determination of the transition point of sodium sulphate decahydrate
(p. 136). The following figures give the results obtained by Meyerhoffer in
the case of the transformation:--
CuK_{2}Cl_{4},2H_{2}O <--> CuKCl_{3} + KCl + 2H_{2}O
the temperature being noted from minute to minute: 95deg, 93deg, 91.8deg,
91.7deg, 92deg, 92.3deg, 92.4deg, 92.2deg, 92.2deg, 92deg, 90.5deg, 89deg,
and then a rapid fall in the temperature. From this we see that the
transition point is about 92.2deg. It is also evident that a slight
supercooling took place (91.7deg), owing to a delay in the transformation,
but that then the temperature rose to the transition point. This is
analogous to the supercooling of a liquid.
A similar halt in the temperature would be observed on passing from lower
to higher temperatures; but owing to a lag in the transformation, the same
temperature is not always obtained.
{337}
V. Optical Method.--The transition point can sometimes be determined by
noting the temperature at which some alteration in the appearance of the
substance occurs, such as a change of colour or of the crystalline form.
Thus mercuric iodide changes colour from red to yellow, and the blue
quadratic crystals of copper calcium acetate change, on passing the
transition point, into green rhombs of copper acetate and white needles of
calcium acetate (p. 260). Or again, changes in the double refraction of the
crystals may be also employed to ascertain the temperature of the
transition point. These changes are best observed by means of a microscope.
For the purpose of regulating the temperature of the substance a small
copper air-bath is employed.[404]
VI. Electrical Methods.--Electrical methods for the determination of the
transition point are of two kinds, based on measurements of conductivity or
of electromotive force. Both methods are restricted in their application,
but where applicable give very exact results.
The former method, which has been employed in several cases, need not be
described here. The second method, however, is of considerable interest and
importance, and calls for special reference.[405]
If two pieces, say, of zinc, connected together by a conducting wire, are
placed in a solution of a zinc salt, _e.g._ zinc sulphate, the potential of
the two electrodes will be the same, and no current will be produced in the
connecting wire. If, however, the zinc electrodes are immersed in two
solutions of _different_ concentration contained in separate vessels, but
placed in connection with one another by means of a bent tube filled with a
conducting solution, the potentials at the electrodes will no longer be the
same, and a current will now flow through the connecting wire. The
direction of this current _in the cell_ will be from the weaker to the more
concentrated solution.
The greater the difference in the concentration of the solutions with
respect to zinc, the greater will be the difference of the potential at the
two electrodes, or the greater will be the E.M.F. of the cell. When the
concentration of the two solutions becomes the same, the E.M.F. will become
zero, and no current will pass.
It will be understood now how this method can be made use of {338} for
determining the transition point of a salt, when we bear in mind that at
the transition point the solubility of the two forms becomes identical.
Thus, for example, the transition point of zinc sulphate heptahydrate into
hexahydrate could be determined in the following manner. Tube A (Fig. 134)
contains, say, a saturated solution of the heptahydrate along with some of
the solid salt; tube B, a saturated solution of the hexahydrate along with
the solid salt. The tube C is a connecting tube bent downwards so as to
prevent the mixing of the solutions by convection currents. ZZ are two zinc
electrodes immersed in the solution; the cell is placed in a thermostat and
the zinc electrodes connected with a galvanometer. Since, now, at
temperatures below the transition point the solubility of the hexahydrate
(the metastable form) is greater than that of the heptahydrate, a current
will be produced, flowing in the cell from heptahydrate to hexahydrate. As
the temperature is raised towards the transition point, the solubilities of
the two hydrates also approach, and the current produced will therefore
become weaker, because the E.M.F. of the cell becomes less; and when the
transition point is attained, the E.M.F. becomes zero, and the current
ceases. If the temperature is raised above this, the solubility of the
heptahydrate becomes greater than that of the hexahydrate, and a current
will again be produced, but in the opposite direction. By noting the
temperature, therefore, at which the current ceases, or the E.M.F. becomes
zero, the transition temperature can be ascertained.[406]
[Illustration: FIG. 134.]
In the case just described, the electrodes consisted of the same metal as
was contained in the salt. But in some cases, _e.g._ sodium sulphate,
electrodes of the metal contained in the salt cannot be employed.
