236  Conservation  and  Chemical  Engineer.  {  Am,^uri9I[oarm" 
gas  carbon  for  the  manufacture  of  electrode  carbons,  battery  plates 
and  for  electric  light  carbons  is  another  illustration  of  this  work. 
The  second  method  of  distilling  coal  is  that  for  the  production  of 
coke  for  metallurgical  purposes.  This  has  been  developed  or  more 
properly  exploited  to  such  a  degree  that,  according  to  the  "  Mineral 
Resources  of  the  United  States,"  published  by  the  U.  S.  Geological 
Survey,  the  production  of  coke  for  the  year  1907  was  40,779,564  tons, 
of  which,  however,  35,171,665  tons  were  produced  in  beehive  ovens. 
In  these  as  is  well  known,  only  the  fixed  carbon  of  the  bituminous 
coal  is  saved  and  all  volatile  constituents  including  gas,  tar,  and 
ammonia  are  absolutely  wasted.  On  the  other  hand,  5,607,899  tons 
of  coke  were  produced  in  by-product  recovery  ovens  and  the  value  of 
the  by-products  (gas,  tar,  and  ammonia)  obtained  therefrom  amounted 
to  $7,548,071.  It  is  easy  to  reckon  from  this  what  the  loss  was 
on  the  35,171,665  tons  of  coke  made  in  beehive  ovens.  In  fact,  the 
article  on  "  Coal,"  in  Bulletin  394  before  referred  to<  says  with 
reference  to  this,  "  at  the  prices  which  prevailed  in  1907,  the  value 
of  the  by-products  wasted  in  beehive  coke-ovens  was  a  little  over 
$55,000,000." 
But  the  result  achieved  by  the  chemical  engineer  in  the  working 
of  this  by-product  over  represents  more  than  merely  saving  certain 
by-products.  The  gas  produced  can  be  separated  by  the  perfect 
control  of  the  method  into  "  poor  gas  "  for  fuel  purposes  and  "  rich 
gas  "  for  illuminating  purposes,  so  that  the  highest  economy  or 
conservation  of  values  is  thereby  attained. 
Another  industry  in  which  the  chemical  engineer  has  worked 
first  for  the  purpose  of  exploitation  and  later  for  conservation  of 
material  and  values  is  the  starch  industry.  Starch,  as  we  all  know, 
is  one  of  the  most  widely  distributed  vegetable  products  and  has 
always  played  a  great  part  in  the  world's  supply  of  food.  In 
Europe,  it  is  potato  and  wheat  starch,  in  the  United  States  it  is  corn 
starch,  and  in  tropical  countries  it  is  rice,  tapioca,  sago,  etc.,  that  are 
the  important  varieties  of  this  cereal  food.  Not  only  has  the  produc- 
tion of  starch  been  developed,  however,  for  food  purposes,  but  enor- 
mous quantities  of  the  starchy  substances  serve  as  the  starting  point 
in  the  fermentation  industries.  Then  we  have  the  -use  of  both 
starch  and  its  alteration  product,  dextrine,  in  the  textile  industries 
and  the  production  of  glucose  as  the  product  of  the  hydrolysis  of 
starch,  and  the  manufacture  of  nitro-starch  and  its  utilization  in  the 
explosives  industry.    All  of  these  industries  have  attained  a  high 
