T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y .
820
glass manufacture and glass literature to the high plane occupied by other exact sciences. If the worthy gentlemen whose publications have been criticized and others, whom the limits of this article have not included, will cooperate by publishing only formulas which are known t o be reliable, and will give proper directions for their use. they will materially assist in raising the plane of this important branch of science. UNIVERSITY OF PITTSBURGH, PITTSBURGH.
ON THE DENSITY OF SOME BORATE AND SILICATE GLASSES. By
EDWINWARDTILLOTSON,JR.
Nov., 1912
by fusing boric acid with the corresponding carbonates, it was difficult to drive off the last traces of carbon dioxide. This phenomenon was not observed in the preparation of the barium borates in this laboratory, although i t was difficult t o obtain borates containing high percentages of B,O,, free from minute bubbles, on account of the high viscosity of the melt. This doubtless explains some of the lower values for the observed density. The density of sodium oxides in silicate glasses is apparently somewhat greater than that assigned t o i t by Winkelmann. I n the following glasses the density was calculated, using 2.8 for sodium oxide:
Received July 1, 1912.
I n a former paper1 from this laboratory, attention was called to a method for calculating the approximate density of silicate glasses, and new density factors were proposed for several of the glass-forming oxides. I n calculating the density of some borate glasses prepared in this laboratory, it became evident that the density of boric trioxide in the glass is somewhat greater than the figure (1.9) given b y Winkelmann and Schott.2 Comparison with other published data, giving weight to the more careful measurements of density, showed 2 . 2 4 as the most probable value for the density of boron trioxide in these glasses. Table I shows the composition, the observed and calculated densities of several borate glasses from various sources. Table I1 shows the values for the density TABLEI. Density.
Percentages. Observed.
%Os. Ca(B02)~ Mg(B02)Z Zn(B0z)p Sr(BOd2 W 11
55.5 63.6 46.2 40.3 41.0
W 16
42.8
B a O 2 B ~ 0 8 46.37 Ba04B208 6 3 . 4 0 Na&i,Or 69.3
{
CaO 4 4 . 5 MgO 3 6 . 4 ZnO 5 3 . 8 SrO 59.7 ZnO 5 9 . 0 Ala, 5 . 2 PbO 5 2 . 0 PbO 53.63 PbO 36.60 NalO 3 0 . 7
2.7711 2.5201 3.320’ 3.254’ 3.5272
Calculated.‘ 2 .SO 2.40 2.99
....
3.17
Calculated.6 2.807 2.667 3.358 3.258 3.532
3.6912
3.42
3.785
3.5223 2.9223 2.3704
3.12 2.595 2.01
3.526 2.982 2.387
Tamman-Krysfallisieren und Schmelzen, p. 50. Winkelmann and Schott, loc. cit. a Tillotson. 4 Day and Allen, “Isomorphism and Thermal Properties of t h e Feldspars.” 5 Using Winkelmann’s factors. 6 Using modified factors. TABLE 11. Winkelmann Modified factors. factors. SO2. .2.3 2.3 Ba08. 1.9 2.24 NazO.. 2.6 2.8 CaO ............. 3 . 3 4.1 MgO 3.8 4.0 AlzO3.. 4.1 2.75 1 2
............
............
.......... ............. ..........
employed by Winkelmann and Schott and those now proposed for giving a more accurate calculated value of the density of the glass. Inspection of the figures in Table I shows that in the case of the carefully prepared borates the observed and calculated densities are in good agreement. Tamman3 observed t h a t in the preparation of these borates THIS JOURNAL, 3, 897 (1911). 2 Ann. d. Phys. und. Chem., 49,401 (1893); 61, 697 (1894); “JenaGlass a n d I t s Industrial Application,” Hovestadt (English Edition), p. 148. 8 Krystallisierelt und Schmelzen. 1
-
Percentages. No. W 25 W 8
SiO2. 71.0 68.3
ZnO ZnO
12 Na2O 1 7 . 0 5 . 0 NazO 1 0 . 8 A1203 1 . 0 PbO 8.1
Obs. 2.572 2.629
Density. Calc. 2.566 2.639
This is further illustrated b y the soda barium silicates shown in Table 111. TABLE 111. SiOz. Per cent. 74.50 66.15 61.70 53 .OO 71.70 67.60 64.55 61.30 58.30 55.34 52.46 49.95 46.91 44.25 79 .oo 75.85 67.45 62.60 57.20 51.14 36.84 1 Using 2 Using
BaO. Per cent.
...
NazO. Per cent. 25 .SO 20.85 18.50 13.40 22.65 19.85 17 .OO 19.50 12 .oo 9.56 6.94 4.55 2.29
Density. Found.
2.437 13.00 2.64 19.10 2.752 33.60 3.06 5.65 2.491 2.633 12.55 2.759 18.45 2.824 24.20 2.934 29.70 3.072 35.10 3.212 40.60 3.367 46.00 3.476 50.80 ... 3 . 6 5 55.75 15.85 5.15 2.46 14.80 9.35 2.514 12.20 20.35 2.722 10.80 2.845 26.60 9.20 3 06 33 60 41.50 7.36 3.224 3.95 60.40 2.76 Winkelmann’s factors. modified factors.
Calc.’
Calc.2
2.37 2.59 2.725 3.03 2.45 2.57 2.69 2.80 2.925 3.05 3.195 3.35 3.50 3.67 2.43 2.50 2.72 2.84 3.01 3.265 3.88
2.41 2.625 2.755 3.055 2.50 2.615 2.72 2.83 2.96 3.08 3.22 3.37 3.51 3.69 2.455 2.523 2.73 2.87 3 04 3.245 3.90
Error.1 Error.2 Per Per cent. cent. f2.O +10 +2.0 +0.6 +2.0 -0.2 +1.0 +0.1 +1.4 -0.2 + 2-~ .4 c 0.. .7 +2.5 +1.4 +0.8 -0.2 +0.3 -0.9 f0.7 -0.2 -0.2 +0.5 -0.1 +0.5 -1.1 -0.8 -0.5 -0.5 +0.2 +1.2 -4.4 +0.6 -0.3 +0.1 +0.2 -0.9 +1.6 +0.7 -1.3 -0.9 +1.8 +1.2
It will be seen that the observed and calculated values for the density of these silicates are in very good agreement and as the compositions of the glasses vary over wide limits, it is evident that the method is capable of giving excellent results with a large variety of glasses. SUMMARY
I. The densities of some pure borate glasses have been examined and a n empirical factor determined for the density of B20, in the glass. The factor adopted is 2 . 2 4 instead of 1.9as given by Winkelmann. 2 . The densities of some soda barium glasses have been studied and the factor 2.8 for the density of Na,O has been adopted in place of 2.6 employed b y Winkelmann. DEPARTMENT O F INDUSTRIAL RESEARCH, UNIVERSITYOR KANSAS, LAWRENCE.
I
