﻿312 
  M. 
  C. 
  Lea—Allotropic 
  Silver. 
  

  

  oxidation 
  of 
  the 
  former 
  reagent 
  ; 
  and, 
  after 
  the 
  addition 
  of 
  

   1 
  grm. 
  of 
  tartaric 
  acid 
  to 
  every 
  0'2 
  grm. 
  of 
  antimonious 
  oxide, 
  

   the 
  acid 
  present 
  is 
  nearly 
  neutralized 
  with 
  sodium 
  hydrate, 
  the 
  

   neutralization 
  being 
  completed 
  by 
  hydrogen 
  sodium 
  carbonate 
  

   added 
  in 
  excess 
  to 
  an 
  amount 
  corresponding 
  to 
  10 
  cm. 
  3 
  of 
  the 
  

   saturated 
  solution 
  for 
  every 
  01 
  grm. 
  of 
  antimonious 
  oxide 
  

   present. 
  Titration 
  with 
  decinormal 
  iodine 
  standardized 
  against 
  

   tartar 
  emetic 
  gives 
  the 
  antimony 
  quickly 
  and 
  with 
  a 
  fair 
  degree 
  

   of 
  accuracy. 
  The 
  whole 
  process 
  requires 
  about 
  an 
  hour 
  and 
  a 
  

   half 
  for 
  completion. 
  

  

  Akt. 
  XXX. 
  — 
  Notes 
  on 
  Allotropic 
  Silver 
  ; 
  by 
  M. 
  Cakey 
  Lea. 
  

  

  Relations 
  of 
  the 
  Yellow 
  to 
  the 
  Blue 
  Forms. 
  — 
  The 
  gold-and 
  

   copper-colored 
  forms 
  on 
  the 
  one 
  hand, 
  and 
  the 
  blue, 
  bluish- 
  

   green 
  and 
  steel-gray 
  on 
  the 
  other 
  hand 
  stand 
  in 
  close 
  relations 
  

   to 
  each 
  other. 
  In 
  previous 
  papers 
  there 
  has 
  been 
  described 
  a 
  

   crystalline 
  state 
  intermediate 
  between 
  these 
  active 
  forms 
  and 
  

   ordinary 
  silver, 
  which 
  intermediate 
  condition, 
  while 
  retaining 
  

   the 
  bright 
  yellow 
  color 
  of 
  the 
  active 
  form 
  is 
  nearly 
  as 
  indif- 
  

   ferent 
  to 
  reagents 
  as 
  ordinary 
  silver. 
  Into 
  this 
  intermediate 
  

   state 
  both 
  the 
  yellow 
  and 
  blue 
  forms 
  are 
  capable 
  of 
  passing, 
  

   and 
  apparently 
  the 
  intermediate 
  states 
  of 
  both 
  kinds 
  of 
  allo- 
  

   tropic 
  silver 
  are 
  identical 
  : 
  the 
  intermediate 
  form 
  of 
  blue 
  silver 
  

   is 
  yellow. 
  Thus 
  when 
  lumps 
  of 
  blue 
  silver 
  are 
  heated 
  in 
  a 
  

   test 
  tube 
  to 
  about 
  180° 
  C. 
  they 
  assume 
  a 
  gold 
  color 
  and 
  luster. 
  

   The 
  same 
  change 
  takes 
  place 
  at 
  the 
  same 
  temperature 
  when 
  

   films 
  of 
  blue 
  silver 
  are 
  placed 
  in 
  a 
  hot 
  air 
  bath. 
  

  

  But 
  relations 
  much 
  closer 
  than 
  these 
  exist. 
  Blue 
  silver 
  can 
  

   be 
  converted 
  into 
  yellow 
  at 
  ordinary 
  temperatures 
  and 
  conse- 
  

   quently 
  with 
  retention 
  of 
  its 
  active 
  properties. 
  This 
  is 
  accom- 
  

   plished 
  through 
  the 
  agency 
  of 
  sulphuric 
  acid. 
  "When 
  a 
  

   solution 
  of 
  silver 
  is 
  obtained 
  by 
  the 
  action 
  of 
  sodium 
  hy- 
  

   droxide 
  and 
  dextrine 
  on 
  silver 
  nitrate* 
  it 
  appears 
  to 
  contain 
  

   the 
  blue 
  variety, 
  for 
  if 
  allowed 
  to 
  precipitate 
  spontaneously 
  by 
  

   long 
  standing, 
  or 
  if 
  precipitated 
  by 
  acetic 
  acid, 
  dilute 
  nitric 
  

   acid, 
  or 
  by 
  many 
  neutral 
  substances, 
  it 
  gives 
  a 
  form 
  of 
  silver 
  

   which 
  is 
  dark 
  red 
  while 
  moist 
  and 
  dries 
  with 
  a 
  blue 
  surface 
  

  

  * 
  Forty 
  grams 
  each 
  of 
  sodium 
  hydroxide 
  and 
  of 
  yellow 
  or 
  brown 
  dextrine 
  (not 
  

   white) 
  are 
  dissolved 
  in 
  two 
  litres 
  of 
  water 
  and 
  28 
  grams 
  of 
  silver 
  nitrate 
  in 
  solu- 
  

   tion 
  are 
  added 
  in 
  small 
  quantities 
  at 
  a 
  time, 
  with 
  frequent 
  stirring, 
  so 
  that 
  several 
  

   hours 
  shall 
  elapse 
  before 
  the 
  last 
  portion 
  is 
  added. 
  The 
  solution 
  is 
  always 
  

   slightly 
  turbid 
  when 
  viewed 
  by 
  reflected 
  light, 
  by 
  which 
  it 
  shows 
  a 
  beautiful 
  

   deep 
  green 
  color. 
  By 
  transmitted 
  light 
  it 
  is 
  deep 
  red, 
  nnd 
  when 
  diluted, 
  abso- 
  

   lutely 
  transparent. 
  By 
  diminishing 
  the 
  proportion 
  of 
  silver 
  nitrate 
  to 
  one-half, 
  a 
  

   solution 
  nearly 
  ©r 
  quite 
  clear 
  by 
  reflected 
  as 
  well 
  as 
  by 
  transmitted 
  light 
  is 
  ob- 
  

   tained. 
  

  

  