Jena glass; and its scientific and industrial applications

9781236376435: Jena glass; and its scientific and industrial applications

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902 Excerpt: ...L= 4-81 therms per second. S =-02318 w=-29329 o-=-13944 Hence I is found by (1); and by the help of formulae for the transmission of heat across a layer of air, the value 20-156 was obtained for the relative conductivity k at the temperature Hi + s)= 36-02. This is to be multiplied by the absolute conductivity of air at the temperature of the air layer, which is about-00006, giving-00121 as the absolute conductivity at 36. The value finally adopted for the absolute conductivity K of the glass in question (the lead silicate glass 69) at 25 C. was 001083. Experiments conducted in the same way gave for glass 79 (a silicate containing soda and zinc oxide) at the same temperature, K=-001931. 92. Several comparative observations were made by inserting one of two glasses between the first and second copper plates, and the other between the second and third; the formula employed being L = l+w,: (3) which reduces to j (i k)- (k k) + 000154 DR (,-tjTM; (4) KY and d1 being the conductivity and thickness of the upper glass plate; K, d of the lower; D the thickness of the middle copper plate; R the common radius of the plates. For results, see the next article. 93. Relation to Chemical Composition. Paalhorn's values for the absolute conductivities (in c.G.s. units) of the glasses which he tested (namely the 15 glasses 69-83 in Winkelmann's list, Art. 67), are given in the following table, under the heading "observed." They are for temperatures not differing much from 25 C. Paalhorn adopted, on the basis of these results, a set of coefficients for expressing the absolute conductivity of a glass as a linear function of the percentages of its constituent oxides; and Winkelmann subsequently suggested changes in the coefficients for B203, ZnO, MgO, BaO,...

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