Nevertheless, the above electrical method can be used {339} even in those
cases, if a suitable non-polarizable mercury electrode is employed.[407]
Although, as we saw, no current was produced when two pieces of zinc were
immersed in the same solution of zinc salt, a current will be obtained if
two different metals, or even two different modifications of the same
metal, are employed. Thus an E.M.F. will be established when electrodes of
grey and of white tin are immersed in the same solution of zinc salt, but
at the transition point this E.M.F. will become zero. By this method Cohen
determined the transition point of grey and white tin (p. 42).
* * * * *
{340}
NAME INDEX
A
Abegg, 52
Adriani, 186, 217, 220
Alexejeff, 97, 125
Allan, 298
Allen, L. E., 109
Allen, R. W., 63
Ampolla, 213
Andreae, 109
Aristotle, 41
Armstrong, E. F., 313
Armstrong, H. E., 196
Arzruni, 33
Aten, 147, 163
Auerbach, 326
B
Babo, 126
Bancroft, 102, 104, 161, 176, 196, 202, 229, 246, 260, 261, 272, 281, 302
Barnes, 331, 339
Barschall, 318
Barus, 67
Battelli, 23
Baur, 233, 307
Beckmann, 49
Bell, 229
Berthollet, 7
Bodlaender, 181, 247, 311, 321
Bogojawlenski, 72
Boudouard, 309, 311
Braun, 107
Brauns, 40, 51, 74
Bredig, 52
Bremer, 91
Brodie, 34, 47
Bruner, 126
Bruni, 181, 182, 256, 257
Bunsen, 67
C
Cady, 192
Calvert, 130
Cameron, 203
Carnelley, 47
Carpenter, 225
Carveth, 204, 255
Centnerszwer, 158
Chapman, 47
Chappuis, 51, 176
Charpy, 255
Churchill, 140
Coehn, 52
Cohen, 41, 72, 136, 139, 140
Cooke, 331, 339
Cox, 301
D
Dawson, 263
Debray, 74, 81, 139
Deville, 49, 74
Dewar, 26, 51, 178
Dietz, 157
{341}
Doelter, 233
Donnan, 8, 18
Dreyer, 73
Duhem, 56, 151
Dutoit, 204
E
Etard, 115, 135
F
Fahrenheit, 30
Faraday, 82, 89
Fath, 204
Fedotieff, 315, 320
Findlay, 111, 204, 206, 219
Foote, 69
Friedlaender, 72
Fritsche, 41
Frowein, 91
Fuechtbauer, 75
Fyffe, 143
G
Gattermann, 51, 52
Gautier, 222, 223
Gay-Lussac, 135
Gernez, 72
Gibbs, 7, 8, 151, 236
Glaessner, 307
Goldschmidt, E., 41
Goldschmidt, H., 335
Goldschmidt, V., 32
Goossens, 26
Gossner, 318
Graham, 178
Guertler, 73
Guldberg, 7
Guthrie, 97, 104, 117, 118, 119, 233
H
Haber, 311
Hahn, 309, 311
Hallock, 35
Hammerl, 145
Hautefeuille, 46, 49, 50, 51, 178
Heller, 311
Henry, 94
Herold, 321
Hertz, 49
Heycock, 194, 221, 223
Heyn, 225, 228
Hickmans, 219
Hiorns, 228
Hissink, 115, 190
Hoitsema, 14, 90, 177, 178, 298
Hollmann, 204
Holsboer, 110
Horstmann, 8, 83, 89
Hudson, 102
Hulett, 10, 48, 52, 54, 67, 109
I
Isaac, 114
Isambert, 80, 82, 84
J
Jaffe, 74, 114
Joulin, 176
Juhlin, 23, 24, 30
von Jueptner, 225
K
Kastle, 71
Kaufler, 49
Kaufmann, 112
Kayser, 176
Keeling, 225
Kelvin, 25
Kenrick, 263, 297
Kipping, 219
Kirchhoff, 32
Knorr, 203
de Kock, 53, 182, 194
Konowaloff, 102, 103, 104
Krasnicki, 144
Kremann, 147, 212
Kuenen, 105
Kultascheff, 233
{342}
Kuriloff, 216
Kurnakoff, 221, 222, 230
Kuester, 72, 181, 183
L
Laar, 195
Labenburg, 216
Lattey, 101
Le Chatelier, 58, 81, 233
Lehfeldt, 338, 340
Lehmann, 33, 52, 53
Lidbury, 147
Loewel, 134, 135
Loewenherz, 134, 316
Lowry, 196, 198
Ludwig, 327
Lumsden, 80, 109, 110
Lussana, 68
Luther, 22
M
Mack, 67
Magnus, 22
Mathews, 221
Mellor, 80
Meusser, 142
Meyer, J., 71
Meyer, V., 47
Meyerhoffer, 158, 233, 259, 268, 271, 278, 279, 280, 284, 313, 315, 317,
319, 327, 328, 336, 337
Middelberg, 116
Miers, 114
Miller, 297
Mitscherlich, 33, 49
Mond, 178
Moore, 72
Moss, 66
Mueller, 112, 265
Mylius, 109, 142, 157
N
Naumann, 49
Neville, 194, 221, 223
O
Offer, 119
