﻿Chemistry 
  and 
  Physics. 
  299 
  

  

  corresponding 
  nearly 
  to 
  the 
  composition 
  required 
  by 
  the 
  formula 
  

   Mg 
  2 
  Sn, 
  then 
  pulverizing 
  it 
  and 
  treating 
  it 
  with 
  hydrochloric 
  or 
  

   sulphuric 
  acid, 
  usually 
  of 
  about 
  4-normal 
  strength 
  in 
  an 
  appa- 
  

   ratus 
  similar 
  to 
  that 
  used 
  in 
  the 
  Marsh 
  test 
  for 
  arsenic. 
  The 
  

   hydrogen 
  thus 
  produced 
  gave 
  metallic 
  mirrors 
  of 
  tin 
  in 
  the 
  

   heated 
  tube. 
  The 
  yield 
  was 
  exceedingly 
  small 
  in 
  proportion 
  to 
  

   the 
  amount 
  of 
  alloy 
  employed, 
  but 
  there 
  appears 
  to 
  be 
  no 
  doubt, 
  

   from 
  the 
  account 
  of 
  the 
  tests 
  made 
  upon 
  the 
  mirrors, 
  that 
  a 
  

   gaseous 
  tin 
  hydride 
  has 
  at 
  last 
  been 
  prepared. 
  Experiments 
  

   showed 
  that 
  the 
  substance 
  could 
  be 
  condensed 
  by 
  passing 
  the 
  

   hydrogen 
  containing 
  it 
  through 
  a 
  U-tube 
  cooled 
  with 
  liquid 
  air, 
  

   but 
  no 
  sufficient 
  quantity 
  of 
  it 
  had 
  as 
  yet 
  been 
  prepared 
  for 
  the 
  

   determination 
  of 
  its 
  physical 
  properties 
  or 
  its 
  chemical 
  formula. 
  

   It 
  may 
  be 
  observed 
  that 
  the 
  same 
  authors 
  have 
  recently 
  shown 
  

   in 
  a 
  similar 
  way 
  the 
  existence 
  of 
  hydrides 
  of 
  bismuth 
  and 
  its 
  

   radioactive 
  isotope 
  polonium, 
  and 
  that 
  they 
  have 
  announced 
  the 
  

   probable 
  existence 
  of 
  a 
  gaseous 
  hydride 
  of 
  lead. 
  — 
  Berichte, 
  52, 
  

   2020. 
  h. 
  l. 
  w. 
  

  

  3. 
  A 
  New 
  Indicator 
  for 
  Bases 
  and 
  Acids. 
  — 
  It 
  is 
  stated 
  by 
  

   M. 
  Chauveerre 
  that 
  the 
  coloring 
  matter 
  of 
  red 
  beets 
  is 
  an 
  

   exceedingly 
  delicate 
  reagent 
  for 
  the 
  detection 
  of 
  bases 
  and 
  acids. 
  

   To 
  prepare 
  the 
  indicator 
  some 
  pieces 
  of 
  beet 
  are 
  boiled 
  with 
  

   water 
  and 
  the 
  solution 
  is 
  filtered. 
  A 
  very 
  opalescent 
  liquid 
  of 
  

   a 
  beautiful 
  violet-red 
  color 
  is 
  thus 
  obtained 
  to 
  which 
  a 
  drop 
  of 
  

   potassium 
  hydroxide 
  solution 
  gives 
  a 
  bright 
  yellow 
  color. 
  This 
  

   yellow 
  liquid 
  is 
  a 
  reagent 
  of 
  great 
  delicacy 
  for 
  acids, 
  and 
  not 
  

   only 
  mineral 
  acids 
  but 
  also 
  the 
  weakest 
  organic 
  acids, 
  such 
  as 
  

   tartaric 
  acid 
  and 
  oxalic 
  acid, 
  produces 
  the 
  original 
  violet-red 
  

   color. 
  It 
  is 
  stated 
  that 
  the 
  reagent 
  is 
  much 
  more 
  sensitive 
  than 
  

   litmus 
  or 
  even 
  phenolphthalein, 
  but 
  it 
  cannot 
  be 
  used 
  in 
  the 
  

   form 
  of 
  a 
  test-paper, 
  since 
  the 
  coloring 
  matter 
  is 
  not 
  fixed 
  by 
  

   paper. 
  It 
  appears 
  that 
  this 
  coloring 
  matter 
  does 
  not 
  form 
  a 
  

   true 
  solution, 
  but 
  is 
  colloidal 
  in 
  its 
  nature, 
  as 
  is 
  indicated 
  by 
  its 
  

   opalescent 
  character. 
  It 
  is 
  stated 
  that 
  the 
  reagent 
  is 
  sensitive 
  

   to 
  dilute 
  boric 
  acid 
  solution, 
  but 
  no 
  statement 
  is 
  made 
  in 
  regard 
  

   to 
  its 
  behavior 
  with 
  carbon 
  dioxide, 
  a 
  matter 
  of 
  much 
  importance 
  

   in 
  connection 
  with 
  its 
  practical 
  application. 
  — 
  Bull. 
  Soc. 
  Chem., 
  

   25, 
  118. 
  h. 
  l. 
  w. 
  

  

  4. 
  Chemically 
  Reactive 
  Alloys. 
  — 
  E. 
  A. 
  Ashcroft 
  calls 
  atten- 
  

   tion 
  to 
  certain 
  alloys 
  that 
  are 
  oxidized 
  with 
  remarkable 
  rapidity 
  

   by 
  cold, 
  moist 
  air. 
  Alloys 
  of 
  calcium 
  and 
  lead 
  show 
  this 
  

   behavior 
  to 
  a 
  considerable 
  degree, 
  but 
  they 
  are 
  not 
  so 
  rapidly 
  

   oxidized 
  as 
  magnesium-lead 
  alloys. 
  This 
  behavior 
  was 
  ob- 
  

   served 
  when 
  from 
  5 
  to 
  50 
  per 
  cent, 
  of 
  magnesium 
  was 
  present, 
  

   but 
  it 
  appears 
  that 
  a 
  mixture 
  of 
  15% 
  magnesium 
  and 
  85% 
  lead 
  

   produces 
  one 
  of 
  the 
  most 
  active 
  alloys. 
  Moisture 
  is 
  essential 
  to 
  

   the 
  reaction, 
  the 
  crushed 
  alloy 
  is 
  most 
  rapidly 
  attacked, 
  but 
  

   large 
  pieces 
  are 
  quickly 
  oxidized 
  and 
  fall 
  to 
  powder. 
  The 
  prod- 
  

  

  