﻿64 
  M. 
  C. 
  Lea 
  — 
  Experiment 
  with 
  Gold. 
  

  

  Art. 
  VI. 
  — 
  An 
  Experiment 
  with 
  Gold 
  ; 
  by 
  M. 
  Carey 
  Lea. 
  

  

  Sometime 
  since 
  I 
  had 
  occasion 
  to 
  reduce 
  a 
  number 
  of 
  gold 
  

   solutions 
  and 
  used 
  for 
  this 
  purpose 
  sodium 
  hypophosphite. 
  

   The 
  solutions 
  all 
  acted 
  in 
  the 
  usual 
  way 
  with 
  one 
  exception 
  ; 
  

   in 
  this 
  the 
  liquid 
  turned 
  deep 
  emerald 
  green. 
  This 
  condition 
  

   lasted 
  about 
  ten 
  minutes 
  and 
  then 
  the 
  metal 
  was 
  precipitated. 
  

  

  I 
  have 
  since 
  determined 
  the 
  conditions 
  under 
  which 
  this 
  

   appearance 
  takes 
  place 
  and 
  its 
  explanation. 
  

  

  A 
  weighed 
  quantity 
  of 
  pure 
  gold 
  was 
  dissolved 
  and 
  the 
  

   solution 
  was 
  evaporated 
  to 
  dryness 
  twice. 
  The 
  chloride 
  was 
  

   then 
  dissolved 
  in 
  water 
  in 
  the 
  proportion 
  of 
  1 
  gram 
  of 
  metallic 
  

   gold 
  to 
  each 
  10 
  cc 
  of 
  solution. 
  A 
  10 
  per 
  cent 
  solution 
  of 
  sodium 
  

   hypophosphite 
  w 
  r 
  as 
  also 
  made. 
  These 
  solutions 
  mixed 
  in 
  vari- 
  

   ous 
  proportions 
  produced 
  the 
  green 
  solution 
  ; 
  perhaps 
  the 
  

   most 
  satisfactory 
  result 
  was 
  obtained 
  as 
  follows 
  : 
  

  

  Of 
  the 
  hypophosphite 
  solution 
  15 
  cc 
  are 
  to 
  be 
  placed 
  in 
  a 
  

   beaker 
  and 
  l 
  cc 
  of 
  the 
  gold 
  solution 
  is 
  to 
  be 
  added 
  and 
  then 
  one 
  

   drop 
  of 
  sulphuric 
  acid. 
  As 
  soon 
  as 
  the 
  solution 
  begins 
  to 
  

   darken 
  a 
  little, 
  which 
  will 
  be 
  in 
  from 
  two 
  to 
  four 
  minutes, 
  30 
  cc 
  

   of 
  water 
  are 
  to 
  be 
  added 
  without 
  delay. 
  The 
  solution 
  presently 
  

   assumes 
  a 
  deep 
  green 
  color, 
  remaining 
  quite 
  transparent. 
  By 
  

   slow 
  degrees 
  it 
  becomes 
  less 
  clear. 
  If 
  filtered 
  at 
  the 
  end 
  of 
  an 
  

   hour 
  the 
  filtrate 
  will 
  either 
  be 
  yellow 
  or 
  green 
  ; 
  if 
  yellow 
  it 
  

   soon 
  turns 
  green, 
  remaining 
  for 
  some 
  time 
  transparent; 
  and 
  this 
  

   may 
  be 
  repeated 
  several 
  times. 
  

  

  One 
  explanation 
  presented 
  itself 
  — 
  that 
  there 
  might 
  be 
  present 
  

   in 
  a 
  state 
  of 
  fine 
  division 
  the 
  olive 
  green 
  oxide 
  of 
  gold 
  Au 
  2 
  2 
  

   described 
  by 
  Prat.* 
  But 
  in 
  the 
  filtrations 
  above 
  referred 
  to 
  

   there 
  is 
  left 
  on 
  the 
  filter 
  an 
  infinitesimal 
  quantity 
  of 
  a 
  blueish 
  

   black 
  substance 
  which 
  is 
  not 
  an 
  oxide 
  but 
  metallic 
  gold. 
  

  

  The 
  green 
  color 
  of 
  the 
  liquid 
  is, 
  therefore, 
  due 
  to 
  the 
  presence 
  

   of 
  a 
  small 
  quantity 
  of 
  gold 
  in 
  its 
  blue 
  form 
  in 
  a 
  state 
  of 
  very 
  

   fine 
  division, 
  which 
  together 
  with 
  the 
  yellow 
  of 
  the 
  undecom- 
  

   posed 
  solution 
  gives 
  the 
  effect 
  of 
  green. 
  

  

  If 
  when 
  the 
  solution 
  becomes 
  slightly 
  troubled, 
  instead 
  of 
  

   filtering 
  it 
  is 
  left 
  to 
  itself 
  for 
  a 
  few 
  minutes, 
  the 
  sides 
  of 
  the 
  

   beaker 
  will 
  receive 
  a 
  deposit 
  of 
  gold, 
  yellowish 
  brown 
  by 
  

   reflected 
  light 
  but 
  clear 
  blue 
  by 
  transmitted. 
  

  

  * 
  Roscoe 
  & 
  Schorlemrner, 
  vol. 
  ii, 
  part 
  2, 
  page 
  377. 
  

  

  