Ostwald, 8, 10, 13, 16, 22, 44, 58, 68, 70, 74, 85, 88, 92, 102, 110,
117, 125, 127, 130, 141, 198
P
Padoa, 73, 181
Parsons, 298
Pasteur, 266
Paterno, 213
Payen, 74
Pedler, 47
Pfaundler, 119
Philip, 213, 214
von Pickardt, 73
Planck, 68
Pope, 219
Poynting, 68
Preuner, 311
Puschin, 222
Q
Quincke, 52
R
Rabe, 113
Ramsay, 3, 22, 23, 24, 30, 32, 63, 64, 66, 79, 90, 165, 178
Raoult, 180
Reed, 71
Regnault, 22
Reicher, 36, 37, 110, 260, 333
Reinders, 71, 185, 188
Reinitzer, 51, 52
Richards, 136, 140
Riddle, 47
Riecke, 48, 55
Roberts-Austen, 63, 194, 221, 223, 225
Roloff, 117
Roozeboom, 10, 38, 45, 47, 49, 50, 51, 54, 56, 57, 62, 63, 68, 88, 103,
126, 145, 147, 150, 151, 157, 162, 170, 174, 178, 182, 196, 201, 211,
217, 220, 225, 236, 238, 262, 264, 269, 272, 273, 281, 282, 290, 331
{343}
Rose, 223
Rotarski, 52
Rothmund, 97, 98, 100
Rutten, 298
S
Saposchnikoff, 212
Saunders, 313, 317, 319, 336, 337
Saurel, 151
Schaum, 49, 75
Scheel, 22, 23, 30
Schenck, 49, 52, 54, 311
Schneider, 52
Schoenbeck, 75
Schreinemakers, 122, 126, 246, 248, 250, 252, 290, 302
Schroetter, 46
Schukowsky, 52
Schwarz, 331
Seitz, 52
Shenstone, 109, 115, 135
Shepherd, 221, 255
Shields, 178
Skirrow, 130
Spring, 63
von Stackelberg, 107, 110
Staedel, 267
Stansfield, 194, 221
Stokes, 236
Stortenbeker, 44, 147, 161, 164, 281
T
Taber, 229
Tammann, 26, 32, 33, 37, 38, 39, 48, 52, 65, 67, 68, 72, 73, 140, 151,
176, 221, 230
Thiesen, 22, 23, 30
Thomson, J., 25, 28, 32
Thomson, W., 25
Tilden, 109, 115, 135
Trevor, 16
Troost, 46, 49, 50, 51
Tumlirz, 72
V
Van Bemmelen, 180
Van Deventer, 110, 139, 266, 267, 333
Van Eyk, 41, 63, 192, 338
Van't Hoff, 36, 38, 58, 70, 90, 92, 108, 127, 139, 140, 165, 175, 225,
258, 260, 263, 265, 266, 267, 272, 284, 290, 313, 318, 333, 340
Van Leeuwen, 259
Van Wyk, 185
Vogt, 5, 233
W
Waage, 7
Wald, 92
Walden, 158
Walker, 80, 105, 122, 126, 143
Wegscheider, 10, 49, 202
Wells, 136
Wenzel, 7
Wiebe, 22
Witt, 327
Wright, 241, 246, 247
von Wrochem, 109, 142
Y
Young, 3, 22, 23, 24, 30, 32, 63, 64, 66, 79, 105, 165
Z
Zacharias, 180
Zawidski, 63
Zenghelis, 35
Zimmermann, 311
Zincke, 44
Ziz, 141
* * * * *
{344}
SUBJECT INDEX
A
Acetaldehyde and paraldehyde, 204
Acetic acid, chloroform, water, 241
Acetone, phenol, water, 248
Adsorption, 176
Alcohol, chloroform, water, 246
----, ether, water, 246
Alloys, equilibrium curves of, 221
---- of copper and tin, liquefaction of, by cooling, 194
---- of iron and carbon, 223
---- of thallium and mercury, 222
----, ternary, 246
Ammonia compounds of metal chlorides, 82
Ammonia silver chlorides, 82
---- ---- ----, dissociation pressures of, 84
Ammonia-soda process, 320
Ammonium chloride, dissociation of, 3, 79
---- cyanide, dissociation of, 80
---- hydrosulphide, dissociation of, 80
---- nitrate, solubility of, 113
Aniline, phenol, water, 250
Astracanite, 260, 261, 268, 274
B
Babo, law of, 126
Barium acetate, solubility of, 143
Barium carbonate and potassium sulphate, 328
---- nitrite, preparation of, 327
Basic salts, 296
Benzaldoximes, 203
Benzene and picric acid, 216
Bismuth, effect of pressure on the melting point of, 67
----, lead, tin, 255
---- nitrates, basic, 298
Bivariant systems, 16
Bromocinnamic aldehyde and chlorocinnamic aldehyde, 183
C
Calcium carbonate, dissociation of, 3, 11, 81
---- chloride hexahydrate, solubility of, 146
---- ----, solubility of hydrates of, 148
---- ----, vapour-pressure of hydrates of, 88
Camphor oximes, 219, 257
Carnallite, 284
Carvoximes, 186, 219
