Pyrex-type glasses

In practice, the restrictions emunerated above limit the sheath glass material to one of the low thermal expansion, borosilicate (Pyrex-type) glasses or fused silica. 

Of the three commonly available types of glasses, borosilicate (Pyrex-type) glasses appear to be the most satisfactory. They combine the properties of good electrical resistance, resistance to thermal shock, and mechanical... 

Pyrex-type glasses fit this demands. Na ions provide the electrical conductivity, but the glass also contains small amounts of AI2O3 which prevents the unwanted phase separation (see Sect. 1.1.6). The homogeneous microstructure of a Pyrex glass is shown in Fig. 1.37. 

Fig. 1.37. TEM-micrograph of a Pyrex-type glass [537]. The Mo-oxide crystal partially seen in the top left corner demonstrates the resolution...

Fig. 3.12. Specific electrical resistivity of a Pyrex-type glass (1), Neutral-glass 4.9 (2), alkaline free Alumo-Boro-Silicate glass (3), E-fiber glass (4) and an alkaline poor Alumo-Boro-Silicate glass (5) melt as function of the temperature [486]...

Figure 2 shows the effect of tube i.d. on the measured separation efficiency of dansyl-labelled isoleucine( M) The tubes were all 100 cm long Pyrex type 7740 borosilicate glass capillaries, filled with pH 6.86, 0.05 M phosphate buffer, and operated at a potential of 15 KVolts. Only the tube diameters were varied. Clearly, below 80 microns, a performance of approximately 250,000 theoretical plates is obtained, and no... 

Pyrex type chemically-resistant borosilicate glasses... 

Around 1970, three different groups in the field of inorganic materials published research results on preparation of glass and ceramics via solutions or sol-gel route. H. Dislich prepared a pyrex-type borosilicate glass lens by heating a compact of metal alkoxide derived powder at temperatures as low as 650°C. R. Roy prepared a milhmeter-size small piece of silica glass via sol-gel route at temperatures around 1000°C. Mazdiyasni et al. showed that well-sintered, dense ferroelectric ceramics can be obtained at temperatures as low as 900°C, when sol-gel powders prepared from solutions of metal alkoxides are employed for sintering. 

AU ground glass joints should be constructed of a high resistance glass, such as Pyrex. The most common form is shown in Fig. II, 55, 1, and this is the type largely encountered in practice. Fig. II, 55, 2 is... 

The Stedman-type column is shown in Fig. 11, 56, 25. The characteristic features are (i) the use of a fine stainless steel wire cloth formed into conical discs, and (ii) an accurately fitting Pyrex glass jacket, produced by shrinking Pyrex glass on mandrels to the required inside dimensions. Modifications incorporating a silvered vacuum jacket and an electrically-heated jacket are marketed. This column is said to possess high efficiency but is expensive. It is generally employed in conjunction with a total-condensation variable take-off still head. 

The H-type cell devised by Lingane and Laitinen and shown in Fig. 16.9 will be found satisfactory for many purposes a particular feature is the built-in reference electrode. Usually a saturated calomel electrode is employed, but if the presence of chloride ion is harmful a mercury(I) sulphate electrode (Hg/Hg2 S04 in potassium sulphate solution potential ca + 0.40 volts vs S.C.E.) may be used. It is usually designed to contain 10-50 mL of the sample solution in the left-hand compartment, but it can be constructed to accommodate a smaller volume down to 1 -2 mL. To avoid polarisation of the reference electrode the latter should be made of tubing at least 20 mm in diameter, but the dimensions of the solution compartment can be varied over wide limits. The compartments are separated by a cross-member filled with a 4 per cent agar-saturated potassium chloride gel, which is held in position by a medium-porosity sintered Pyrex glass disc (diameter at least 10 mm) placed as near the solution compartment as possible in order to facilitate de-aeration of the test solution. By clamping the cell so that the cross-member is vertical, the molten... 

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