The present study relates to a case where metallic powder is used as a reducing agent in glass melting.
In case FeO and other reducing substances are coexisting in glass it is imposible to analyse amounts of respective substances through the present day processes of analysis. The author has therefore chosen for temporary convenience the following method in this study.
A glass containing a little amount of iron oxide has been melted by adding therete metallic powder as a reducing agent. The glass obtained has then been treated by a method similar to that ordinary employed in quantitative analysis with FeO. Next, by titrating the amount of the total reducing substance with the N/100KMnO₄ solution the required number of c.c. has been found. On the other hand a total iron oxide in the glass has been measured as Fe₂O₃ and this has then been converted into an amount formed to FeO. The number of cc of said N/100KMnO₄ solution correponding to the amount of said FeO thus obtained.
By deducing the number of c.c. of the said N/100KMnO₄ solution used for the latter case FeO from the number of cc of the like solution used for the total reducing substance, the difference has been obtained and the said difference being an amount of the standard solution consumed by the reducing substances beside FeO in the Glass.
This method is not applicable to cases entirely disregarding the amount of iron oxide contained in the glasses but the same is applied to such glasses in which a difference in the iron oxide contents is in a narrow extent and to find out the relative value.
(1) A glass having metallic zinc added as a reducing agent
(a) Glasses have been obtained by adding to FA-1 glass batch the metallic zinc powder in such amounts corresponding to 0, 1, 2, 4 and 8% in weight of the glass.
(b) Glasses have been obtained by adding to FA-4 glass batch the metallic zinc powder in such amounts corresponding to 0, 1, 2, 4, 6 and 8% in weight of the glass.
(2) A glass having metallic magnesium added as a reducing agent.
(a) Glasses have been obtained by adding to FA-1 glass batch the magneum powder in such amounts corresponding to 1, 2, 4% in weight of the glass.
(b) Glasses have been obtained by adding to FA-4 glass batch the metallic magnesium powder in such amounts corresponding to 0, 0.1, 0.5, 1.0, 2.0 and 4.0% in weight of the glass.
The transmission curves of glasses of FA-4-Zn series and FA-4-Mg series have been sought.
In glasses of FA-4-Zn and FA-4-Mg series they have turned to yellowish instead of becoming bluish in spite of the fact that the amount of FeO in the glass has been increasing as the amount of the metallic powder added as a reducing agent has been increased.
It has been found difficult to ascertain the cause there of.

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In the present communication, the present authors report the further results of studies, continuing the previous reports (This Journal, 1934, 42, 399; 1935, 43, 719; 1936, 44, 143), on the effects of alumina Al₂O₃, magnesia MgO and boric oxide B₂O₃ to the water resistibility of ordinary soda-lime glasses of window glass, plate glass, rolled glass, etc. The following is the brief abstract from the original Japanese paper.
(1) As a standard glass of ordinary soda-lime glass type, was prepared the glass sample signed SCN-O, containing silica SiO₂ 72%, lime CaO 13% and soda Na₂O 15% as constant as possible.
(2) This 13% of lime CaO was displaced by 3% alumina Al₂O₃ from potash feldspar or kaolin, 3% by 2% magnesia MgO from dolominte or 6 (3+3)% from both of them, and 72% silica SiO₂ was displaced boric oxide B₂O₃ from borax. These natural raw materials, i.e., silica sand, potash feldspar, kaolin and dolomite, have the following chemical compositions.
Table 1-Chemical Compositions of Natural Raw Materials
(3) Using these chemicals and natural raw materials, batch mixtures were made, melted in chamotte crucible in gas furnace, by displacing lime by alumina, magnesia or both of them and silica by boric oxide in the amount of 2, 3 or 6% as above described. 9 samples of test glasses were thus obtained and their chemical composition were analysed shown in the following table 2.
(4) Samples of one sheet glass and two mould glasses were obtained from the market and used for the comparison in the present study. Their chemical compositions were analysed and compared with those of test glasses.
(5) These 12 glass samples were compared on their chemical compositions and specific gravities in the following table 2.
It is sorry that the chemical compositions of 9 test glasses deviated a little from the standard, owing to the impurities in the natural raw materials, from the melting chamotte crucibles, etc. The sign W shows the samples obtained from the market, and window or sheet glass WII and mould glasses WI and WIII. Some of these 9 prepared and 3 market glass samples have quite equall chemical compositions and specific gravities.
Table 2-Chemical Compositions and Specific Gravities of Glasses
(6) These glass samples were ground and grains of dia. 0.49-0.75mm were obtained by sieving and remaining between 64 meshes/cm²-sieve and 144 meshes/cm²-sieve. These grains were washed with alcohol and dried, and then tested on their solubilities in boiling water of (1) the atmospheric pressure, (2) 5 atm. pressure of steam papour, and (3) 10 atm. steam pressure, in silver gauze suspended in silver beaker or crucible. The water solution was titrated by N/50-H₂SO₄ solution and the amount of dissolved alkali was calculated, the weight decrease of glass grains was weighed, and then the ratio of these amounts of dissolved alkali and weight decrease was compared, as quite equally adopted in the foregoing reports. Some results are tabulated in the following tables 3 and 4.
Table 3-Comparison of Water Solubilities of Various Glass Samples under Atmospheric Pressure tested by the Grain Method
The following points are seen from these results, that (1) displacement of CaO by 3% MgO is not effective to the water resistibility of glass, (2) displacement of CaO by 3% Al₂O₃ is remarkably effective, (3) displacement of SiO₂ by 2% B₂O₃ is not effectve, (4) MgO and B₂O₃ are to be effective to lower the viscosity of molten glass metal at the working temperature, (5) window or sheet glass and mould glasses on the market are a little inferior in water resistability, owing to the insufficient amount of Al₂O₃, etc.
Table 4-Comparison of Water

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Experiments were made to supply some deficiencies in the third article of the series entitled “Microscopic Observation of Their Hydration”. Also the hydration for such small water cement ratios as used generally in concrete practice was investigated by optical and X-ray methods. The results are as follows:-
(1) With water cement rations of 1 and over as were used in the experiments of the third article, the uniaxial optically positive crystals A, whose ω_D and ε_D are 1.498 and 1.507 respectively, are produced in the earliest period. They are unstable and therefore are transformed before long into the hexagonal uniaxial negative crystals B whose ω_D and ε_D are 1.524 and 1.506 respectively. Also the uniaxial negative crystals C, which are produced in the later periods and whose ω_D and ε_D are 1.535 and 1.511 respectively, are small in quantity. Thus, although the crystals A and C play röles in the process of the aluminate, they are not important as the crystals B. In other words, the chief product of the hydration of the aluminate with much water in the crystals B belonging to the hexagonal system.
(2) With water cement ratios smaller than 1, crystals quite different to those described above are produced as the ratios decrease. Namely, instead of hexagonal crystals B, minute grains or fibers of regular system with ND of 1.604 are produced.
(3) The X-ray investigation indicates that the lattice constant of the regular crystals is about 12.454 Å.
(4) These results are not coincident to those given by Klein & Phillips, Thorvaldson, Koyanagi, and Bogue & Lerch. However they agree well with their summarised results.
(5) According to the X-ray observation, the regular crystals do not suffer any structural change even on standing for 35 days.

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