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RELATION  OF  HYDROGEN  TO  PALLADIUM. 
of  magnesia  (to  make  the  flame  luminous),  burns  like  a  waxed 
thread  when  ignited  in  the  flame  of  a  lamp. 
[The  foregoing  is  about  a  quarter  of  the  paper  of  Prof.  Graham, 
which  is  too  long  for  insertion  in  this  journal.  What  follows  is 
an  abbreviation  of  the  remainder. — Ed.  Am.  Jour.  Pharm.] 
Expt.  2. — Another  portion  of  the  same  palladium  wire  was 
charged  as  before  with  hydrogen.  Length  of  wire  488*976  m.m., 
gas  occluded,  867*15]volumes  ;  linear  elongation  6*68  m.m.;  den- 
sity of  hydrogenium  1*898. 
Uxpt.  3. — Length  of  wire  556*185  m.m.,  gas  occluded  888*303 
volumes;  linear  elongation  7*467  m.  m. ;  density  of  hydrogenium 
1*977. 
Various  other  experiments  were  made,  showing  a  remarkable 
approximation  in  density,  except  in  one  instance,  which  was  con- 
sidered exceptional— viz  :  2*055,  1*930,  1*927,  1*917,  1*898, 
1*977,  1*708.  The  mean  density  excluding  the  last  is  1-951  or 
nearly  2. 
A  curious  result  was  that,  in  charging  and  discharging  of  the 
same  palladium  wire,  it  became  shorter  each  time,  but  as  the 
specific  gravity  of  the  metal  was  unaltered,  it  follows  that  the 
the  contraction  in  length  was  accompanied  by  expansion  in  diam- 
eter. Repeated  experiment  on  the  same  wire  reduced  its  length 
15  per  cent.  This  retraction  was  also  proved  to  not  be  due  to  heat, 
as  it  occurred  when  the  hydrogen  was  removed  at  the  ordinary 
temperature  by  making  it,  the  wire,  the  positive  electrode  of  the 
battery  so  as  to  oxidize  the  hydrogen.  Repeated  charging  and 
discharging  by  heat  reduced  the  absorbing  capacity  of  the  wire 
to  one-third.  This  capacity  is  partially  restored  by  the  passage 
of  an  electrical  current  while  red  hot,  and  may  be  restored  fully 
by  extracting  the  hydrogen  by  electrolysis  in  an  acid  fluid.  The 
molecular  structure  of  the  palladium  appears  to  undergo  great 
changes  by  the  repeated  absorption  and  removal  of  the  hydrogen. 
2.  Tenacity. — Palladium  wire  similar  to  the  last  was  broken 
by  from  10  to  10*17  kilogrammes  weight ;  when  charged  with 
hydrogen  it  was  broken  on  an  average  by  8*22  kilogrammes. 
The  tenacity  of  the  palladium  is  found  to  be  somewhat  reduced 
after  the  removal  of  the  hydrogen. 
3.  Electrical  Conductivity. — Careful  experiments  by  Mr.  Beck- 
er gave  the  relative  conducting  power  of  the  metal  and  alloy 
