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SPECIFIC  GRAVITY  OF  MEDICINAL  CHLOROFORM.  73 
record  kept  of  44  carboys,  with  the  specific  gravity  taken  by  the 
one-thousand-grain  bottle,  shows  that  18  came  fully  up  to  the 
Pharmacopoeia,  ranging  between  1-4901  and  1-4933.  The  other 
26  were  mostly  only  an  insignificant  fraction  below  the  former, 
while  several  carboys  were  as  low  as  1*4841,  1-4844,  1*4846, 
1-4860,  &c.  These  variations  are  easily  accounted  for,  if  it  is 
borne  in  mind  that  the  preparation  was  made  on  a  very  extensive 
cale,sand  that  in  practice  the  specific  gravity  is'taken  with  a  hy- 
drometer; then  the  result  will  be  easily  affected  by  a  reduction  of 
the  temperature  caused  by  the  rapid  evaporation  of  the  chloro- 
form, thus  making  the  latter  appear  heavier  than  it  in  reality  is. 
It  was  observed  that  this  chloroform  decomposed  much  more 
rapidly  than  that  of  other  manufacturers,  and  it  was  determined 
to  ascertain  the  cause  of  it. 
In  the  first  place,  pure  chloroform,  which  had  been  furnished 
to  the  medical  department  of  the  army,  was  procured.  Of  four- 
teen samples,  eleven  were  below  1*480,  the  lowest  being  1*4760, 
the  highest  weighed  1*4806,  1*4815  and  1*4837.  On  exposing 
these  and  some  made  at  the  Laboratory  to  the  direct  sunlight, 
the  latter  was  decidedly  acid  in  the  course  of  a  day,  while  the 
former  withstood  the  action  of  the  light  for  two  or  three  days, 
and  its  decomposition  did  not  proceed  quite  as  fast  as  in 
the  other  case. 
A  portion  of  the  heavy  chloroform  was  reduced  by  the  addi- 
tion of  a  little  strong  alcohol,  when  it  withstood  the  decompos- 
ing influence  of  light  quite  as  well  as  the  samples  referred  to. 
Some  of  these  latter  were  now  rectified,  in  order  to  obtain 
them  of  the  standard  gravity  of  the  Pharmacopoeia.  Sulphuric 
acid  was  carefully  avoided,  because  it  has  been  asserted  by  some 
that  it  makes  chloroform  prone  to  decomposition.  By  one 
simple  rectification  from  a  water  bath,  the  gravity  of  chloroform 
is  not  much  increased.  But,  if  previously  washed  with  water, 
and  rectified  over  chloride  of  calcium  in  a  water  bath,  it  may  be 
obtained  of  the  full  strength  required  by  the  Pharmacopoeia. 
If  this  chloroform  was  exposed  to  the  light  alongside  of  that 
prepared  at  the  place,  no  difference  could  bo  observed  in  their 
behaviour,  both  being  decidedly  acid  after  one  day's  exposure. 
It  was  next  thought  that  probably  the  impurities  contained  in 
