The phase rule and its applications . rature of transition of thetwo enantiotropic forms. At this point the two solubilitycurves must cut, for since the two forms are in equilibriumwith respect to their vapour, they must also be in equilibriumwith respect to their solutions. From the table on p. 63 itis seen that potassium nitrate, ammonium nitrate, silver nitrate,thallium nitrate, thallium picrate, are capable of existing in twoor more different enantio- 66tropic crystalline forms, therange of stability of these coforms being limited by defi-nite temperatures (transitiontemperature^. Since th
The phase rule and its applications . rature of transition of thetwo enantiotropic forms. At this point the two solubilitycurves must cut, for since the two forms are in equilibriumwith respect to their vapour, they must also be in equilibriumwith respect to their solutions. From the table on p. 63 itis seen that potassium nitrate, ammonium nitrate, silver nitrate,thallium nitrate, thallium picrate, are capable of existing in twoor more different enantio- 66tropic crystalline forms, therange of stability of these coforms being limited by defi-nite temperatures (transitiontemperature^. Since the tran-sition point is not altered by 50a solvent (provided the latteris not absorbed by the solidphase), we should find on 40studying the solubility ofthese substances in water that 1the solubility curve wouldexhibit a change in direction at the temperature of transition. As a matter of fact this has been verified, more especially in the ca* of ammonium nitrate l 1 W. Miiller and P. Kaufmann, ZeiUchr. physikal. Cliem. 1903, 42. Fig. 2: u6 THE PHASE RULE and thallium The following table contains the valuesof the solubility of ammonium nitrate obtained by Miiller andKaufmann, the solubility being expressed in gram-moleculesNH4N03 in ioo gram-molecules of water. In Fig. 27 theseresults are represented graphically. The equilibrium point wasapproached both from the side of unsaturation and of super-saturation, and the condition of equilibrium was controlled bydeterminations of the density of the solution. Solubility of Ammonium Nitrate. Temperature. Solubility. Temperature. Solubility. 12-2° 34-50 32-7° 57-90 20-2° 43-30 34-0° 58-89 25-050 48-19 35-o° 59-80 28-0° 51-86 36-0° 61-oo 30-00 54-40 37-5° 62-90 30-2° 54-6i 38-0° 63-60 3i-9° 57-20 39-o° 65-09 32-1° 57-6o 40-0° 66-80 From the graphic representation of the solubility given inFig. 27, there is seen to be a distinct change in the directionof the curve at a temperature of 32°; and this break in th
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