﻿438 
  Scientific 
  Intelligence. 
  

  

  Length 
  bottom 
  line 
  of 
  centrum, 
  first 
  dorsal 
  .... 
  39 
  

  

  Length 
  bottom 
  line 
  of 
  centrum, 
  eighth 
  cervical 
  . 
  36-6 
  

  

  Length 
  bottom 
  line 
  of 
  centrum, 
  seventh 
  cervical 
  39-2 
  

  

  Length 
  bottom 
  line 
  of 
  centrum, 
  sixth 
  cervical 
  . 
  . 
  49-5 
  

  

  Length 
  bottom 
  line 
  of 
  centrum, 
  fifth 
  cervical 
  . 
  . 
  . 
  51-6 
  

  

  University 
  of 
  Michigan, 
  

   Ann 
  Arbor, 
  Mich. 
  

  

  SCIENTIFIC 
  INTELLIGENCE. 
  

   I. 
  Chemistry 
  and 
  Physics. 
  

  

  1. 
  The 
  Gravimetric 
  and 
  Volumetric 
  Determination 
  of 
  Mer- 
  

   cury 
  Precipitated 
  as 
  Mercury 
  Zinc 
  Thiocyanate. 
  — 
  George 
  S. 
  

   Jamieson, 
  of 
  the 
  Bureau 
  of 
  Chemistry, 
  Department 
  of 
  Agricul- 
  

   ture, 
  Washington, 
  D. 
  C, 
  has 
  devised 
  a 
  method 
  for 
  precipitating 
  

   mercury 
  from 
  solutions 
  containing 
  the 
  metal 
  in 
  the 
  mercuric 
  con- 
  

   dition 
  by 
  producing 
  the 
  double 
  salt 
  HgZn(SCN) 
  4 
  and 
  either 
  

   weighing 
  this 
  salt 
  or 
  titrating 
  it 
  by 
  means 
  of 
  potassium 
  iodate 
  

   solution 
  in 
  the 
  presence 
  of 
  strong 
  hydrochloric 
  acid 
  with 
  the 
  use 
  

   of 
  a 
  little 
  chloroform 
  as 
  an 
  indicator. 
  In 
  order 
  to 
  get 
  a 
  quanti- 
  

   tative 
  precipitation 
  of 
  the 
  mercury 
  in 
  this 
  form 
  there 
  should 
  not 
  

   be 
  more 
  than 
  5 
  per 
  cent 
  of 
  acid 
  present 
  in 
  the 
  liquid 
  before 
  the 
  

   addition 
  of 
  the 
  reagent, 
  which 
  contains 
  29 
  g. 
  of 
  zinc 
  sulphate 
  

   and 
  39 
  g. 
  of 
  ammonium 
  thiocyanate 
  per 
  liter. 
  In 
  case 
  that 
  it 
  is 
  

   necessary 
  to 
  neutralize 
  an 
  excess 
  of 
  acid, 
  sodium 
  hydroxide 
  

   rather 
  than 
  ammonia 
  should 
  be 
  used, 
  as 
  large 
  amounts 
  of 
  ammo- 
  

   nium 
  salts 
  increase 
  the 
  solubility 
  of 
  the 
  precipitate. 
  It 
  was 
  

   found 
  that 
  copper, 
  cobalt, 
  bismuth 
  and 
  nickel 
  are 
  partially 
  pre- 
  

   cipitated 
  along 
  with 
  the 
  mercuric 
  zinc 
  thiocyanate, 
  hence 
  if 
  pres- 
  

   ent 
  they 
  would 
  interfere 
  with 
  this 
  method 
  of 
  determination. 
  

   The 
  reviewer 
  makes 
  the 
  suggestion 
  here 
  that 
  if 
  the 
  copper, 
  cobalt 
  

   and 
  nickel 
  merely 
  replace 
  zinc 
  isomorphously 
  in 
  the 
  precipitate 
  

   they 
  should 
  not 
  interfere 
  with 
  the 
  volumetric 
  determination, 
  

   since 
  in 
  that 
  case 
  they 
  would 
  not 
  by 
  their 
  presence 
  change 
  the 
  

   proportion 
  of 
  mercury 
  to 
  thiocyanogen. 
  

  

  For 
  the 
  gravimetric 
  operation 
  the 
  precipitate 
  is 
  collected 
  on 
  a 
  

   Gooch 
  crucible 
  and 
  washed 
  with 
  small 
  quantities 
  of 
  a 
  solution 
  

   containing 
  5 
  cc. 
  of 
  the 
  precipitating 
  reagent 
  and 
  450 
  cc. 
  of 
  water, 
  

   because 
  the 
  precipitate 
  is 
  appreciably 
  soluble 
  in 
  pure 
  water. 
  

   Drying 
  at 
  102 
  to 
  108 
  is 
  recommended 
  before 
  weighing. 
  

  

  For 
  the 
  volumetric 
  process 
  the 
  precipitate 
  was 
  collected 
  on 
  

   small 
  filter-papers, 
  washed 
  at 
  first 
  with 
  a 
  mixture 
  of 
  10 
  cc. 
  of 
  

   the 
  precipitating 
  reagent 
  and 
  450 
  cc. 
  of 
  water, 
  then 
  with 
  small 
  

   quantities 
  of 
  the 
  previously 
  mentioned 
  weaker 
  mixture. 
  

  

  