﻿410 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  high, 
  if 
  below 
  5$ 
  it 
  is 
  considered 
  very 
  low. 
  Mr 
  Kichardson 
  con- 
  

   eiders 
  that 
  over 
  3^ 
  of 
  magnesia 
  is 
  an 
  excessive 
  and 
  undesirable 
  

   quantity, 
  and 
  the 
  proper 
  limit 
  for 
  sulfuric 
  acid 
  is 
  1 
  J#. 
  The 
  follow- 
  

   ing 
  are 
  the 
  percentages 
  of 
  magnesia 
  and 
  sulfuric 
  acid 
  in 
  portland 
  

   cements 
  which 
  have 
  been 
  placed 
  on 
  American 
  markets 
  during 
  

   the 
  past 
  few 
  years. 
  

  

  MgO 
  SO 
  s 
  

  

  .86 
  1.25 
  

  

  2.79 
  1.71 
  

  

  1.81 
  1.24 
  

  

  1.45 
  1.1 
  

  

  1.68 
  1.50 
  

  

  2.48 
  1.36 
  

  

  2.84 
  1.53 
  

   1.16 
  . 
  2.71 
  

   2.73 
  1.51 
  

  

  1.85 
  1.39 
  

   1.32 
  1.32 
  

  

  Specific 
  gravity 
  of 
  portland 
  cement. 
  This 
  is 
  ascertained 
  by 
  deter- 
  

   mining 
  the 
  volume 
  of 
  an 
  oil 
  which 
  does 
  not 
  act 
  on 
  cement, 
  such 
  

   as 
  dry 
  oil 
  of 
  turpentine, 
  displaced 
  by 
  a 
  known 
  weight 
  of 
  cement. 
  

   For 
  rapid 
  work 
  in 
  the 
  determination 
  of 
  the 
  specific 
  gravity 
  of 
  

   cement 
  a 
  form 
  of 
  volumenometer 
  has 
  been 
  devised 
  (Min. 
  Ind. 
  

   1896, 
  5 
  p. 
  81) 
  which 
  is 
  considered 
  to 
  be 
  free 
  of 
  most 
  of 
  the 
  de- 
  

   fects 
  found 
  in 
  those 
  generally 
  used. 
  It 
  consists 
  of 
  a 
  small 
  flask 
  

   with 
  a 
  short 
  slender 
  graduated 
  neck; 
  the 
  lowest 
  graduation 
  

   mark 
  on 
  the 
  neck 
  is 
  14 
  c. 
  c. 
  and 
  the 
  capacity 
  of 
  the 
  flask 
  is 
  known 
  

   and 
  equals 
  64 
  c. 
  c. 
  The 
  instrument 
  is 
  used 
  by 
  running 
  into 
  it 
  

   a 
  50 
  c. 
  c. 
  oil 
  of 
  turpentine 
  from 
  a 
  pipette 
  which 
  has 
  been 
  accur- 
  

   ately 
  calibrated 
  against 
  the 
  flask. 
  As 
  the 
  oil 
  of 
  turpentine 
  is 
  

   introduced 
  by 
  the 
  pipette 
  the 
  neck 
  of 
  the 
  apparatus 
  is 
  kept 
  dry 
  

   and 
  the 
  known 
  weight 
  of 
  cement, 
  viz 
  50 
  gm 
  can 
  be 
  readily 
  

   added 
  through 
  a 
  small 
  funnel 
  without 
  blocking 
  the 
  tube. 
  The 
  

   shortness 
  of 
  the 
  neck 
  conduces 
  to 
  the 
  easy 
  introduction 
  of 
  the 
  

   cement. 
  The 
  plan 
  of 
  first 
  placing 
  the 
  known 
  weight 
  of 
  cement 
  

   in 
  the 
  flask 
  and 
  then 
  running 
  in 
  50 
  c. 
  c. 
  of 
  oil 
  appears 
  at 
  first 
  

  

  