In IS 269, Table 2, note 1, it has been prescribed that, the alkali content should be expressed as sodium oxide (Na2O + 0.658 K2O). Kindly clarify the following points:
1. Is the conversion is eqtuivalent weight conversion? And how to convert it in the combination?
2. Why the combination of Na2O and K2O? Is Na2O or K2O alone is sufficient? Kindly provide some details regarding the factor 0.658
The conversion is based in the equivalent molar mass, the ration of Na2O to K2O will be about 0.658.
The alkalies commonly found in cement are either Na or K, so just considering these two should be sufficient.
0.658 is the ratio between the formula weight of Na2O and that of K2O.
Atomic mass of sodium is 23 u
Atomic mass of potassium is 39u
Atomic mass of oxygen is 16u
Na2O =23*2+16=62
K2O=39*2+16=94
K2O/Na2O= 0.658
I am not an expert in such kind of topics. Yet, what I can say is that 0.658 is the numerical factor by which a given mass of K2O has to be multiplied in order to obtain the mass of Na2O corresponding to the same number of moles of K2O. Actually, one mole of K2O is (39.1 X 2 + 16) = 94.2 g, while one mole of Na2O is (23 X 2 + 16) = 62 g. If you multiply 94.2 by 0.658, you obtain 62.
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