One of the present authors (S. Nagai) had already proposed (Gypsum & Lime No. 29, 6-10 1957), that it is the most important for building to make and use some cheap cement as masonry cement for using as cement mortar to cementing natural stone, common brick, concrete block, etc., and also for mortaring on concrete wall, ceiling, etc. of all biuldings. In that paper, a special kind of masonry cement was prepared from residues from slaking quick lime to slaked lime and calcined dolomite to dolomit plaster or slaked magnesia-lime fertilizer.
In the present report, the further studies of other kind of masonry cement were reported as following; (1) the preparation of another special masonry cement was prepared from water granulated slag from iron blast furnace, slaked lime and some kinds of cement admixtures, e.g., natural siliceous matter, shale or slate powder, fly ash from pulverized coal, siliceous residue from steam pressure refinery of sulphur, etc., (2) these several kinds of masonry cements were tested their setting time, chemical compositions, and hardening property by 1 : 2 cement-sand plastic mortar.
In these special masonry or mortaring cements, the most important and special point is to knead with dilute, e. g., 2, 3, 5% NaOH solution, and to have very superior hardening strengths of both bending and compressive testings. These hardened strengths were observed to be not smaller than those of common Portland cement. This is the most remarkable point of this special lime-slag (and admixture) cement.

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The content of carbon dioxide in quick lime or slaked lime is very valuable data not only for the controlling of process but for the classification of quality. According to Japanese Industrial Standards R 9001 (1954), carbon dioxide in lime is determined by Geissler's method or Schroedter's method. However these gravimetric methods are very difficult in operation and more neither enough in accuracy, precison nor rapidity.
The present authors studied on the application of volumetric method instead of gravimetric method to the determination of carbon dioxide in lime and confirmed the high reliability, rapidity and the large applicable field of this method extending to dolomite and gypsum not only lime.
The apparatus is connecting of one for removing carbon dioxide gas contained in the leading air, one for decomposing sample and one for measuring carbon dioxide gas in series (See Fig. 1). The procedure is as following, firstly lead the gas happened by decomposing sample to burette, measure the amount of the gas and next remove carbon dioxide by passing the gas into the solution of potassium hydroxide. Finally calculate the weight percentage of carbon dioxide from the amount of the gas reduced by absorption.
The determined results of carbon dioxide in natural calcite, quick lime and slaked lime were analysed by statistical analysis. Those data often become unstable if the form and capacity of the bottle for decomposing sample or the velocity of gas for leading to burette change. For selecting the oputimum condition, the small streamlined bottle having capacity 50 cc was produced by way of experiment and the leading velocity of gas was regulated from 10 to 20cc/sec. In comparison with gravimetric methods, the repeatability of this method is higher, the significant difference is found between the mean of Geissler's method and of this method, besides Schroedter's method may be useful for simplified method if the required precision is not so severe because the dispersion of the data is large but constant. The precision of this method is very high as showing the standard deviation from 0.05 to 0.12 at the range from 1.5 to 2.0 per cent of carbon dioxide. The time required for determination is probable to be reduced from 2/3 to 1/2 of the time by gravimetric method. The rapidity of this method will be higher if the calculation by nomograph is employed.
For an example applying this method to the controlling of quality, the analysis of variance on the sampling error among 5 random samples and the analytical error among 3 analysts was held. One bundle contained 20 kg of slaked lime is selected for one lot of experiment and the ununiformity of carbon dioxide in the lot was confirmed.

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Lime from limestone reacts with water to form Ca (OH) ₂ with considerable liberation of heat, but from shell reacts very slowly, without being pulverized, in a large quantity of water.
In vacum flask, lime from shell, when slaked with a suitable quanitity of water, gives off heat and is pulverized. If it is put in air, it is weathered gradually and pulverized.
Lime from oyster, which contains SO₃ and alkali, hardens itself with water. The statement above-mentioned can be proved by the fact that the mixture of Ca (OH) ₂ 95%, CaSO₄·2H₂O 5% and KOH 2%, when calcined at 1000°C, hardend itself with water.

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