﻿of 
  the 
  Atomic 
  Weights 
  of 
  Elementary 
  Substances. 
  733 
  

  

  within 
  small 
  fractional 
  quantities, 
  the 
  atomic 
  weight 
  and 
  

   correlated 
  specific 
  heat 
  of 
  silicon 
  are 
  still 
  open 
  to 
  revision, 
  

   notwithstanding 
  the 
  large 
  amount 
  of 
  attention 
  which 
  has 
  

   been 
  given 
  by 
  chemists 
  to 
  determine 
  these 
  constants 
  of 
  

   nature. 
  

  

  In 
  order 
  that 
  the 
  connexion 
  between 
  the 
  results 
  of 
  the 
  

   present 
  paper 
  with 
  my 
  former 
  researches 
  may 
  be 
  seen 
  without 
  

   the 
  trouble 
  of 
  references, 
  I 
  will 
  recapitulate 
  several 
  of 
  the 
  

   points 
  previously 
  discussed, 
  together 
  with 
  the 
  explanatory 
  

   tables 
  of 
  atomic 
  weights. 
  

  

  Since 
  the 
  investigation 
  of 
  the 
  properties 
  of 
  silicon 
  by 
  

   Berzelius, 
  who 
  regarded 
  silicic 
  acid 
  as 
  a 
  trioxide, 
  much 
  dis- 
  

   cussion 
  has 
  arisen 
  as 
  to 
  whether 
  the 
  atomic 
  weight 
  of 
  silicon 
  

   should 
  be 
  21, 
  28, 
  or 
  35, 
  and 
  the 
  formula 
  for 
  its 
  oxide 
  Si 
  2 
  3 
  , 
  

   Si0 
  2 
  , 
  or 
  Si 
  2 
  O 
  r 
  ,. 
  

  

  Through 
  the 
  classical 
  researches 
  of 
  Regnault 
  the 
  specific 
  

   heat 
  of 
  silicon 
  was 
  found 
  to 
  be 
  0*176*. 
  The 
  determination 
  

   was 
  made 
  with 
  specimens 
  of 
  the 
  metalloid 
  of 
  considerable 
  

   size 
  and 
  in 
  a 
  state 
  of 
  compactness 
  and 
  purity 
  to 
  receive 
  a 
  

   polish 
  which 
  formed 
  a 
  perfect 
  mirror. 
  The 
  above 
  number 
  

   multiplied 
  by 
  28, 
  the 
  highest 
  atomic 
  weight 
  assigned 
  to 
  Si, 
  

   gives 
  the 
  product 
  4*93, 
  while 
  the 
  law 
  of 
  Dulong 
  and 
  Petit 
  

   requires 
  the 
  value 
  6*25. 
  

  

  In 
  discussing 
  the 
  cause 
  of 
  the 
  anomalous 
  atomic 
  heat 
  of 
  

   silicon, 
  Regnault 
  pointed 
  out 
  that 
  in 
  order 
  that 
  it 
  might 
  

   enter 
  into 
  the 
  law 
  of 
  the 
  specific 
  heat 
  of 
  other 
  elements, 
  it 
  

   would 
  be 
  necessary 
  to 
  write 
  the 
  formula 
  of 
  silicic 
  acid 
  

   Si 
  2 
  5 
  ; 
  it 
  would 
  then 
  resemble 
  that 
  of 
  nitric, 
  phosphoric, 
  and 
  

   arsenic 
  acid. 
  The 
  atomic 
  weight 
  of 
  silicon 
  would 
  then 
  be 
  

   35, 
  and 
  the 
  product 
  of 
  this 
  number 
  and 
  the 
  specific 
  heat 
  

   would 
  be 
  nearly 
  6*25, 
  which 
  agrees 
  with 
  the 
  analogous 
  pro- 
  

   ducts 
  that 
  other 
  simple 
  bodies 
  give. 
  By 
  assigning 
  to 
  silicon 
  

   a 
  higher 
  atomic 
  weight 
  and 
  a 
  polybasic 
  character 
  like 
  that 
  

   of 
  phosphorus 
  or 
  nitrogen, 
  Regnault 
  remarked 
  that 
  it 
  is 
  

   easy 
  to 
  explain 
  the 
  existence 
  of 
  the 
  great 
  number 
  of 
  silicates 
  

   which 
  nature 
  presents 
  in 
  well-defined 
  and 
  beautiful 
  crystals, 
  

   and 
  to 
  understand 
  the 
  existence 
  of 
  the 
  natural 
  hydro- 
  

   silicates. 
  

  

  It 
  will 
  be 
  seen 
  from 
  my 
  general 
  Table 
  that 
  the 
  atomic 
  

   weights 
  of 
  nitrogen, 
  silicon, 
  and 
  iron, 
  besides 
  being 
  whole 
  

   numbers, 
  are 
  exact 
  multiples 
  of 
  H7 
  ; 
  and 
  in 
  all 
  the 
  formulas 
  

   proposed 
  for 
  the 
  constitution 
  of 
  silica 
  the 
  atomic 
  weight 
  of 
  

   silicon 
  is 
  a 
  multiple 
  of 
  7. 
  These 
  formulas 
  are 
  given 
  below, 
  

  

  * 
  Annates 
  de 
  Chemie 
  et 
  de 
  Physique, 
  liii. 
  pp. 
  24-31 
  (1861) 
  

  

  