296 
ON  CHLOROFORM. 
off  a  charge  was  from  three  and  a  half  to  four  hours,  so  that  by 
good  management  and  hard  work  three  charges  could  be  worked 
up  in  a  day's  work  of  eleven  hours  (counting  the  dinner  hour), 
making  about  150  lb  washed  chloroform  the  average  product  of 
a  day.  The  amount  of  chlorinated  lime  actually  used  for  each 
charge  was  equivalent  to  about  200  ib  of  active  chlorine,  or  little 
exceeding  that  figure.  The  first  charge  distilled  in  the  morning 
required  a  longer  time  than  subsequent  ones,  because  the  whole 
apparatus  was  heated,  and  we  started  then  with  the  temperature 
from  12  to  18°  F.  higher  than  early  in  the  morning. 
The  process  of  purification  is  based  essentially  upon  the  same 
principles  as  that  of  our  Pharmacopoeia,  though  the  manipulation 
was  varied  to  better  enable  us  for  an  uninterrupted  continuance 
of  purification,  and  to  avoid  as  much  as  possible  loss  of  material. 
The  statement  of  Hirsch,*  that  washed  crude  chloroform  can  be 
obtained  perfectly  pure  without  previous  treatment  with  sul- 
phuric acid,  simply  by  rectification  at  a  temperature  not  exceed- 
ing 158°  F.,  was  repeatedly  verified  by  experiments  on  a  large 
scale  (about  16  gallons  at  a  time)  ;  but  the  trouble  attending  the 
limitation  of  temperature,  in  consequence  of  the  occasional 
change  in  the  pressure  of  steam,  and  the  evaporation  of  the 
water  from  the  bath,  required  the  constant  attendance  of  a  la- 
borer, so  that  it  was  found  practicable  to  change  the  process  to 
one  which  required  only  occasional  attention. 
After  the  chloroform  had  been  purified  by  agitation  with  sul- 
phuric acid  and  carbonate  of  soda,  and  properly  diluted  with  al- 
cohol, it  was  at  first  rectified  in  this  condition  ;  subsequently, 
however,  the  addition  of  some  caustic  lime  into  the  rectifier  was 
'found  advantageous.  The  distillate  was  collected  in  one-half  or 
one  gallon  bottles,  and  the  contents  of  each  bottle  tested  by  sul- 
phuric acid  to  ascertain  its  purity.  The  last  portions  from  the 
rectifying  still  always  imparted  more  or  less  color  to  sulphuric 
acid  and  were  returned  to  the  sulphuric  acid  washer. 
The  rectified  chloroform  was  kept  surrounded  by  water  in  a 
copper  tank,  from  which  it  was  drawn  by  measuring  cocks  dis- 
charging respectively  one-half  and  one  pound  of  chloroform,  sp. 
*  Amer.  Journ.  Pharm.  1862,  44. 
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