WOOD  SPIRIT  AND  ITS  DETECTION. 
153 
Society  is  to  bring  forward  a  new  and  reliable  test  for  the  detect- 
ion of  pyro^ylic  spirit,  and  likewise  to  give  a  brief  preliminary 
notice  of  some  experimental  results  which  I  have  obtained  in 
the  course  of  an  investigation  undertaken  with  a  view  to  the 
complete  separation  of  the  more  volatile  constituents  of  wood 
naphtha. 
As  pyroxylic  spirit  in  its  purest  commercial  form  has  been 
the  subject  of  most  of  my  experiments,  it  may  be  interesting  to 
describe  briefly  the  process  by  which  it  is  manufactured  on  the 
large  scale. 
When  wood  is  distilled  in  close  vessels,  and  at  high  tempera- 
ture, it  yields  a  variety  of  products,  which  may  be  classed 
under  three  heads — solid,  liquid,  and  gaseous.  The  solid  and 
gaseous  products,  not  being  connected  with  our  present  subject, 
may  be  dismissed  without  further  comment,  our  attention  being 
solely  confined  to  the  liquid  portions.  The  tarry  mixture  which 
is  the  result  of  the  first  operation  is  rectified,  and  the  more 
volatile  portions  redistilled  from  lime  or  chalk,  by  which  means 
the  acetic  acid,  which  is  present  in  large  quantity  in  the  crude 
liquor,  is  got  rid  of.  The  distillate  then  constitutes  the  rough 
wood-naphtha  of  commerce.  When  required  for  medicinal  use, 
this  is  further  purified  as  follows  ; — The  crude  material  is 
largely  diluted  with  water,  by  which  means  the  oily  hydrocar- 
bons always  present  are  precipitated,  the  last  trace  of  these 
being  afterwards  removed  by  the  action  of  oxidizing  agents. 
The  ^ery  weak  methylic  spirit  thus  produced  is  then  frequently 
rectified  per  se,  and  finally  over  quick-lime  until  the  specific 
gravity  is  reduced  to  about  800.  It  then  constitutes  medicinal 
naphtha. 
The  spirituous  liquid  thus  produced  is  far  from  pure,  since 
it  consists  of  a  mixture  of  acetate  methyl,  of  acetone, 
methylic  alcohol,  and  other  bodies,  which  have  been  as  yet  but 
very  imperfectly  examined.  Were  we  to  attempt  to  separate 
these  impurities  by  fractional  distillation  alone,  failure  could 
only  attend  our  efforts,  as  a  comparison  of  the  boiling  points  of 
the  three  bodies  already  mentioned  will  show. 
Acetate  of  methyl  boils  at  133°  F. 
Acetone        «  '      "        133°  F. 
Methylic  alcohol      «       149*  F. 
