XIII, A, 4 Witt and Reyes: Solubility of Portland Cement 155 



Table VII shows that from 87 to 92 per cent of the calcium 

 in a cement will go into solution in twenty-four hours, provided 

 the volume of water present is sufficiently large. Further it 

 seems probable that all of the calcium would dissolve if a still 

 greater volume were used, providing the cement were sufficiently 

 fine and the last trace of carbon dioxide had been removed both 

 from the cement and from the water. We can now see why 

 such results as those of Hart " are misleading. Both the potas- 

 sium and the sulphate ion may be found in solution, but, in place 

 of being the chief constituent, they are negligible in quantity 

 as compared with the calcium. 



On plotting the percentage calcium dissolved against the vol- 

 ume of water present for each cement in Table VII, it may be 



Liters of water. 

































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V 



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Fig. 1. Percentage of calcium dissolved in relation to volume of water present. In order 

 to facilitate comparison, curve II is drawn 10 points above its true position; 

 III, 20 points ; and IV, 30 points. 



seen that the curves agree very closely (fig. 1). This is some- 

 what surprising in that all the cements are of different manu- 

 facture. It will be noted on comparing Tables III and VII that 

 the two cements having the highest percentage of calcium in 

 solution are lowest in calcium. There seems to be no relation 

 between the percentage solubility and the amounts of other 

 constituents present. 



INTERPRETATION OF THE RESULTS IN TERMS OF VARIOUS THEORIES 

 OF HYDRATION 



Unquestionably the most important recent advances in our 

 knowledge of the constitution of cement have been accomplished 



Loc. cit. 



