368  Development  of  the  Chemical  Arts.    {  ^"^-^nZ'^^n'^' 
mediately  resolved  into  cupric  chloride  and  free  chlorine,  but  which,  if 
heated  to  400°,  gives  off  all  its  oxygen.  One  kilo,  of  cuprous  chlo- 
ride yields  28  to  30  litres  of  oxygen.  In  experiments  on  the  large 
scale,  100  kilos,  of  cuprous  chloride  yielded  either  3  to  3!^  cubic  metres 
of  chlorine.  As  four  or  five  such  operations  can  be  conducted  daily, 
200  to  300  kilos,  of  cuprous  chloride  could  be  made  to  yield  daily  15 
to  18  cubic  metres  of  oxygen.  The  requisite  apparatus  consists  of 
*  rotatory  cast-iron  retorts  lined  with  clay,  which  contain  the  cuprous 
chloride  mixed  with  one-third  sand  or  kaolin  to  diminish  its  fusibility. 
This  process  was  carried  out  in  Cologne  in  187 1.*  A  company  estab- 
lished at  Paris  for  the  utilization  of  the  process  flourished  for  a  short 
time  only,t  probably  because  it  was  superseded  by  an  analogous  pro- 
cess. 
We  refer  to  the  method  which  has  been  developed  since  1867I  by 
the  suggestive  inventor,  Tessie  du  Motay.  Its  transferrer  of  oxygen 
is  the  black  oxide  of  manganese,  and  it  is  based  upon  the  following 
reactions  :  Hydrate  of  soda,  according  to  Mitscherlich,  if  heated  to 
dull  redness  in  contact  with  air  and  black  oxide  of  manganese,  yields 
manganate  of  soda  and  water — 
4NaOH+2Mn02+20=2Na2MnO,-f2H20. 
Manganate  of  soda  at  the  same  temperature  in  a  current  of  dry  su- 
perheated steam  is  resolved  again  into  hydrate  of  soda,  sesquioxide  of 
manganese,  and  free  oxygen — 
2NaMnO,+2H20=4NaOH-Mn203+30. 
The  only  condition,  then,  is  to  free  the  superheated  air  previously 
from  carbonic  acid,  in  order  to  obtain  a  mixture  which  shall  he  perpet- 
ually efficient.  This  method  has  been  found  satisfactory  on  repeated 
scrutiny,  and  has  been  applied  on  the  large  scale  at  Comines  (near 
Lille),  at  Pantin  (near  Paris),  New  York,  Brussels,  and  Vienna. 
Bothe||  reports  that  a  melting  of  60  parts  of  dry  carbonate  of  soda 
with  40  parts  of  peroxide  of  manganese  at  95  per  cent,  yielded,  accord- 
ing to  analysis  74*62  of  manganate  of  soda,  and  that  40  kilos,  of  this 
substance,  which,  according  to  theory,  should  yield  2036  cubic  decime- 
tres of  oxygen,  actually  produced  1800,  or  90  per  cent,  of  the  calcu- 
^  Phillips,  "Der  SauerstofF"  (Berlin,  1871),  22, 
t  Wagner,  "  Jahresberichte,"  1867,  215. 
%  Tessie  du  Motay,  "  Institut,"  1868,  48. 
II  Bothe,     Zeitschr.  d.  Vereins  Deutsch.  Ing.,"  1867,  334. 
