The present authors report, in continuing the previous studies (This Journal, 1934, 42, 399; 1935, 43, 719; 1936, 44, 143, 307; 1937, 45, 299, 522) the results of further comparative studies on the relation between water solubility or resistibility, chemical compositions and heat treatments of various glasses of soda-lime-silica series. The main points are briefly abstracted from the original Japanese paper, as following:
(1) As the standard so la-lime-silica glass, containing Na₂O: 15%, CaO: 13% and SiO₂: 72% (nearly Na₂O⋅CaO⋅5SiO₂), was prepared and signed SCN-C. The amount of lime was changed by alumina in the degree of about 1, 2 and 3% and obtained three kinds of glasses SCN-AI₁, SCN-AI₂, and SSCN-AI₃. These four samples of prepared glasses were ground to proper grains (dia.: 0.49-0.75mm), put in the special heat treatments by the same way in the previous reports V and VI, and then tested on their water resistibilities under atmospheric pressure or 5 and 10 atms. of steam pressure in autoclave. The replacement of lime by alumina was seen to increase considerably the water resistibilities of glasses of soda-lime-silica series.
(2) Nexty, the amount of 3-6% of lime was replaced by magnesia and five kinds of these glasses and one kind of standard soda-lime-silica glass. The formers are signed as SCN-MI₁, SCN-MI₂, SCN-MI₂, SCN-MII and SCN-MIII and SCN-MT, and the latter is SCN-E. These six samples of glass were treated by heating, quick or slow cooling, etc., and were clearly seen these glasses to be a little more resistible than that of simple soda-limesilica type as SCN-E.
(3) By the same way, lime of standard soda-lime-silica glass was simultaneously displaced by 3-5% alumina and 1-3% magnesia, or totally 5.2-5.9% of alumina and magnesia, and three kinds, SON-AM₁, SON-AM₂ and SCN-AM₃, of glasses for the comparative testing of the relation between water solubility or resistibility, heat treatment and chemical compositions of glasses, in the quite same way as adopted in the foregoing sections. The good results were obtained by these simultaneous introductions of alumina and magnesia in proper proportion and reducing the amount of lime to 6.8-7.3%. This type of chemical compositions (SiO₂: 72%, Al₂O₃: 2-3%, MgO: 1-2%, CaO: 7-9%, Na₂O: 15-16%) became now in Japan to the standard compositions of window glasses, plate glasses, bottle glasses, etc.
(4) The resources of alumina in the above section were obtained from the natural feldspar or alkali-kaolin, the latter being obtained from kaolin and alkali carbonate or alkali hydroxide solution, and magnesia was odtaineb from dolomite or talc powder. The using of artificial alkalikaolin and talc is clearly seen to be a quite new point for the glass making.
(5) From these results, some points were discussed with regards to the percentages of alkali solubility (A.L), weight decreases (W.D), and the ratio between these values, i.e., A.L/W.D×100. These ratios were observed to be nearly 10-20% at the testings under the atmospheric pressure, and 30-35% at the testings under higher pressures and temperatures (5 atms. and nearly 153°C or 10 atms. and 181°C). These values A.L/W.D×100, especially at the high pressure testings, were quita equall to that of Na₂O/Na₂O.xSiO₂×100, which becomes to be 34% in the case of x:2. Na₂O. xSiO₂ is the amount dissolved in water and equal to the amount of weight decrease (W. D) in the above experiments, and Na₂O is the dissolved alkalis, which can be determined by the titration with dilute acid solution, as adopted in the above experiments by N/50H₂SO₄ solution and obtained alkali

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A magnesite produced at Byakkozan in South Manchuria was fired to 600, 1100, 1500, and 1800°C. Then X-ray diffraction patterns of the products were compared one another by powder method. On the other hand, the effect of various fluxes on the fire shrinkage of pure magnesia or on its dead-burning behavior was compared by continuously measuring the linear change of dry pressed columnar test pieces, 2cm. wide, 1.5cm. thick, and 5cm. high, when they were heated in an cryptol furnace up to 1800°C, and also by tracing the change of the rate of shrinking with the rise of temperature.
The results of the experiments may be abridged as follows:
(1) Thermal dissociation of the magnesite was started at about 400°C and was nearly completed at 620°. Diffraction patterns of the magnesite which were fired to the four temperatures mentioned above were perfectly same. In other words, magnesite seems to produce periclase as soon as it dissociates.
(2) The rate of shrinkage of the test piece made of c. p. magnesia rose suddenly at about 1290° and attained its maximum value at 1385°, arriving at a nearly constant value at 1670°.
(3) Each of SiO₂, Al₂O₃, Fe₂O₃, Cr₂O₃, and Mn₂O₃ accelerated the shrinkage of magnesia, though the effcct was not so intense as for natural magnesite. A secondary shrinkage occurred with Al₂O₃ and Cr₂O₃, namely the rate of shrinkage rose again at about 1470° with Al₂O₃, and at about 1450° with Cr₂O₃. The other fluxes showed similar but less distinct tendencies. The effect of FeS₂ and PbSO₄ was not so intense as expected.
(4) The test pieces with 2% NaCl began to shrink at about 600° and completed the first shrinkage at a temperature a little over 1000°. Thus NaCl seems to encourage the shrinkage at comparatively low temperatures.
(5) The effect of precipitated CaF₂ was most remarkable. On its addition, the rate of shrinkage increased suddenly at about 900°, reached its maximum value at 1140°, and was reduced to almost zero at 1540°, the temperature for the maximum rate of shrinkage having been lowered by about 150°C. The effect of BaF₂ was also marked though weaker than the former.

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Der Verfasser zeigt zunächst einige Schwierigkeiten oder einige Nachteilen, die bei dem Trockenverfahren unter dem Presse entstehen, und ferner versucht den Ursachen solcher Erseheinung infolge einfacher Experimente und auf Grund von den Mechanik Pulverförmiger Massen zu erklaren.

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[in Japanese]

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