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HEN a quicklime is slaked directly to a wet putty, many of its properties are quite different from those of a putty made from the same lime by soaking the dry hydrate. The properties of a putty made from a dry hydrate sometimes change as the time of soaking the hydrate increases. Other differences in the methods of preparation of a lime putty produce differences in the properties of the putty. The causes of these differences have never been satisfactorily explained. Any national theory must account for several known facts. Many theories have been put forth, but only the colloidal theory will be discussed here. Theory for Difference in Lime PuttiesAccording to this theory, lime forms an irreversible colloid, or at least some irreversible colloidal material, during its slaking. If, in the slaking process, only sufficient water is used to produce a dry hydrate, the colloids are destroyed during the drying out of the hydrate and, upon subsequent treatment with water, will not again assume the colloidal state. But if sufficient water is used to leave the slaked lime as a wet putty, the colloidal properties are retained. The col-This would form the colloids necessary for plasticity. These authors have also shown that the magnesia of the quicklimes giving the non-plastic hydrates either completely hydrates during the hydration or else does not hydrate during the soaking. In this case no colloids would be present in the putty to make it plastic. Emleys states that plastic limes can be mixed with more water before they become sloppy or semi-liquid than the non-plastic hydrates. This is another indication of the presence of the colloids in plastic putties, and of their absence in non-plastic ones. The colloidal jelly-like structure of the plastic putty would require more water to Droduce fluidity Many of the properties of hydrated lime can be explained by the assumption that it is a non-reversible colloid. It is thought that the differences between a putty made directly from a quicklime and one made by soaking a dry hydrate may be due to the difference between their colloidal content. In this article it is shown that most putties contain positively charged particles and therefore exhibit cataphoresis to a limited extent. The amount of this cataphoresis is greatest for plastic putties and least for non-plastic putties. The theory is developed that plastic limes owe their plastic properties to their power of forming charged particles upon soaking or slaking. By an adaptation of the theory of Donnan's membrane equilibrium it is shown that the charged particles hold around them a film of solution, which so lubricates the particles as to make the putty plastic.loidal material present modifies the properties of the lime putty and causes the differences observed between the putties made directly from the quicklime and those made by soaking the dry hydrate. It is thought that plasticity, as well as some other properties of lime, depends upon the presence or absence of colloids.This theory explains several of the known facts concer...

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Fluorine was first prepared in quantity by H. Moissan2 by the electrolysis of anhydrous hydrofluoric acid rendered conducting by the addition of potassium hydrogen fluoride. Moissan began with a platinum U-tube as his electrolyzing vessel, the openings in which were closed with fluorite stoppers in which the electrodes of platinum-iridium were set. Later he found that copper would serve equally well as an electrolyzing vessel but that platinum electrodes must be used, Fig, I. With copper electrodes, polarization took place due

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While pure aluminum could not be deposited from a solution of aluminum chloride in formamide, alloys of aluminum with iron, and with zinc could be deposited. The quantity of aluminum reached 17.65 per cent in the alloy with iron. The addition of dry hydrochloric acid gas to the baths improved the deposits from solutions in formamide of the chlorides of most of the common metals, but interfered with the decomposition of aluminum alloys.INTRODUCTION.

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Fluorine has been obtained by the electrolysis of caesium acid fluoride using a Mathers cell constructed of magnesium. The caesium acid fluoride has a lower melting point and can be more easily regenerated than the usual potassium acid fluoride electrolyte.INTRODUCTION.