Indifferent point

The two branches of the solubility curve of a hydrate join each other at the indifferent point where the saturated solution has the same composition as the hydrate.— Let us take a... 

In 1884 Guthrie described the indifferent point of etbylamine hydrate, indifferent point which corresponds to the temperature —8° in 1885 Roozboom studied the indifferent points of hydrochloric and hydrobromic hydrates in 1889, in a work of capital... 

Pickering likewise undertook the study of the combinations which the amines form with water, a subject which had already furnished Guthrie examples of indifferent points Pickering found in his turn the existence of these points. 

In a very important investigation on the hydrates of ferric chloride, Robzboom showed the existence of an indifferent point for each of the four hydrates which ferric chloride may form. These indifferent points correspond to the following temperatures ... 

Van t Hoff and Meyerhoffer recognized the existence of the two branches of the solubility curve and of the indifferent point for the hydrate MgG 12H20 this indifferent point corresponds to the temperature —16 .3 C. 

The solution of lithium carbonate in melted potassium carbonate gives a solid double salt whose formula is KLiCXlj the temr perature of the indifferent point is 616 C. The melted mixture of sodium borate and sodium pyrophosphate gives a double salt formed by the union of one molecule of each of the simple salts the temperature of the indifferent point is about 960 C. Besides these examples furnished by melted salts, we may... 

Indifferent point of a double mixture —solution p-porting the pressure it and brought to the temperature T is in indifferent equilibrium in contact with a hydrat salt if, at this temperature and under this pressure, the saturated solution has the same composition as the hydrate when a double mixture is in equilibrium at the pressure it and temperature T the composition of each of the two phases into which it is divided is determined if these two phases have the same composition, this state of equilibrium is indifferent. 

Second Case Between the points and (Fig. 65) the curve D has a point I, OF ORDNATE P SMALLER THAN ALL THE others.—According to the second theorem of Gibbs and of Konovalow, this point is an indifferent point when the liquid and the saturated... 

CURVE D HAS A POINT I, OF ORDINATE S GREATER THAN ALL THE OTHERS.—The curve d also passes through this point I, which is an indifferent point (X=a =f), and has there an ordinate greater than all the others. Outside of the points I, the curve d is constantly bdow the curve D,... 

The first and last of these solids excepted, each of these substances corresponds to a solubility curve consisting of two branches meeting in an indifferent point in the preceding chapter (p. 225 ) we have indicated the temperatures to which these four indifferent points correspond. 

Except the fusion curve of ice, which rises from right to left, each of the solubility curves is formed of two branches meeting in an indifferent point one observes, therefore, in all, five indifferent points C, E, G, 7, L. The upper branch of the solubility curve of each hydrate meets the lower branch of the solubility curve of the hydrate which immediately precedes it in the above... 

The indifferent point J of the trichloride IG, the coordinates of this point are... 

The phenomenon becomes complicated when the two melted mixed salts may form a double salt to the two curves C, and Cj it is necessary in this case to join the solubility curve X> (Fig. 79) of the double salt in the liquid mixture this curve possesses in general an indifferent point I its points of intersection a>i, with the curve C, are eutectic points. 

This does not mean to say that the two curves C and c may not have, in certain cases, a common point I at the temperature d, which serves as abscissa to the point /, the mixed crystals may remain in equilibrium in contact with a liquid mixture of the same composition, so that this equilibrium state is indifferent. At the indifferent point I the two curves have a common tangent parallel to OX this point is therefore, for the two curves, a point of maximum ordinate or of minimum ordinate. 

The curve C, formed necessarily by two branches both S3mi-metrical with respect to the line X, has, for the abscissa a point of maximum ordinate. From the first theorem of Gibbs and Konovalow (Art. I94 which may be applied to the double mixture formed by the mixed crystals and the mixed liquid, this point belongs also o the line c, for which it is also a point of maximum or minimum ordinate. At this indifferent point I the mixed hquid, which is inactive by compensation, must give, on freezing, mixed holoedral crystals of composition x=i. 

From what we have just said, the freezing-point curve of this definite compound does not possess an indifferent point the point... 

In other cases, the freezing-point curve of the definite compound has an indifferent point the three freezing-point curves have then, very exactly, the arrangement shown in Fig. 79, p. 2 1. Such would be the case realized, according to Le Chatelier/ by the alloys of copper and antimony within which the definite compound SbCug may be formed. 

Double liquid mixtures. The temperature at which the two layers have the same composition does not corre nd to an indifferent point.—With W. Alexejew and V. Rothmund, let us take a mixture of water and phenol the mixture of these two liquids is not always homogeneous when the proportions of water and phenol are properly chosen, it separates into two layers of different composition and densities, thus forming a double liquid mixture which is a bivariant system. 

One might think this phenomenon comparable to those studied in Chapter XI, and that the point F is an indifferent point ohere two distinct liquid layered but of the eame composition, are in equilibrium with each other. 

The critical point for the vaporization of a single fiuid, page 812.—236. Double liquid mixtures. The temperature at which the two layers have the same composition does not correspond to an indifferent point, 814.—237. This temperature is a critical temperature, 816.—238. Mixtures which separate into two layers at temperatures lower than the critical temperature, 817.—239. Mixtures which separate into two layers at temperatures above the critical point, 818.—240. Infiuence of pressure on the critical temperature of a double liquid mixture, 819.—241. Vaporization of a mixture of two liquids critical line dew surface surface of ebullition, 819.—... 

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