Keiser & Forder — Determination of Free Lime. 173 



to 85 degrees for 30 minutes. Then the temperature was 

 raised to 185 degrees and a slow current of air drawn through 

 until constant weight was obtained. The following results 

 were obtained : — 



These cements all gave good * * sound ' ' tests and in nearly 

 all cases less than 3 per cent of water was taken up. We 

 conclude from this and from the preceding experiments 

 upon cements that this water was taken up by the aluminates 

 and that little or no free lime was contained in these cements. 

 One variety of Portland cement that we examined gave 10.17 

 per cent of water taken up. We concluded that 7 per cent 

 of this must be due to free lime being present. Our conclu- 

 sion was justified, for on making a pat of the neat cement 

 and allowing it to set thoroughly it was immersed in boiling 

 water, and on removal from the water it showed signs of 

 cracks and had become quite soft and readily disintegrated. 



Two varieties of natural cements were tested and gave the 



Finally we have tested our method by adding weighed 

 amounts of pure lime to a cement of known behavior and 

 then after ignition with the blast lamp have again determined 

 the percentage of water taken up. Thus cement A which 