Cementite, 224
Chlorine and iodine, 161
Chlorocinnamic aldehyde and bromocinnamic aldehyde, 183
Chloroform, acetic acid, water, 241
----, alcohol, water, 246
{345}
Classification of systems, 17
Component, 8, 10, 12
----, systems of one, 21, 55
Components, choice of, 12, 13, 14, 76, 313
----, determination of number of, 13
----, systems of four, 312
----, ---- of three, 234
----, ---- of two, 76, 207
----, variation in number of, 11, 14
Composition, determination of, without analysis, 228, 302
Concentration-temperature curve for two liquids, 101
Condensed systems, 36
Constituent, 10
Cooling curve, 230
Copper calcium acetate, 260
---- chloride, heat of solution of, 110
---- dipotassium chloride, 259
---- sulphate, 85
Critical concentration, 98, 242
---- pressure of water, 23
---- solution temperature, 98
---- temperature of water, 23
Cryohydrates, 117, 118
Cryohydric point, 117
---- ----, changes at the, 119
---- ---- for silver nitrate and ice, 116
Crystals, liquid, 51
----, ----, equilibria of, 53
----, ----, list of, 54
----, ----, nature of, 52
----, mixed, 180
Crystallization, velocity of, 72, 74
----, spontaneous, 114
D
Deliquescence, 130
Devitrification, 73
Diethylamine and water, solubility of, 101
Dilatometer, determination of transition points by, 331
Dineric surface, 247
Dissociation equilibrium, effect of addition of dissociation products on,
4
---- of ammonia compounds of metal chlorides, 82, 84
---- of ammonium chloride, 3, 79
---- ---- cyanide, 80
---- ---- hydrosulphide, 80
---- of calcium carbonate, 3, 81
---- of compounds, degree of, 147
---- of phosphonium bromide, 80
---- of salt hydrates, 85
----, phenomena of, 79
Dissociation pressure, 81
Distillation of supercooled liquid to solid, 32, 50
Double salt interval, 278
---- salts, crystallization from solution, 280
---- ----, decomposition by water, 267
---- ----, formation of, 258, 273, 315
E
Efflorescence, 86
Electrical methods of determining transition points, 338
Enantiotropy, 44, 51
Equilibria, Gibbs's theory of, 8
----, metastable, 69
Equilibrium apparent (false), 5, 6
---- between ice and solution, 116
---- between ice and water, 25
---- between ice, water, vapour, 27
---- between water and vapour, 21
----, chemical, 3, 16
----, heterogeneous, 5
----, homogeneous, 5
----, independence of, on amounts of phases, 9
----, law of movable, 58
{346}
----, physical, 3, 16
---- real (true), 5, 6
Ether, alcohol, water, 246
----, succinic nitrile, water, 252
Ethylene bromide, picric acid, [beta]-naphthol, 256
Eutectic mixtures, 117, 191, 209, 255, 257
---- point, 117, 209, 213, 253
F
Ferric chloride, evaporation of solutions of, 155
---- ----, hydrates of, 151, 153
---- ----, hydrogen chloride and water, systems of, 290
Ferrite, modifications of, 224
Freedom, degree of, 14
Freezing mixtures, 120
---- point, natural, 198
Fusion curve, 66
---- ---- of ice, 25
---- of ice, influence of pressure on, 26
----, partial, 139
G
Glaserite, 315, 317
Glasses, 176
Glauber's salt, 13, 134
---- ----, transition curve of, 68, 140
Graphic representation in space, 77, 284
H
Hydrates, range of existence of, 89
---- chloride and water, 174
Hydrogen bromide and water, 174
Hylotropic substances, 198
I
Ice I., 32
---- II., 32
---- III., 32
----, equilibrium between water and, 25
----, influence of pressure on melting point of, 25, 26
----, sublimation curve of, 24
----, vapour pressure of, 25, 31
Indifferent point, 150
Individual, chemical, 92
