Am,MJa°y,ri9warm*}  Conservation  and  Chemical  Engineer.  235 
of  residues  is  also  a  feature  of  recent  years.  From  these  residues 
are  now  made  excellent  road  oils  for  the  aid  of  the  good  roads  move- 
ment. The  petroleum  pitch  is  all  utilized  also,  partly  for  electric 
light  carbons  and  partly  for  fuel  purposes.  Most  promising  of  all. 
however,  is  the  result,  not  as  yet  fully  attained,  but  most  certain  of 
solution  in  the  immediate  future,  viz.,  the  utilization  of  crude  petro- 
leum of  the  lesser  valuable  kinds  and  residuums  in  internal  com- 
bustion engines  for  the  development  of  power. 
A  second  typical  industry  is  that  of  coal  distillation.  We  have 
already  spoken  of  the  wastage  in  the  mining  of  coal.  It  is  not  neces- 
sary here  to  speak  of  the  corresponding  waste  in  its  utilization  as 
fuel.  We  will  speak  solely  of  the  distillation  of  coal.  This  treat- 
ment may  be  carried  out  from  either  one  of  two  points  of  view,  and 
the  exploitation  in  each  case  has  been  pushed  with  great  energy, 
utilizing  all  available  chemical  and  engineering  skill.  The  first  is 
the  distillation  for  the  manufacture  of  illuminating  gas.  While 
the  mechanical  side  of  this  process  has  advanced  steadily,  particu- 
larly after  the  introduction  of  regenerative  firing  and  mechanical 
stoking,  the  chemical  side  did  not  advance  so  rapidly.  While  the 
coal-tar  is  no  longer  thrown  away,  unless  it  be  in  very  isolated 
localities,  the  proper  chemical  utilization  of  this  tar  has  lagged  be- 
hind both  in  this  country  and  in  England.  On  the  other  hand, 
the  true  conservation  of  this  valuable  side-product  and  the  develop- 
ment of  its  possibilities  has  advanced  in  a  notable  degree  in  Germany, 
the  home  of  the  coal-tar  industry.  Here  the  research  chemist 
and  the  chemical  engineer  have  gone  hand  in  hand  in  the  building 
up  of  a  great  industry  or  rather  two  industries  based  upon  the 
utilization  of  the  coal-tar,  the  manufacture  of  the  coal-tar  dye  colors, 
and  the  manufacture  of  synthetic  medical  preparations  possessing 
valuable  therapeutic  characteristics.  Besides  these  most  important 
and  highly  developed  illustrations  of  conservation,  we  have,  how- 
ever, some  minor  utilizations  of  coal-tar  or  products  from  the  same 
that  deserve  mention.  Thus  the  manufacture  of  creosote  oils  for 
the  preservative  treatment  of  wood,  the  roofing-pitch  and  tar-paper 
manufacture  and  the  use  of  pitch  in  the  biquetting  of  coal  are  illus- 
trations of  value  given  to  the  coal-tar  and  its  products. 
The  thorough  extraction  of  the  ammonia  and  the  impurities 
like  the  cyanides  from  the  ammoniacal  liquor  and  the  production  of 
commercially  valuable  products  from  them  is,  moreover,  an  accom- 
plishment in  the  way  of  conservation.    The  utilization,  too,  of  the 
