Experiment were carried out to find the amounts of alumina and ferric oxide dissolved from “Jomon-doki”, a Japanese prehistoric unglazed earthenware, by hydrochloric acid. The earthenware was a middle age “Jomon-doki” and was found by C. Kawashima in the ground of the Tokio University Of Engineering. Fine powder of 13 pieces of the eathenware and that of 6 pieces among them reheated at tempratures varying from 500° to 1000°C every 100°C for 1 hour were used as the samples of the experiments which were digested in 10% hydrochloric acid at 85°C for 40 minutes.
The solubility of Al₂O₃ and Fe₂O₃ contained in the samples ranged between 19 and 83% and between 39 and 99% respectively.
The solubility of Al₂O₃ and Fe₂O₃ contained in the reheated samples declined suddenly at the reheating temperature of 800°C, the proportions of dissolved Al₂O₃ and Fe₂O₃ to their contents in the samples heated at 1000°C being only 1-3% and 8-15% respectively. The relation between the temperature of reheating and the amount of dissolved alumina was similar to the case of ka olin. That Fe₂O₃ behaved like Al₂O₃ is somewhat interesting.
These results suggest that the firing temperature of the earthenware was probably about 700° to 800°C or lower. On the Other hand, when the absorption and porosity reported previously are compared to those of Japanese brick clays as formerly reported by S. Kondo, the firing temperature seems to be about 900°C. However, since the pores of the earthenware should have been partially closed by the products of rehydration and other minute substances, it is more probable that the temperature was about 700° to 800°C
The curves showing the relation between the temperature of reheating and the solubility of alumina indicate that the earthenware had undergone rehydration while it had been buried in earth for several thousand years.

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To melt glass in the course of glass manufacturing a tank furnace or a pot furnace is usually employed. In the former a glass batch is continuously heated in melted state for a considerably long period until it is worked after being charged in the furnace. while in the latter thebatch is being melted for 1-2 days after being charged likewise. In either case it is usual that a certain amount of cullet is to be added to the batch, in the factory.
The present study has been aimed at the observation on the variation of oxidation with the iron oxides contained in the glasses in cases where a given glass is continuously melted for a loger period and where the same given glass is repeatingly melted.
(A) To a soda-lime-silica glass batch has been mixed ferric oxide having amount corresponding to 1% for the glass. The mixture has then been melted for duration of 10 days in a pot and every day a test piece has been taken out therefrom and tested the amounts of FeO and total iron as Fe₂O₃.
The following table shows the amounts of FeO and total iron as Fe₂O₃ in the test pieces, and the percentage of FeO/FeO+Fe₂O₃ calculated from the said amounts.
(B) A same soda-lime-silica glass batch mixed with an equal amount of ferric oxide has been taken. The batch has been melted and a small quantity for test has been taken therefrom, and the rest has then removed from the pot, throwing it into water to make it a water cullet. After drying the said cullet it has again been melted by placing it into the pot used before. The process has been repeated seven times. The amount of FeO in the glass and the amount of total iron as Fe₂O₃ and the percentage of FeO/FeO+Fe₂O₃ have been calculated the said amount, which is given below:
From the above experiments it has been arrived that in case a glass in continuously melted for a longer period and in case the same glass is repeatingly melted for several times the amounts of FeO contained in the glass decrease gradually, while amounts of total iron oxide increase through they be just slight. Consequently it will be apparent that the percentage of FeO/FeO+Fe₂O₃ is tending to decrease gradually. By the way, it has been seen that the increase in the amounts of total iron oxide is due to the pot corrosion, and it is worthy to note that the said pot corrosion is heavier in case of repeated melting than in the case of continuous melting.

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The authors report, in continuing their previous studies I-XIII on mixed Portland cements, the further results of comparative studies on expansion or contraction and corrosion of hardened mortars of various cements by curing in various salt solutions. The main points of the present communication are abstracted from the original Japanese paper.
(1) Two sorts of Portland cement clinker and 6 sorts of various admixture (2 sorts of spent shale, one of basic blast furnace slag, 3 sorts of natural siliceous earth containing large amount of soluble silica) are mixed in proportions 60:40 or 50:50, and ground to various cement samples (2 sorts of common Portland cement and 12 sorts of mixed Portland cements).
(2) The specific gravity, fineness, setting time and chemical analysis of these cement samples are compared in the following table 1.
It is seen from these results, that the mixed Portland cements 90, 91, 92, 102, 103, 104, 105, etc., obtained from clinker and various natural siliceous earths containing large amount of soluble silica in proportion of 60:40 or 50:50, contain very large amount of total silica 45-50% or over 50% and are to be called as silica cement.
(3) Nextly, these cement samples are compared on their mortar strengths by the following two methods, (a) Compressive strength of 7.07cm cubical test piece and tensile strength of 8-type test piece were tested by dry or nonplastic mortar of small water cement ratio (w/c×100=26-32%), which is the method specified in the Japanese Engineering Standard for Portland cement (JES 28) and that for blast furnace slag cement (JES 29), and (b) Bending and compressive strengths by 4×4×16 (or 4×4×20) cm prismatic test piece from wet or plastic mortar of large water cement ratio (60-70%), which is the newly proposed method by Prof. M. Rôs in Switzerland and Dr. G. Haegermann in Germany, and the present author (S. Nagai) took the lead in using the modified method to study various mixed Portland cements.
(4) This prismatic test pieces of plastic mortar were applied to compare the expansion or contraction in water curing for various ages. The results of the measurement of expansion or contraction measured by planimeter are compared in the following table 2.
From these results, it is seen that mixed Portland cements are of quite equally superior quality in expansion or contraction to common Portland cement.
(5) Moreover, these prismatic test pieces are equally conveniently used for the comparison of mixed and common Portland cements to study the expansion or disintegration and contraction of hardened mortar cured vertically half dipped in variour salt splutions for long ages, by measuring with planimeter the distances between two cross marks on platinum, pins bedded on the test pieces. And then the bending and compressive strengths were tested and compared the decrease or increase to that cured in water for same ages. The results are shown in the following table 3, which are the suitable measure to discuss the resistibility of mixed Portland cement to various solutions of aggressive salts of the components of sea water.
From these results, some special points of mixed Portland cements are clearly seen, (1) Reaction of sulphate solution is considerably severe to common Portland cement, especially 10% Na₂SO₄ solution is more reactive that 10% MgSO₄ solution, (2) Mixed Portland cements are more resistive to sulphate and chloride solutions than common Portland cement, (3) Among chloride solutions, 10% MgCl₂ solution is more reactive than 10% NaCl solution, (4) Bending and compressive strengths of Mixed Portland cement mortars cured in 10% NaCl and 10% Na₂SO₄ solutions are larger that those cured in water, (5) Strengths of Mixed Portland cements cured in water for 56 weeks are nearly equal or a little stronger than those of common Portland cement cured in the same

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