Inversion temperature, 36
Iodine and chlorine, 161
Iron--carbon alloys, 223
----, carbon monoxide and carbon dioxide, 305
Isomerides, dynamic, 195, 196
----, ----, equilibrium between, 195, 196
----, ----, equilibrium point of, 198
----, transformation of unstable into stable, 201
Isomerism, dynamic, 196
Isothermal evaporation, 278
---- solubility curves, 272
L
Lead, bismuth, tin, 255
----, desilverization of, 247
----, silver, zinc, 246
Le Chatelier, theorem of, 57
Lime, burning of, 3
Liquidus curve, 182
M
Mandelic acid, 217
Martensite, 224
Mass action, law of, 7
Melting point, influence of pressure on, 66
{347}
---- ----, congruent, 146
---- ----, incongruent, 139
---- under the solvent, 122
Menthyl mandelates, 219
Mercuric bromide and iodide, 188
Mercury salts, basic, 301
Metastable equilibria, 69
---- region, 30
---- state, 30
Methylethyl ketone and water, 100
Minerals, formation of, 232
Miscibility of liquids, complete, 95, 104, 114
---- ----, partial, 95, 96, 121
Mixed crystals, 180, 281
---- ----, changes in, with temperature, 192
---- ----, examples of, 183, 186, 187, 190, 192, 219, 223
---- ----, formation of, 181, 182
---- ----, fractional crystallization of, 188
---- ----, freezing points of, 182
---- ----, melting points of, 182, 184
---- ----, pseudoracemic, 219
Mixtures, isomorphous, 181
---- of constant boiling point, 105
---- of constant melting point, 117, 186, 187, 192, 209, 255, 257
Monotropy, 44, 51
Multivariant systems, 16
N
Naphthalene and monochloracetic acid, 192
---- and [beta]-naphthol, mixed crystals of, 183
[beta]-Naphthol, ethylene bromide, picric acid, 256
[alpha]-Naphthylamine and phenol, 213
Nickel iodate, solubility of, 142
_o_-Nitrophenol and _p_-toluidine, 213
O
Occlusion of gases, 176
Optical method of determining transition points, 338
Optically active substances, freezing-point curves of, 216
Order of a system, 13
Organic compounds, application of Phase Rule to, 212
P
Palladium and hydrogen, 90, 178
Paragenesis, 320
Paraldehyde and acetaldehyde, 204
Partial pressures of two components, 102
Pearlite, 224
Phase, 8
---- Rule, 8, 16
---- ----, deduction of, 18
---- ----, scope of, 1
Phases, formation of new, 69
----, number of, 9
Phenol, acetone, water, 248
----, aniline, water, 250
---- and [alpha]-naphthylamine, 213
---- and _p_-toluidine, 214
---- and water, solubility of, 97
Phosphonium bromide, dissociation of, 80
---- chloride, 65
Phosphorus, 46
----, distillation of white to red, 50
----, melting point of red, 47
----, ---- ---- of white, 48
----, solubility of white and red, 47
----, vapour pressure of white and red, 46
Picric acid and benzene, 216
---- ----, ethylene bromide, and [beta]-naphthol, 256
Polymorphic forms, solubility of, 112
{348}
---- substances, list of, 63
Polymorphism, 33
Potassium nitrate and thallium nitrate, 192
Potential, chemical, 19
Pressure-concentration diagram for two liquids, 102
Pressure-temperature diagram for solutions, 126
Pseudomonotropy, 45
Pseudo-racemic mixed crystals, 21
Pyridine and methyl iodide, 147
Pyrometer, registering, 230
Q
Quadruple point, 116
Quintuple point, 234, 261
R
Racemates, characterization of, 217, 282
Reactions, law of successive, 73
Reciprocal salt-pairs, 313
---- ----, transition point of, 314
Rubidium tartrates, 265
S
Salt hydrates, 85
---- ----, indefiniteness of vapour pressure of, 87
---- ---- with definite melting point, 145
Separation of salt on evaporation, 130
Silicates, hydrated, 176
