262 
Chemical  Notes. 
Am.  Jour.  Pharira 
May,  1880. 
first  that  many  bodies,  such  as  silica,  alumina  and  oxide  of  zinc,  which 
are  insoluble  in  water  at  ordinary  temperatures,  dissolve  to  a  very  con- 
siderable extent  when  treated  with  water-gas  at  a  very  high  pressure- 
It  occurred  to  him  that  a  solvent  might  be  found  for  carbon,  and  as 
gaseous  solution  nearly  always  yields  crystalline  solid  on  withdrawing; 
the  solvent  or  lowering  its  solvent  power,  it  seemed  probable  that  the 
carbon  might  be  deposited  in  the  crystalline  state.  Ordinary  carbon,, 
such  as  charcoal,  lampblack  or  graphite  was  found  not  to  be  acted 
upon.  It  was  found,  however,  that  carbon  could  be  gotten  in  the 
nascent  state  by  the  following  reaction.  When  a  gas  containing  car- 
bon and  hydrogen  is  heated  under  pressure  in  presence  of  certain  metals,, 
its  hydrogen  is  attracted  by  the  metal  and  its  carbon  left  free.  When- 
the  carbon  is  set  free  in  presence  of  a  stable  compound  containing 
nitrogen,  the  whole  being  near  a  red  heat  and  under  a  very  high  pres- 
sure, the  carbon  is  so  acted  upon  by  the  nitrogen  compound  that  it  is 
obtained  in  the  clear  transparent  form  of  the  diamond.  The  carbon  sa 
obtained  is  as  hard  as  natural  diamond,  scratching  all  other  crystals,  and 
it  does  not  affect  polarized  light.  The  crystals  have  curved  faces 
belonging  to  the  octahedral  form  ;  they  burn  easily  on  thin  platinurrb 
foil,  leaving  no  residue,  and  after  two  days'  immersion  in  hydrofluoric 
acid  they  show  no  sign  of  dissolving  even  when  boiled. — Chem.  NewSy 
March  5th,  1880. 
Dissociation  of  Chlorine^  Bromine  and  Iodine. -^^hG.  first  results  of  Victor 
Meyer  on  this  subject  have  already  been  noted  (this  Journal,  Sept.^ 
1879).  J.  M.  Crafts  has  repeated  these  experiments,  working  with 
slightly  modified  apparatus.  Using  free  chlorine,  instead  of  the  nas- 
cent chlorine  evolved  from  platinum  chloride,  he  found  no  change  in 
the  vapor  density  of  the  gas  even  at  the  highest  temperature  of  the  fur- 
nace. With  iodine,  however,  he  did  find  the  change  in  vapor-density 
referred  to  by  Victor  Meyer,  viz  ,  a  reduction  to  two-thirds  the  normal 
value.  With  bromine  he  got  results  giving  a  value  intermediate  between 
the  normal  and  the  two-thirds  value. 
Victor  Meyer  and  Lliblin  now  publish  results  obtained  by  them 
prior  to  the  publication  of  Craft's  paper  bearing  upon  the  same  subjects 
They  found  also  that  free  chlorine  gave  a  normal  density  under  all 
changes  of  temperature,  so  that  it  is  only  when  nascent  chlorine  is  tried 
rhat  the  abnormal  density  or  dissociation,  as  they  view  it,  is  gotten. 
Iodine,  however,  taken  in  the  free  state,  showed  dissociation  at  all 
temperatures  over  about  i,ooo°C.    With  bromine,  if  the  free  element 
