xm, A. 4 Witt and Reyes: Solubility of Portland Cement 153 



first period — about double. The time necessary for completion 

 was shorter, and the percentage of the total calcium present 

 was higher. 



The total amounts of other elements in solution are negligible 

 in comparison with the calcium. The complete analysis of the 

 liquid after twenty-four hours of shaking is shown in Table V. 

 The first column under each number shows the amount of each 

 constituent dissolved per gram of cement. The second column 

 shows the percentage of the total amount of each constituent 

 in solution (compare with Table III). 



Table V. — The weight of each constituent (per gram of cement) that goes 

 into solution during the first twenty-four hours. Also the percentage 

 of the total amount of each constituent present that is dissolved. 





Brand. 



I. 



II. 



III. 



1 

 IV. 1 



Silica (SiOz) 



a- 

 trace 



0.0088 

 0. 1797 

 trace 



0.0045 

 0.0131 



P.ct. 



8.64 

 29.39 



42.06 

 66.50 



g. 

 trace 



0.0065 

 0. 1998 

 trace 



0.0041 

 0. 0183 



P.ct. 



7.00 

 32.03 



64.06 

 75.31 



g. 

 trace 



0.0037 

 0.2135 

 trace 



0.0044 

 0.0111 



P.ct. 



3.11 

 34.61 



69.84 

 68.62 



g. 

 trace 



0.0064 

 0.2147 

 trace 



0.0067 

 0.0096 



P.ct. 



6.82 

 34.62 



65.52 

 75.59 



Iron and aluminium oxides 

 (Fe203, AlzOa) 





Magnesium oxide (MgO) 



Sodium and potassium oxides 

 (Na20, K2O) 



Sulphuric anhydride (SO3) 



There is no important increase in the amounts of these consti- 

 tuents in solution after the first period of shaking. The per- 

 centage of each constituent in solution is interesting. We should 

 not expect to find any soluble silicates under these conditions, 

 and the small amount of iron, aluminium and magnesium in 

 solution is not surprising when such a large concentration of 

 calcium hydroxide is present. The absence of magnesium may 

 be partly due to the slowness with which magnesium compounds 

 hydrate. The slight solubility of calcium sulphaluminate ex- 

 plains the small amount found in solution. 



After the series of experiments had reached completion, and 

 no further calcium went into solution, the precipitate remaining 

 in each flask was collected and washed. (It was not possible to 

 wash completely free from soluble calcium compounds.) The 

 residues were then analyzed as a check on the analyses of the 

 soluble portion. In Table VI the first line shows the loss on 

 ignition, after the material had been dried to constant weight at 

 110° C. The other results were calculated to the after-ignition 

 basis, in order that they might be more comparable with the 

 cement before water was added. 



