SODIUM  FOR  PHOSPHORUS  IN  LUCIFER  MATCHES.  257 
equivalents  of  carbon,  the  evolution  of  sulphuric  acid  is  less 
than  in  the  first  case,  and  the  mass  taken  up  by  the  water  yields 
sulphide  of  potassium  and  hyposulphite  of  potash :  sesquioxide 
of  chromium  obtained  under  these  conditions  must  be  separated, 
by  washing  in  acidulated  water,  from  a  certain  quantity  of  sul- 
phide of  chromium,  Cr2S3,  formed  by  contact  with  the  sulphide 
of  potassium.  It  is  better  to  decompose  the  alum  with  three 
equivalents  of  carbon  than  with  seven,  because  the  decomposition 
is  quicker  and  purer. 
The  industrial  treatment  of  chrome  alum  is  very  simple ;  it 
consists  of  pulverizing  and  mixing  the  alum  with  the  carbon,  and 
then  decomposing  it  at  red  heat  in  a  retort  of  refractory  earthen- 
ware. The  sulphuric  acid  passes  into  a  series  of  bitubular  flasks? 
containing  either  distilled  water,  carbonate  of  soda,  or  polysul- 
phide  of  sodium.  When  sulphuric  acid  is  no  longer  liberated, 
the  decomposition  is  ended.  The  obturator  of  the  retort  is  then 
withdrawn,  and  the  mass,  consisting  of  sulphate  of  potash  and 
sesquioxide  of  chromium,  is  caused  to  fall  into  a  cast-iron  boiler, 
water  is  added  and  the  whole  is  boiled  to  dissolve  the  sulphate 
of  potash,  which  is  afterwards  separated  by  crystallization  ;  the 
sesquioxide  of  chromium  is  placed  to  drain  upon  cloths,  and 
then  calcined  to  remove  the  water  that  remains.  This  oxide 
may  easily  be  rendered  chemically  pure  by  washing  it  in  a  boil- 
ing dilute  solution  of  carbonate  of  soda,  thus  removing  all  traces 
of  sulphuric  acid  which  had  escaped  the  action  of  the  pure  water. 
The  sesquioxide  of  chromium  obtained  by  this  process  is  of  too 
dull  a  green  to  be  used  for  printing  paper  or  textile  fabrics  ;  but, 
on  account  of  its  purity,  and  the  ease  with  which  it  may  be  treated, 
it  is  perfectly  adapted  for  making  bichromate  of  potash — Chem, 
News,  Feb.  2Qth,  1869,  from  Comptes  Rendus. 
 4  ^  
ON  THE  SUBSTITUTION  OF  SODIUM  FOR  PHOSPHORUS 
IN  LUCIFER  MATCHES. 
Dr.  II  Fleck,  of  Dresden,  has  instituted  a  series  of  experi- 
ments with  the  view  to  obtain  a  non-poisonous  paste  for  the 
application  to  lucifer  matches.  He  ascertained,  by  some  pre- 
liminary experiments,  that  sodium,  when  minutely  divided  along 
17 
9 
