MEETING  OF  THE  BRITISH  ASSOCIATION. 
483 
that  element.  The  chief  interest  attached  to  this  new  applica- 
tion is  the  utilization  of  a  waste  disagreeable  product  which 
otherwise  would  be  a  nuisance. 
3.  In  making  bleaching  powder  or  chlorinated  lime,  chloride 
of  chromium  has  been  to  a  considerable  extent  substituted,  as 
the  source  of  chlorine,  for  the  black  oxide  of  manganese  and 
common  salt. 
4.  The  aluminous  shale,  found  in  contact  with  coal  strata,  is 
now  very  much  used  in  South  Lancashire  in  the  manufacture  of 
alum.  The  shale  is  calcined  to  destroy  the  bituminous  and 
coloring  matter,  and  then  treated  with  sulphuric  acid  and  the 
ammoniacal  liquor  of  gas  works  simultaneously ;  as  it  is  not 
necessary  first  to  form  the  sulphate  of  alumina  and  then  to  add 
the  ammoniacal  liquor,  if  care  be  taken  that  the  mixture,  when 
added,  should  have  a  decided  excess  of  acid.  As  much  as  110 
tons  a  week  are  now  made  by  this  process,  equal,  the  reporter 
said,  to  more  than  one-third  of  the  whole  of  the  alum  made  in 
England. 
5.  Sawdust  has  to  a  great  extent  been  substituted  for  pieces 
of  wood,  in  the  manufacture  of  pyroligneous  acid,  on  economical 
grounds. 
6.  A  new  process  for  oxalic  acid  has  almost  entirely  super- 
seded the  old  one  of  acting  on  sugar  or  starch  by  nitric  acid. 
It  is  based  on  the  fact  that  this  acid  results,  in  large  quantities, 
from  the  reaction  between  caustic  alkalies  and  certain  organic 
substances.  The  substance  chosen  is  sawdust,  which  is  treated 
by  a  mixture  of  two  equivalents  of  soda  and  one  of  potassa.  It 
has  been  found  that  a  mixture  of  the  two  alkalies  is  essential  to 
the  proper  working  of  the  process ;  but  the  reporter  did  not 
seem  to  understand  precisely  why.  The  alkalies  had  been  tried 
separately,  and  were  not  found  to  answer.  A  concentrated 
solution  is  formed  of  them,  with  which  the  sawdust  is  mixed  to 
the  consistence  of  a  thick  paste,  which  is  then  spread  in  thin 
layers  on  iron  plates,  and  gradually  heated  to  400^  F.,  at  which 
temperature  it  must  be  kept  for  an  hour  or  two.  The  heat  must 
not  exceed  this.  A  dark  brown  mass  is  thus  produced  which  is 
soluble  in  water.  Besides  oxalic  acid,  some  formic  acid  is  pro- 
duced, but  very  little  acetic.  Some  manipulation  here  followed, 
which  our  correspondent  failed  to  record,  and  after  it  the  mass 
