■^™Mai"^883*'™  }        Turpentine:  its  Nature  and  Adulterations.  147 
were  written  at  the  request  of  Mr.. Charles  Rice,  American  editor  of  the 
Pharmacographia 
"  Turpentine  is  distilled  in  coi)per  stills  now.  Formerly  iron  stills  were 
used.  All  crude  tarpentine  is  distilled  with  water.  A  fifteen-barrel  still 
(barrel  weighs  two  hundred  and  eighty  pounds)  is  charged  early  in  the 
morning.  Gentle  heat  is  first  applied  until  the  mass  is  liquefied,  and  a 
■coarse  wire  skimmer  is  used  to  remove  the  chips,  bark,  leaves,  and  such 
other  foreign  substances  as  rise  to  the  surface,  the  temperature  meanwhile 
rising  until  316°  F.  is  reached.  All  the  accidental  water  (that  contained  in 
the  crude  turpentine  as  it  comes  from  the  forest)  having  been  distilled  offj 
a  small  stream  of  cold  water  is  now  let  in,  so  that  the  heat  is  kept  at  or 
below  316°  F.,  the  boiling  point  of  oil  of  turpentine.  The  oil  of  turpentine 
and  water  now  come  over,  and  the  mixture  is  caught  in  a  wooden  tub. 
The  distiller  tests  the  quality  of  the  flow  from  time  to  time  in  a  proof-glass, 
.and  the  distillation  is  continued  until  the  proportion  of  water  coming  over 
is  9  of  water  to  1  of  oil  of  turpentine.  At  this  stage  the  heat  is  withdrawn, 
the  still-cap  is  taken  off,  and  the  hot  resin  is  drawn  off  by  a  valvular  cock 
at  the  side  of  the  still  near  the  bottom.  This  resin  passes  through  a  strainer 
before  it  reaches  the  vat,  to  rid  it  of  foreign  substances,  which  may  not  have 
been  previously  removed  by  the  skimmer.  The  yield  of  oil  of  turpentine 
from  'virgin  dip'  (the  first  exudation  from  a  newly-boxed  tree)  is  about 
6  gallons  to  the  barrel,  about  20  per  cent,  being  left  in  the  resin, ^  since  the 
removal  of  a  larger  proportion  would  darken  the  color,  and  consequently 
depreciate  its  value.  The  yield  from  'yellow  dip'  (the  runnings  of  the 
second  and  subsequent  years)  is  about  4  gallons  to  a  barrel.  The  yield  from 
'scrapings'  (the  inspissated  gum  from  the  tree  facings)  is  about  2  to  S} 
gallons,  according  to  age,  and  also  to  the  proportion  of  trash  which  it 
contains." 
The  separation  of  turpentine,  by  what  is  j)ractically  a  steam  distillation 
process,  serves  to  explain  the  fact  which,  until  I  received  the  above  infor- 
mation, had  often  surprised  me,  that  the  commercial  article  is  uniformly 
free  from  products  of  the  decomposition  of  resin  by  heat. 
Some  idea  of  the  importance  of  the  turpentine  industry  will  be  gathered 
by  inspection  of  the  following  table,  representing  the  number  of  barrels 
imported  into  London  since  1872  : 
1873   44,495  1878   56,221 
1874   57,720  1879   42,960 
1875   57,093  1880   39,649 
1876   57,371  '  1881   63,724 
1877   49,500  1882   57,489 
Probably  about  two-thirds  of  the  entire  quantity  sent  to  this  country  is 
landed  in  London. 
In  so  far  as  general  properties  are  concerned,  there  is  no  practically  dis- 
tinguishable difference,  other  than  in  color,  I  believe,  between  various 
samples  of  the  commercial  article,  but  tested  by  the  polari meter  they  vary 
considerably. 
iThe  fact  that  the  whole  of  the  hydrocarbon  is  not  removed  accounts  for  the  state- 
ment sometimes  made,  that  "resin  spirit"  is  optically  active,  that  made  from  pure 
a-esin,  according  to  my  experiments,  being  inactive. 
