MgO content

Figure 1.138. MgO content variation for underground samples. Diamond Yusen No. 7 vein square Seisen No. 8 vein.

K2O and MgO contents of altered andesite decreases away from the vein (Fig. 1.137BandFig. 1.138). 

Although data are scattered and mostly no systematic correlation of Na20, CaO and MgO contents with 5 0 exist, K2O content and S O seem negatively correlated K2O content is low and high for zone 1 and IV and S 0 is high and low for zone 1 and IV, respectively. 

The Mg content of hydrothermally altered volcanic rocks is reflected by the extent of seawater-volcanic rock interaction at elevated temperatures, because it has been experimentally and thermodynamically determined that nearly all of the Mg in seawater transfer to volcanic rocks, owing to the reaction of the cycled seawater with volcanic rocks at elevated temperatures (Bischoff and Dickson, 1975 Mottl and Holland, 1978 Wolery, 1979 Hajash and Chandler, 1981 Reed, 1983 Seyfried, 1987). It has been shown that the CaO content of hydrothermally altered midoceanic ridge basalt is inversely correlated with the MgO content with a slope of approximately — 1 on a molar basis (Mottl, 1983). This indicates that Ca of basalt is removed to seawater and Mg is taken up from seawater by the formation of chlorite and smectite during the seawater-basalt interaction. This type of reaction is simply written as ... 

Figure 13. Effect of diffusivity and MgO content on p-xylene selectivity. Toluene disproportionation at 550 C, 20% conversion o-xylene diffusion time at 120°C.

Table IV. Effect of MgO Content on the Properties of MgO-Modified HZSM-5 Catalysts...

Figure 14. Effect of MgO content on the activity of MgO-HZSM-5 catalysts. Toluene conversion at 577°c,...

A basaltic liquid with an FeO content C0FeO of 10 percent and an MgO content C0M8° of 12 percent crystallizes olivine (ol). Calculate the FeO and MgO contents CHqFe° and CliqMg° after 15 percent crystallization. 

Figure 4. Plot of Li isotopic composition vs. MgO content for samples of the Kilauea Iki lava lake, Hawaii (Tomascak et al. 1999b). Cored basalt samples show a range of crystallization temperatures (estimated for four of the samples). The absence of permil-level variation in 5 Li indicates that Li isotopes do not fractionate appreciably during crystallization in mantle systems. Open symbols (o) are replicate measurements.

Least-altered metavolcanic samples have Na20 and MgO contents of 1.8-4.0 wt. % and 4-25 wt. %, respectively, whereas strongly altered samples (having greater than 30% hydrothermal minerals by volume, in dense net-textured veins, in places obscuring primary textures) contain less than 1.5 wt. % Na20 and 11-23 wt. % MgO. 

MgO content of the additive is a parameter affecting the SO reduction efficiency. However, for an additive to be effective and stable, the MgO must be integral to the strnctnre of the additive. 

Among the deleterious materials (Fc203, AI2O3, CaO, MgO) in phosphate rock, dolomite is the most troublesome. Dolomite causes higher consumption of sulfuric acids, reduces filtration capacity, and lowers the P2O5 recovery in fertilizer manufacturing. Therefore the MgO content is a very important index in evaluating the quality of the phosphate concentrate, hi Florida, the MgO in the final phosphate concentrate is usually required to be less than 1%. 

Similarly, the MgO content of the ashes is largely derived from thermal decomposition of magnesian carbonates. This process also expels water from hydrated minerals present in the oil shale. The Fe-sulphide content of the original shales is oxidized to ferric oxides and sulphates in the ash (expressed as S03 in Table 4). 

The alkaline mafic volcanics are less enriched in silica and more enriched in incompatible trace elements than oversaturated tholeiitic rocks with similar MgO contents. REE show smooth and fractionated patterns (Fig. 9.7). Mantle normalised incompatible element patterns of mafic rocks generally display a small upward convexity with moderate enrichments in Ta and Nb. The large majority of the mafic volcanic rocks exhibit positive spikes of Ba and Pb, which are small or absent in the southern outcrops of Capo Ferrato, Guspini and Rio Girone (Fig. 9.7). Silicic volcanics exhibit a large range of incompatible element concentrations. Sr- and Nd-isotopic... 

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). 

The chemical composition of the support affects the course of the beginning of coking and the length of the induction period. The influence of MgO content in the support of Ni/cc-AljC + MgO catalysts (catalysts of series B) on the weight of carbon and the length of the induction period is presented in Figure 2. 

Figure 5 presents the influence of MgO content on relative coking rates (rj/r2) where rj denotes the coking rate without, and r2 the coking rate with, the initiation process, respectively. 

Figure 5 Influence of MgO content in the support on the relative coking rate of catalysts after various kinds of pretreatment.

The length of the induction period is affected by all the same factors which affect the coking rate of nickel catalysts in the steam reforming of hydrocarbons. A high dispersion of nickel, an increase in MgO content in the support or a small additive of a promoter all cause a prolongation of the induction time. 

Clinker belites typically contain 4-6% of impurity oxides, of which the chief ones are usually AI2O3 and Fe203. Correlations have been reported to exist between the MgO contents of belite and clinker (Kl), the Fe20, contents of belite and clinker (Kl), and the total impurity content of the belite and the MgO content of the clinker (B4). Early reports mention a compound KC23S,2, but the K2O content of 3.5% corresponding to this formula is well above those found in clinker belites, and recent electron optical work indicates that the limit of K2O substitution is about 1.2% (C1). 

All the effects described above indicate that rapid cooling is desirable the aluminate phase reacts more slowly with water when finely grained and intimately mixed with ferrite, making it easier to control the setting rate (S24), decrease in alite content either from reactions involving the interstitial material or from decomposition is avoided, a higher MgO content can be tolerated, and the clinker is easier to grind. 

The pumping time is very sensitive to MgO content in the Ceramicrete slurry. A slight increase in MgO accelerates the acid-base reaction, and the slurry sets faster. Figure 15.5 shows the effect of excess MgO on the pumping time at 200 °F (93°C). Excess MgO provides additional surface area for dissolution. It also provides additional nucleation sites... 

FIGURE 5.1. Relationship between the Si02 and MgO contents of igneous rocks. 

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