58  PHOSPHORUS  AND  MATCH  MANUFACTURES. 
shallow  copper  pans,  and  allowed  to  solidify.  It  is  then  broken 
under  water,  and  the  pieces  are  placed  in  hot  water  in  a  double- 
sided  (or  steam-jacketed)  vertical  iron  cylinder,  lined  with  lead, 
with  a  perforated  bottom  covered  with  chamoisleather  and  canvass, 
and  while  in  the  fluid  state  pressure  is  applied  to  the  phosphorus, 
and  it  passes  through  the  leather,  &c,  into  a  vessel  of  hot  water 
beneath,  leaving  the  residuary  impurities,  red  phosphorus,  &c, 
upon  the  cloth  in  the  form  of  a  dirty  reddish  substance  of  an 
earthy  appearance. 
The  bleached  and  purified  phosphorus  is  now  cast  into  wedge- 
shaped  pieces,  or  it  is  moulded  into  cylindrical  sticks,  half  an 
inch  in  diameter,  and  ten  inches  long,  by  the  aid  of  glass  tubes 
immersed  into  the  phosphorus  under  water,  or  by  means  of  an 
apparatus  with  tubes  specially  contrived  for  the  purpose.  On 
some  occasions  the  phosphorus  is  very  brittle  and  difficult  to 
draw  into  sticks,  but  if  it  is  in  a  satisfactory  pure  state  it  is  as 
ductile  as  lead  or  soft  copper  wire.  The  appearance  of  the 
purified  phosphorus  in  the  form  of  wedges  is  that  of  very  trans- 
parent wax  or  glass  of  a  slightly  greenish-yellow  color,  but  when 
in  the  form  of  sticks  it  usually  appears  colorless.  It  is  needful 
on  all  occasions  to  protect  the  purified  substance  from  strong 
daylight,  otherwise  it  soon  becomes  yellow  and  opaque.  For 
conveyance  it  is  always  packed  in  water,  generally  in  tin  cans, 
the  covers  of  which  are  soldered  air-tight. 
The  phosphorus  we  have  described  is  that  of  the  ordinary 
kind,  but  there  is  another  variety  equally  pure,discovered  in  1848 
by  Professor  Schrotter,  of  Vienna,  which  is  produced  as  follows  : 
The  ordinary  phosphorus  in  its  purified  state  is  placed  under 
water  in  a  cast-iron  boiler  over  a  furnace  ;  then  melted,  cooled, 
and  the  water  removed  from  its  surface.  The  vessel  is  then  im- 
mediately and  securely  closed,  air-tight  (except  a  small  iron- 
tube  for  the  escape  of  vapor),  by  a  cast-iron  cover.  The  lid  has 
a  vertical  iron  tube,  closed  at  its  lower  end,  fixed  in  it,  which 
projects  downwards  into  the  phosphorus,  and  is  open  at  its  upper 
end  for  the  reception  of  a  thermometer.  Heat  is  now  gradually 
applied  by  means  of  the  furnace  until  the  phosphorus  is  at  about 
450°  Fah.,  and  that  temperature  is  maintained  for  a  greater 
or  less  period  of  time,  according  to  the  amount  of  phosphorus 
operated  upon,  and  the  mass  is  then  allowed  to  cool.    A  quan- 
