414  Manufacture  of  Chloral  Hydrate,  etc.  {^^JS?* 
tained,  is  placed  in  a  copper  still  lined  with  lead,  and  capable  of  hold- 
ing  from  300  to  400  pounds,  and  mixed  with  an  equal  weight  of  oil  of 
vitriol,  and  then  carefully  heated  over  an  open  charcoal  fire  to  the 
boiling  point.  A  considerable  quantity  of  muriatic  acid  is  thus  driven 
off,  while  the  chloral  vapors  are  condensed  by  an  upright  cooler.  The 
boiling  is  continued  until  hydrochloric  acid  ceases  to  be  given  off, 
which  usually  requires  seven  or  eight  hours  for  150  pounds  of  chloraL 
It  is  worthy  of  note  that  in  this  operation  the  contaminating  alcoholate 
of  chloral  is  entirely  destroyed. 
The  cooler  is  now  taken  away,  the  still  provided  with  a  thermom- 
eter, and  the  free  chloral  distilled  off.  At  first  the  liquid  boils  at 
95°  to  96°  F.,  and  by  the  time  the  thermometer  rises  to  100°  all  the 
chloral  has  gone  over,  and  the  distillation  may  be  stopped.  The  dis- 
tillate is  now  rectified  in  a  smaller  copper  retort  or  still,  holding  but 
150  to  180  pounds,  lined  with  lead,  and  provided  with  a  delicate  ther- 
mometer. Before  distilling,  the  free  hydrochloric  acid  still  remaining 
in  the  chloral  is  neutralized  with  triturated  chalk.  The  distilled 
chloral  is  caught  in  glass  flasks,  and  three  ounces  of  water  added  to 
every  four  pounds  of  chloral,  and  cooled  rapidly  by  continuous  shak- 
ing. If  required  to  be  crystallized,  it  is  emptied  into  large,  flat  por- 
celain dishes,  and  in  half  an  hour  forms  the  large,  flat  crystals  so 
much  in  demand  in  America.  These  are  broken  into  smaller  pieces 
and  packed  in  stone  jars  for  shipment.  Sometimes  it  is  dissolved  in 
chloroform,  from  which  it  crystallizes  in  about  a  week.  The  crystals 
are  freed  from  the  mother  liquor  by  a  centrifugal  machine,  and  dried 
in  a  closet  heated  by  steam.  The  mother  liquor  which  is  thrown  off 
can  be  used  to  dissolve  a  new  portion  instead  of  chloroform. 
Having  sketched  the  production  of  chloral  on  a  large  scale,  we 
may  now  look  after  the  by-products,  which  play  such  an  important 
role. 
Chloride  of  manganese  is  formed  in  immense  quantities,  and  unfor- 
tunately finds  but  little  use  in  the  arts.  Schering  has  collected  in 
two  years  about  5,000  carboys  of  this  solution,  and  no  small  capital 
is  invested  in  the  containing  vessels,  so  that  at  last  it  has  become 
necessary  to  throw  it  away. 
The  second  by-product  is  the  hydrochloric  acid  from  passing  chlo- 
rine through  the  alcohol  and  from  the  first  distillation.  This,  of 
course,  is  returned  to  the  chlorine  generator. 
The  etherial  liquid  which  collects  in  the  last  carboy,  under  the  by- 
