﻿E. 
  V.Shannon 
  — 
  Crystals 
  of 
  Pyromorphite. 
  327 
  

  

  analysis 
  on 
  insufficient 
  material 
  gave 
  approximately 
  lead 
  75 
  

   per 
  cent 
  and 
  chlorine 
  3 
  per 
  cent. 
  The 
  composition 
  thus 
  

   corresponds 
  to 
  ordinary 
  pyromorphite. 
  

  

  2. 
  Pyromorphite 
  from 
  Broken 
  Hill, 
  New 
  South 
  Wales. 
  

  

  For 
  purposes 
  of 
  comparison 
  Col. 
  Roebling 
  very 
  kindly 
  loaned 
  

   the 
  author 
  a 
  recently 
  acquired 
  specimen 
  of 
  pyromorphite 
  from 
  

   Broken 
  Hill. 
  The 
  specimen 
  consists 
  of 
  an 
  irregular 
  mass 
  of 
  

   iron 
  oxides 
  completely 
  encrusted 
  with 
  glittering 
  microscopic 
  

   crystals 
  of 
  gray 
  pyromorphite. 
  Measurement 
  on 
  the 
  reflecting 
  

   goniometer 
  showed 
  that 
  the 
  dominant 
  _forms 
  present 
  were 
  the 
  

   prism 
  a 
  (1120) 
  and 
  the 
  pyramid 
  s 
  (1121) 
  of 
  the 
  second 
  order 
  

   and 
  the 
  prism 
  m 
  (1010) 
  of 
  the 
  first 
  order 
  with 
  a 
  small 
  base 
  and 
  

   an 
  occasional 
  pyramid 
  of 
  the 
  first 
  order. 
  The 
  habit 
  is 
  thus 
  

   quite 
  unlike 
  the 
  Idaho 
  material. 
  Figure 
  2 
  shows 
  the 
  appearance 
  

   of 
  these 
  crystals. 
  

  

  SCIENTIFIC 
  INTELLIGENCE. 
  

  

  I. 
  Chemistry 
  and 
  Physics. 
  

  

  1. 
  The 
  Penfield 
  Test 
  for 
  Carbon— 
  W. 
  G. 
  Mixtee 
  and 
  F. 
  L. 
  

   Hajgh 
  have 
  made 
  an 
  interesting 
  examination 
  of 
  the 
  delicacy 
  of 
  

   this 
  method 
  which 
  was 
  originally 
  devised 
  for 
  testing 
  for 
  carbon 
  

   and 
  carbonates 
  in 
  minerals. 
  They 
  observe 
  that 
  the 
  method 
  does 
  

   not 
  appear 
  to 
  be 
  in 
  the 
  literature 
  of 
  analytical 
  chemistry. 
  It 
  is 
  

   novel 
  only 
  in 
  the 
  very 
  delicate 
  way 
  in 
  which 
  the 
  late 
  Professor 
  

   S. 
  L. 
  Penfield 
  applied 
  well-known 
  reactions. 
  He 
  fused 
  the 
  sub- 
  

   stance 
  to 
  be 
  tested 
  with 
  lead 
  chromate 
  in 
  a 
  small 
  horizontal 
  hard 
  

   glass 
  tube, 
  closed 
  at 
  the 
  heated 
  end, 
  and 
  containing 
  near 
  the 
  open 
  

   end 
  a 
  small 
  drop 
  of 
  barium 
  hydroxide 
  solution. 
  The 
  appearance 
  

   of 
  a 
  film 
  of 
  barium 
  carbonate 
  indicates 
  the 
  presence 
  of 
  carbon 
  in 
  

   the 
  substance. 
  If 
  no 
  film 
  is 
  seen 
  when 
  the 
  fusion 
  is 
  effected, 
  the 
  

   open 
  end 
  of 
  the 
  tube 
  may 
  be 
  closed 
  with 
  the 
  finger 
  to 
  keep 
  out 
  

   carbon 
  dioxide 
  from 
  the 
  air 
  and 
  the 
  tube 
  may 
  be 
  removed 
  from 
  

   the 
  flame 
  so 
  that 
  the 
  result 
  may 
  be 
  more 
  carefully 
  observed. 
  

  

  The 
  method 
  has 
  been 
  used 
  by 
  Professor 
  Mixter 
  in 
  the 
  Sheffield 
  

   Chemical 
  Laboratory 
  for 
  a 
  number 
  of 
  years, 
  especially 
  for 
  test- 
  

   ing 
  metals 
  for 
  carbon. 
  It 
  is 
  so 
  delicate 
  that 
  lead 
  chromate 
  

   which 
  has 
  been 
  exposed 
  to 
  the 
  air 
  in 
  preparation 
  will 
  react 
  for 
  

   carbon, 
  but 
  the 
  reagent 
  may 
  be 
  freed 
  from 
  carbon 
  by 
  heating 
  it 
  

   below 
  its 
  sintering 
  point 
  in 
  an 
  atmosphere 
  of 
  oxygen. 
  Special 
  

   precautions 
  are 
  necessary 
  also 
  to 
  clean 
  thoroughly 
  the 
  glass 
  tubes 
  

   used 
  for 
  the 
  experiments, 
  and 
  to 
  protect 
  them 
  from 
  dust. 
  

  

  