The results of these are summarized as follows: It was understood to be difficult to hydrate the natural anhydrite (CaSO₄) and to get good crystals of hydrated gypsum (CaSO⋅2H₂O), than getting the gypsum from some byproduct anhydrite.
But, the good crystalized gypsum can be easily obtained by the recrystalization of the natural anhydrite with continuous stir in some solutions of NaCl, NaCl and K-alum, (NH₄)₂SO₄, NH₄NO₃ or NaNO₃. Especially, 15% solution of NH₄NO₃ was so effective that perfect hydrated granular gypsum was obtained by only 24, 36 horus reaction in this solution at room temperature.
The effects of concentration of solution, fineness of anhydrite, reaction temperatures and some effects of organic salts on these reactions were also discussed.
The plaster of paris made of the hydrated gypsum was found to have very good properties.

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Calcined gypsum is made by the radiation of infrared lamps. Temperature necessary for calcining gypsum crystals can easily be controlled during radiation. We have investigated on the relation between temperature, weight of sample, time of reaction, and number of infrared lamps. This method of calcining gypsum crystals by infrared lamps is very advantageons comparing with other ordinary method espesially in small scale experiments.

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The relations between hemi-hydrate and slags with latent hydraulic properties were discussed by Wünenberg in 1951, and those between the former and calcium hydro-oxide were in formed by K. Aichinger and B. Wander in 1950. Schöenhöfer also has discussed about the physical characteristics of the hydraulic property,
The authors, applying slag on calcium hydro-oxide and admixing some quantities of certain exciting chemicals, recongnized a prominent increase of tensile strenght. In other words, by the study of the authors, it was found that the application of only 1.5% wt. of slag can give a prominent extensions the physical properties of Gypsum.

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When we Synthesize CaSO₄⋅2H₂O and recover the brine by utilizing by-product CaCl₂ of Ammonia-Soda process and by-product Na₂SO₄⋅10H₂O of rayon industry, glanular and dense crystals of CaSO₄⋅2H₂O and the concentrated NaCl solution are obtained by means of addition of a little amount of certain organic substances—partecularly Na-citrate—to the reactive solution, resolving Na₂SO₄⋅10H₂O into NaCl solution, and holding the reactive solution slightly basic.

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