﻿Chemistry 
  and 
  Physics. 
  439 
  

  

  The 
  equation 
  for 
  the 
  volumetric 
  titration 
  is 
  given 
  as 
  

  

  HgZn(SCN) 
  4 
  + 
  6KI0 
  3 
  + 
  12HC1 
  = 
  HgS0 
  4 
  + 
  ZnS0 
  4 
  + 
  

   2H 
  2 
  S0 
  4 
  + 
  4HCN 
  + 
  6IC1 
  + 
  6KC1 
  + 
  2H 
  2 
  0. 
  

  

  For 
  further 
  details 
  of 
  the 
  processes 
  the 
  original 
  article 
  should 
  

   be 
  consulted, 
  but 
  it 
  may 
  be 
  mentioned 
  that 
  the 
  test 
  analyses 
  gave 
  

   excellent 
  results, 
  and 
  that 
  the 
  method 
  was 
  applied 
  to 
  the 
  exami- 
  

   nation 
  of 
  antiseptic 
  tablets 
  and 
  other 
  commercial 
  preparations 
  

   of 
  mercury. 
  — 
  Jour. 
  Indust. 
  and 
  Eng. 
  Chem., 
  11, 
  296 
  

  

  h. 
  l. 
  w. 
  

  

  2. 
  Chemical 
  Calculations; 
  by 
  R. 
  Harman 
  Ashley. 
  12mo, 
  

   pp. 
  276. 
  New 
  York, 
  1918 
  (D. 
  Van 
  Nostrand 
  Company). 
  —This 
  

   is 
  the 
  second 
  edition 
  of 
  the 
  work, 
  appearing 
  only 
  about 
  four 
  years 
  

   after 
  the 
  original 
  issue, 
  with 
  no 
  changes 
  except 
  some 
  slight 
  

   modifications 
  and 
  corrections. 
  

  

  The 
  problems 
  presented 
  are 
  very 
  numerous 
  and 
  varied, 
  dealing 
  

   with 
  ratios, 
  approximate 
  numbers, 
  interpolation, 
  heat, 
  specific 
  

   gravity, 
  gases, 
  atomic 
  weights, 
  formulas, 
  gravimetric 
  analysis, 
  

   volumetric 
  analysis, 
  and 
  acid 
  specific 
  gravity 
  tables. 
  In 
  general, 
  

   the 
  methods 
  of 
  calculation 
  are 
  very 
  fully 
  and 
  clearly 
  explained. 
  

   Some 
  of 
  the 
  problems 
  may 
  be 
  regarded 
  as 
  rather 
  complex 
  and 
  

   difficult, 
  but 
  there 
  is 
  an 
  amply 
  supply 
  of 
  simpler 
  ones. 
  

  

  The 
  author 
  adopts 
  the 
  method 
  of 
  ratios 
  in 
  preference 
  to 
  the 
  

   use 
  of 
  proportion, 
  and 
  he 
  treats 
  this 
  topic 
  of 
  ratios 
  quite 
  elabo- 
  

   rately; 
  but 
  while 
  it 
  must 
  be 
  said 
  in 
  justice 
  to 
  the 
  author 
  that 
  

   his 
  explanations 
  are 
  usually 
  reliable, 
  it 
  is 
  a 
  curious 
  circumstance 
  

   that 
  he 
  makes 
  a 
  mistake 
  in 
  the 
  statement 
  of 
  his 
  reasoning 
  in 
  his 
  

   very 
  first 
  problem, 
  thus 
  illustrating 
  possibilities 
  for 
  mistakes 
  in 
  

   the 
  ratio 
  method 
  of 
  calculation. 
  At 
  the 
  bottom 
  of 
  page 
  2 
  he 
  

   says 
  " 
  . 
  . 
  . 
  one 
  part 
  by 
  weight 
  of 
  oxygen 
  [in 
  HgO] 
  is 
  given 
  

  

  by 
  , 
  , 
  parts 
  of 
  mercuric 
  oxide 
  . 
  . 
  .," 
  whereas 
  it 
  is 
  one 
  

  

  part 
  of 
  mercuric 
  oxide 
  that 
  gives 
  this 
  amount 
  of 
  oxygen. 
  How- 
  

   ever, 
  the 
  problem 
  is 
  solved 
  correctly 
  in 
  spite 
  of 
  the 
  faulty 
  state- 
  

   ment. 
  

  

  The 
  chapter 
  on 
  approximate 
  numbers 
  deserves 
  severe 
  criticism, 
  

   for 
  the 
  author 
  evidently 
  does 
  not 
  fully 
  understand 
  this 
  subject. 
  

   He 
  states 
  on 
  page 
  29 
  that 
  assuming 
  no 
  errors 
  in 
  the 
  numbers, 
  

  

  "1-862 
  X 
  0-6257 
  = 
  1-1650534", 
  

  

  where 
  the 
  line 
  under 
  the 
  figure 
  indicates 
  that 
  it 
  is 
  uncertain. 
  

   Of 
  course, 
  if 
  the 
  numbers 
  multiplied 
  are 
  exact 
  ones 
  all 
  the 
  

   figures 
  in 
  the 
  result 
  must 
  be 
  exact 
  also, 
  and 
  even 
  assuming 
  

   "maximum 
  apparent 
  errors," 
  which 
  the 
  author 
  is 
  discussing, 
  in 
  

   these 
  data 
  the 
  result 
  would 
  be 
  11651. 
  

  

  ±3 
  

   The 
  author 
  usually 
  carries 
  out 
  the 
  decimals 
  in 
  the 
  answers 
  to 
  

   the 
  problems 
  to 
  a 
  reasonable 
  extent, 
  but 
  a 
  few 
  answers 
  are 
  car- 
  

  

  Am. 
  Jour. 
  Sci.— 
  Fourth 
  Series, 
  Vol. 
  XLVII, 
  No. 
  282.— 
  June, 
  1918. 
  

   30 
  

  

  