Silicate groups

The measured potential is thus a linear function of pH an extremely wide (10-14 decades) linear range is obtained, with calibration plots yielding a slope of 59 mV per pH unit. The overall mechanism of the response is complex. The selective response is attributed to the ion-exchange properties of the glass surface, and in particular the replacement of sodium ions associated with the silicate groups in the glass by protons ... 

Structure Formula of Silicate Group Common Names Si 0 Ratio Examples of Mineral Groups... 

As observed earlier, in modeling the Si—O—Si unit of silica and related silicates, the geometry of the HgSi207 molecule was constrained during its optimization so that the terminating H atoms of each of the silicate groups were directed away from the O atoms of the other group so as to avoid the formation of one or more O- H bonded interactions. If such a constraint is not made, then O- H bonded interactions can be... 

Today, the atomic mechanism that causes the piezoelectric effect is well understood. Quartz, for example, consists of long chains of silicate (Si042-) groups arranged in a helical pattern, as shown in the diagram below. In any one silicate group, the atoms are arranged... 

Figure 8.5 A mechanism for the dissolution and hydrolysis of a ferromagnesian silicate. The figure is a two-dimensional representation of the reaction described in the text ( 8.7.1). Oxygens of two additional silicate groups lie above and below the plane.

Nakayama and Tanaka found that the chlorination of 2-silylfuran 109 with sulfuryl chloride gave the corresponding 2-chloro-3-silylfuran 110 and 2-chlorofuran 111 as shown in equation 75184. 1,2-Migration of a pentacoordinate silicate group was assumed to be involved in this reaction (equation 76). 

More complex, but still discrete silicate groupings have been found to exist in the minerals benitoite and beryl the former, BaTiSi309, contains six-membered silicon-oxygen rings, whereas the latter, BesAUSieOig, contains twelve-membered rings (Fig. 17-3). 

On the other hand, Kumada and Tamao disclosed that an organo(pentaflu-oro)silicate underwent desilylative coupling with iodobenzene in the presence of a palladium catalyst under rather drastic reaction conditions (Eq. 2) [9]. Although the nucleophilicity at the carbon atom having a silicate group is apparently enhanced, a czne-coupling product in addition to an zpso-coupling product is produced. 

Table II. Physico-Chemical Properties of Silicate Groups- -...

Fig. 5.18. The Si L2 3 x-ray emission spectra of various silicates, as shown, and of quartz. In terms of structural silicate groups (1-7) are island silicates, (8-9) ring silicates, (10-U) single-chain silicates, (12-15) double-chain silicates, (16-19) sheet silicatesj (20-22) framework silicates (after Dikov et al., 1976 reproduced with the publisher s permission).

The so-called non-silicate minerals consist of a variety of different mineral groups each named for a particular anion. Only a few of these minerals contribute much volume to Earth s crust, but many of them are very important minerals for manufacturing and other industrial uses. Most mineralogists recognize ten or so major nonsilicate groups and a variable number of lesser groups. Table 2 lists several of the major non-silicate groups. 

In filler applications, the silicates group of greatest interest is in the subclass of tektosilicates. Four minerals (quartz, tridymite, cristobalite, and opal) belong to the silica group and three of them (quartz, cristobalite, and opal) are used as fillers or materials for their production. 

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