"""siX'isrs™*}    ^development  of  the  Chemical  Arts,  419 
corresponds  with  the  latter  assumption  only.  Another  experiment  seems 
to  them  even  more  decisive  against  Balard's  theory,  viz.,  that  one  gram 
bleaching  powder,  boiled  with  a  solution  of  phosphoric  acid  and  precip- 
itated with  argentic  nitrate,  only  shows  2*99  per  cent.  CaCl.  On  the 
other  hand,  their  experiments  again  show  that  a  solution  of  bleaching 
powder  behaves  like  a  mixture  of  calcium  hypochlorite  and  calcium  chlo- 
ride. Last  of  all,  R.  and  J.  controvert  Goepner's  idea  that  the  constant 
presence  of  free  calcium  hydrate  in  bleach  is  attributable  to  its  being  pro- 
tected by  calcium  chloride,  but  they  seek  the  explanation  of  the  above 
in  the  fact,  first  established  by  Graham,  that  perfectly  dry  calcium 
hydrate  is  not  acted  upon  by  chlorine,  and  they  show  that  it  is  indifferent 
whether  the  calcium  hydrate  is  deprived  of  its  moisture  by  heat,  or  by 
the  presence  of  other  bodies  having  a  greater  attraction  for  water,  such 
as  calcium  chloride,  or  even  the  bleaching  compound  CaOCl,  whose 
hygroscopic  properties  are  well  known. — Amer,  Chem.^  June,  1875,  from 
Trans.  Newcastle-upon-Tyne  Chem.  Soc, 
REPORT  ON  THE  DEVELOPMENT  OF  THE  CHEMICAL  ARTS  DUR- 
ING THE  LAST  TEN  YEARS  * 
BY  DR.  A.  W.  HOFMANN. 
(Continued  from  page  369.) 
The  air  is  driven,  by  means  of  a  blast,  at  a  pressure  of  3  to  4  c.  m. 
of  mercury,  through  a  sheet-iron  box  filled  with  caustic  lime,  and  then 
conducted  into  the  retort  from  above.  The  temperature  of  the  latter 
can  be  judged  by  means  of  an  aperture,  which  can  be  closed  with  an 
iron  stopper.  The  air  gives  off  only  about  the  half  of  its  oxygen,  so 
that,  for  I  volume  of  oxygen  10  volumes  of  air  must  be  passed  through, 
the  residue  escaping  into  the  atmosphere. f  In  about  five  minutes  the 
revivification  of  the  reduced  mass  is  completed,  when  the  stream  of  air 
is  cut  off"  by  means  of  a  cock  with  a  triple  perforation,  and  a  current  of 
superheated  steam  is  passed  through  for  five^  minutes,  whilst  immediately 
afterwards  the  gas  which  issues  below  the  grate  is  conducted  into  condens- 
ers. Here,  a  fine  descending  rain  of  cold  water  frees  the  oxygen  from 
steam,  and  it  enters  the  gasometer  under  the  pressure  of  a  column  of  water 
"  Berichte  liber  die  Entwickelung  der  Chemischen  Industrie  Wahrend.  des 
Letzten  Jahrzehends." 
t  Latterly,  Tessie  du  Motay  has  attempted  to  convert  the  escaping  nitrogen  in- 
dustrially, first  into  nitride  of  titanium,  and  then  into  ammonia. 
