Keiser & Forder — Determination of Free Lime. 171 



Hydraulic Weight Wt. of Water Per Cent of Per Cent of 

 Compound, properties, taken. taken up. Water. Lime. 



CaOSlOj None. .4829 .0004 .082 .26 



2(CaO)Si02 Not quite as .3988 .0017 '43 1.33 



bard as cement 



.3997 

 2il(CaO)Si02 ditto .4241 



3(CaO)Si02 Hard as cement .4341 

 4fCaO)Si02 None .4241 



We conclude from these results that lime in combination 

 with silica in quantities not exceeding three molecules of lime 

 for one molecule of silica is only slowly acted upon by water 

 and that this method of determining lime can be used to 

 determine free lime in the presence of the basic di- and tri- 

 calcium silicates that are assumed to be present in Portland 

 cements. 



HYDRATION OF CALCIUM ALUMINATE8. 



The mono, di, and tricalcium aluminates were also prepared 

 synthetically by fusing molecular quantities of pure alumina 

 and lime with the oxy-coal gas blowpipe flame. The alumina 

 was prepared by heating the hydroxide that had been ob- 

 tained by precipitation from the chloride by ammonia. The 

 aluminates all fused much more easily than the silicates under 

 the oxy-coal gas blowpipe. Weighed quantities were hydrated 

 by our method as in the case of the silicates and the hydraulic 

 properties were also noted. It was found that the aluminates 

 differ markedly from the sihcates in their behavior towards 

 water. This is shown by the following results : — 



Hydraulic Weight Wt. of Water Per Cent Per Cent 



Compound. properties. taken. taken up. of Water, of Lime. 



(CaOAljOg Set very hard, .4886 .0652 13.34 41.52 



2(CaO)Al203 like a cement .4543 .0716 15.76 49.04 



3(CaO)Al203 None. .4072 .0796 19.55 eoiso 



We see from this that the aluminates are hydrated very 

 much more rapidly than the silicates, in fact they behave 

 like free lime when warmed with . water to 85 degrees for 30 



