NazO content

The type phengite suggested by Foster (1956) has a composition almost identical to that of the Belt illite (No.8). When the H20 content is appreciably higher and the K20 content lower than muscovite, the minerals have been called hydromicas or hydromuscovites. The excess H20 in some instances is present as interlayer water, particularly in the trioctahedral hydrobiotites. Table XII contains a selection of sericite and hydromuscovite analyses and Table XIII the structural formulas. The H20 and K20 values of these minerals are similar to those reported for the illite minerals however, the MgO content of the sericites and hydromuscovites is lower and the NazO contents higher than for the illites (Table XIV). 

Percent linear shrinkage measured during heating at l C/min for a series of borosilicate gels prepared with varying Na20 contents [130]. The region II-III transition increases from about 525 to 750°C as the NazO content is reduced from 6.3 to Owt /o. 

Ash is the product of combustion of mineral matters associated with coal. It consists principally of silica, alumina, and ferric oxide with variable amounts of other oxides such as CaO, MgO, and NazO. A high ash content is in general not desirable. A coal with high ash... 

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