The effects of nickel flashing on thermal-shock resistance of ceramic coating and mill additions of cobalt oxide on enamelling in nitrogen stream were studied from the points of interfacial microstructure proposed and adherence strength.
The new method for measuring thermal-shock resistance of ceramic coating is that the coated specimens are heated for 5 min. at the specified constant temperature which is taken either as the maximum saftey-temperature for actual use, or (0.7-0.8)×(enamelling temperature 3°C), and rapidly cooled in water. These heating and cooling operations are repeated until the gain in weight by oxydation of base metal becomes comparable with loss by peeling off. Then the relation between the amounts of peeling of coated layer and times of repeating will be expressed by a curve which has asymptotic constant value of saturation. From this curve thermal-shock resistance, R(%), can be calculated by following formula.
R(%)=Maxium amounts of peeling/Initial weights of coating layer×100%
The resistance, is thought to be nearly proportional to the adherence strength at room temperature. However, the existence of ferrosilicate layers which develope at 850°C for 30 sec. on interface by prefiring of nickel flashed base metal. Also increases thermal-shock resistance. From this reason, it is considered the ferro-silicate layer whose thickness is about 2-3μ, acts as to decrease the maximum amount of stress occured in coating layer.
The catalytic action of metallic nickel deposited by nickel flashing, being expressed by Fe₃O₄+Fe+Ni→4FeO+Ni, is promoted by acid etching after nickel flashing. Therefore, the kinds of acid and etching methods are important procedures for good enamelling.
For firing in nitrogen stream, mill additions of cobalt oxide are effective to increase adherence strength and thermal-shock resistance. Most effective addition is 3% CoO. This is due to the fact that selective galvanic corrosion of CoO remarkably occurs at this content and this corrosion state can be seen by the micro-photographs of interface. (Fig. 12)
When the galvanic corrosion of CoO and reducing action of nickel flashing simultaneously act during enamelling, these actions cancel each other so that both of thermal-shock resistance and adherence strength of specimen greatly decrease, in general.

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The author examined capillary water absorption under the pressure of nearly 3mm H₂O of Portland cement mortar specimens, 40×92φmm, added with 20 kinds of inorganic chlorides and sulphates and comparedd the results with non-added mortars.
The chlorides used are Mg-, Sn⁺⁺-, Na-, K-, Cu-, Mn⁺⁺-, Ba-, Fe⁺⁺-, Fe⁺⁺⁺- and Al- and the sulphates used are Na-, K-, Cu-, Zn-, Al-, Mn⁺⁺-, Fe⁺⁺-, iron alum, chrome alum and common alum.
The mixture of 1 part cement and 3 parts Japanese standard sand was kneaded with acqueons solutions of these salts, the solution-cement ratio being 0.80. Added quantities of the salts are equivalent, as anhydrides, to 1 and 2% of cement. The water-cement ratio of non-added mortar is also 0.80. Chloride-added specimens are cured in 20°C moist air and sulphate-added ones in 20°C water until one day before the day when absorption test is to be made. The test was made at ages of 7 and 28 days after mixing by the use of apparatus that had been designed by the auther and described in his foregoing paper. (J. Ceram. Assoc., Japan 63, 55-61, 1955 or Zement-Kalk-Gips 8, 113-118, 1955). Besides absorption test, strength-test was made at ages of 7, 28 days and 3 months. The results of absorption test are shown in Tables 2, 3 and 6. Among 20 kinds of the salts used, KCl and NaCl have the largest effect of diminishing capillary absorption. The additions of NaCl and KCl increase bending strength of the mortar at ages up to 3 months, but decrease compressive strength at 28 day and 3 month ages. The absorption-evaporation ratio of the non-added and nearly water-saturated cement mortar is nearly 1, but that of mortars having additions, which are effective for diminishing capillary water absorption is less than 1.

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Origin of pores developed in potash feldspathic glasses which compose a important part of porcelain body, is confired, and development of them during firing is studied. Pore distributions in soda feldspathic glasses are also compared with those in potash ones. Results obtained are summarized as follows:
(1) The greater the ignition loss of feldspars is, the more the number of pores in their glasses increases (Figs. 1, 4).
(2) Pre-heating of the same specimen at 1000°C for 2hrs. does not cause any change of pore distributions in the glasses (Figs. 3, 4)
(3) The quantity of pores present in the glasses does not depend upon the amount of air included between feldspar grains of the specimens (Figs. 6, 7).
(4) Addition of kaolinite to feldspar does not increase the pore development in the glasses, but rather decreases it, when too much added (Figs. 8, 9).
(5) From the results mentioned above, origin of pores in potash feldspar glass is to be concluded as follows: A part of gas released by heating from impurities, such as clay minerals, included in the feldspar grains, may be retained within the specimens until the melting of the feldspar grains. The gas may be remained even in the melt, and then developed into pores.
(6) With rising temperatures pores expand evenly and separately (Figs. 10, 11).
(7) With soaking time, on the contrary, pores are jointed each other with equal chance, consequently their number gradually decreases, and therefore their size markedly increases (Figs. 12, 13).
(8) Pores are neither drifted upwards nor expeled out of the potash feldspar melts, even of 1370°C, or soaked for 7hrs. at 1300°C (Figs. 14/19).
(9) Soda feldspar glasses is more (nearly 50-100%) abundant in pores than potash feldspar ones, while the size of the former is apparently smaller than that of the latter. Such differences may explain partially the inferiority of transluency of soda feldspar glass compared with that of potash feldspar one.

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The humus content of raw samples of koalin, Kibushi-clay, Gaerome-clay, pyrophyllite, sericite, pottery stone and stoneware clay was determined by Tulin-Seki method.
Selected raw samples of Kibushi-clay and Gaerome-clay were treated with H₂O₂ and washed dist. water, then their dispersion, sedimentation volume, viscosity, plasticity, swelling and decomposition of Fe₂O₃ by introducing SO₂ in slip were compared with dist. water-washed raw clays.
Effects of humus upon loss, on ignition, thermal expansion and firing shrinkage were also studied.
The conclusions are as follows: (1) clays contain humus not a little, but no relati ons exist between its content and their color or name which suggests their existence; some Kibushi-clays have little humus; (2) no relations, are found between humus content and pH value or swelling of clays; (3) the decomposition degree of H₂O₂ to humus is independent by its concentration; (4) some humus is decomposed by H₂O₂ so readily, but another is not so; (5) H₂O₂-treatment of clay not only decomposes humus-clay-complex but also eliminates soluble salt, so that treated clay has much dispersion degree and increase in viscosity; (6) H₂O₂-treated clay has low sedimentation rate and high sedimentation volume; (7) humus in clay is decomposed at about 250°-550°C; (8) the decomposition of iron compounds in clay by introducing SO₂ gas in clay slip is accelerated by the addition of H₂O₂ in slip; (9) the amount of thermal expansion of humus bearing clay at the decomposion temperature of clay is less than that of H₂O₂-treated clay; but has much contraction at about 100°-200°C owing to absorbed moisture.

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