In continuing the previous studies, it is the main point to studing, in the present paper, on the special hydrothermal method for making gypsum hemihydrate CaSO₄⋅1/2H₂O by directly crystallizing out from gypsum crystal in the solution of various electrolyte of organic and inorganic salts, as following: (1) Sodium salts of oxalic, acetic, citric and tartaricacids, and Rochelle salt or potassium and sodium tartarate, and gelatine, and (2) Sulphates as Na₂SO₄, K₂SO₄, ZnSO₄, MgSO₄, Al₂(SO₄)₃, Cr₂(SO₄)₃, Fe₂(SO₄)₃, K₂Al₂(SO₄)₄, (NH₄)₂Al₂(SO₄)₄, K₂Cr₂(SO₄)₄ and (NH₄)₂Fe₂(SO₄)₄, phosphate as NaH₂PO₄, and borate as Na₂B₄O₇. In the former case of organic acid salt, sodium salt of citric acid was proved to be the most suitable electrolyte in water solution of 0.1-0.01%, to obtain good crystallized tabuilar or prismatic crystal of gypsum hemihydrate. In the latter case of various inorganic salts, Al₂(SO₄)₃ was observed to be most effective in its 5% or more concentrated solution. to obtain the hemihydrate above described.

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The thermal efficiencies of the kilns for firing the smoked-tiles are generally lower than that of the kilns which are used for the other ceramic products. The main cause in these lower thermal efficiencies of these kilns is found largely in the process of smoking or blueing. For that reason the consideration about the mechanism of smoking must be given.
In this paper, the author has investigated the processes of smoking generally in use to-day by the use of the gas analysis in a test tube furnace. And the results obtained are as follows:
(1) The “smoking” is a vapor phase cracking at the heated surfaces of the stock at 850° to 1000°C. Which is a natural transition to the pyrogenetic decomposition of the liquid products of the destructive distillation of wood accompanied by the formation of large amounts of coke and gas.
(2) The liquid products of the destructive distillation of wood play the chief part in “smoking”, and the gaseous products play one of the useful diluents.

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Various attempts to check simply the thermal expansion of glass without laborious measuring by dilatometer have been reported in a series of papers. The method described here is the one which makes use of the cylindrical glass-to-glass seals and observes the deviation of fringes in the photo-elastic stress pattern corresponding to the difference of expansion between two glasses.
It does not concern whether the tested glass is sealed inside or outside of the standard glass, inasmuch as the fact that the glass which shows higher expansion, introduces compression in the other and simultaneously tension in its own as is usually the case. The displacement of the fringe pattern is so sensitive to the residual stress that the slight difference of expansion is frequently detected even when the commonly used optical lever type dilatometer is unable to differentiate the expansion curves.
The experimental fact that the soda-lime glass is more sensitive than the soft lead glass for the same order of the difference of expansion will probably be attributed to the considerable difference of activation energy necessary for the release of stresses by viscous flow during cooling.
Since the displacement of the fringe is linearly proportional to the stress, we can calculate the residual stresses easily, the values of which should always be kept within a certain limit.
The method presented herein has been used in our laboratory and found to be practical for routine checking of the thermal expansion of glass.

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The field of application of electrostatic spraying, which already proved a good result in American enameling shops, has been restricted only for articles of flat shape, such as a range top plate, and the authors, in an attempt to extend this field of application to the domestic wares of more complicated form, made some investigations for the purpose of obtaining some basic data. The general idea based on was that we could use the electrostatic field most efficiently and hence secure the most uniform coating if it could be possible to suspend still the enamel particles in air by compensating the gravity force with the upward current of air produced by the mechanical draught in a spray booth.
From the lower end of the spray booth, composed of a vertical cylinder of 180cm long and 50cm in diameter, slip was injected upwards, and the air current in the booth was regulated to be about 100cm per second, which is necessary for keeping the particle at rest at the middle, by exhausting with a fan equipped at the top of the booth. Four square steel pieces having 2cm brim and 10 square cm base were stringed successively along a vertical line at the center of the booth with copper wires of 5cm long. A cylindrical cage of very large mesh composed of thin copper wires and 130cm in length and 30cm diameter, was supported by insulators to serve as a negative electrode, whose nearest distance from samples was about 10cm so that a static voltage of 28 kilo-volt can be applied without sparking over.
The authors confirmed that the uniformity of thickness of the coating can be appreciably improved by the existence of electrostatic field, for example, the thickness of the coating at the vertical surfaces increased from 8-17% to 29-102% of the horizontal, only on which the particles may deposit by usual mechanical methods, Further it was confirmed that, by applying the field, the efficiency was increased as much as two times of the usual method.

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