 
water  ;  when  agitated  with  an  equal  volume,  its  first  loss  is  about 
15,  the  second  time  6  or  7,  the  third  time  about  3  per  ct.  by 