Silver, lead, zinc, 246
Silver nitrate, solubility of, 114
---- ---- and sodium nitrate, 190
Single salt interval, 278
Sodium ammonium tartrates, 266
---- nitrate and silver nitrate, 190
---- sulphate and water, equilibria between, 134
Sodium sulphate and water, vapour pressures of, 138, 140
---- ----, anhydrous, dehydration by, 138
---- ----, solubility of, 135
---- ---- decahydrate, solubility of, 134
---- ---- ----, transition point of, 136, 139
---- ---- heptahydrate, solubility of, 136
---- ---- ----, transition point of, 137
Solidus curve, 182
Solubility curve at higher temperatures, 114
---- ----, form of, 108
---- ---- of anhydrous salts, 111
---- ----, retroflex, 146, 151, 162
---- curves, interpolation and extrapolation of, 111
---- ---- of three component systems, 264
----, determination of transition points by, 335
----, influence of pressure on, 107
----, ---- of subdivision on, 10
----, ---- of temperature on, 109
---- of metastable forms, 47, 112, 137
Solubility of polymorphic forms, 112
---- of salt hydrates, 133, 145
---- of supercooled liquids, 125
----, retrograde, 245
Solute, 93
Solution, definition of, 92
----, heat of, 109, 110
----, saturated, 106, 108
----, supersaturated, 108
---- temperature, critical, 98
----, unsaturated, 108
Solutions, bivariant systems, 129
----, congruently saturated, 279
---- conjugate, 97, 241
{349}
----, incongruently saturated, 279, 289
----, inevaporable, 157
---- of gases in liquids, 93
---- ---- in solids, 176
---- of liquids in liquids (binary), 95
---- ---- ---- (ternary), 240
---- ----, influence of temperature on, 247
---- of solids in liquids, 106
---- ---- in solids, 180
----, solid, 175, 180
----, univariant systems, 127
Space model for carnallite, 284
Stability limit, 202
Steel, formation of, 223
Sublimation curve, 63
---- ---- of ice, 24
---- without fusion, 65
Succinic nitrile and water, 122
---- ether, water, 252
Sulphur, 33, 34
---- dioxide and water, 169
---- ---- and potassium iodide, 158
----, transition point of rhombic and monoclinic, 36
Supersaturation, 113, 114, 124
----, limits of, 114
Systems, condensed, 36
---- of one component, 21
---- of two components, 76, 77, 207
T
Tachydrite, influence of pressure on the transition point of, 263
Tartrate, dimethyl, 217
----, sodium potassium, 259
Tautomeric substances, 195
Tensimeter, 91
Thallium nitrate and potassium nitrate, 192
Theorem of van't Hoff and Le Chatelier, 57
Thermometric determination of transition point, 337
Tin, 41
----, lead, bismuth, 255
---- plague, 43
----, transition point of white and grey, 41
_p_-Toluidine and _o_-nitrophenol, 213
---- and phenol, 214
Transformation of optically active substances, 220
----, suspended, 37, 69, 89, 113, 137, 155
----, velocity of, 70
Transition curve, 66
---- ---- of Glauber's salt, 68, 140
---- ---- of rhombic and monoclinic sulphur, 37
---- interval, 270, 277, 315
---- point, 34
---- ---- for double salts, 258
---- ----, influence of pressure on the, 68
---- points, as fixed points in thermometry, 140
---- ----, methods of determining, 331
---- ---- of polymorphic substances, 63
Triangle, graphic representation by, 235
Triethylamine and water, 101
Triple point, 27, 55
---- ----, arrangement of curves round, 56
---- ----, changes at, 58
---- ----, ice, water, vapour, 27
---- ----, ice II., ice III., and water, 33
---- ----, metastable, 38
---- ----, monoclinic sulphur, liquid, vapour, 38
---- ----, monoclinic and rhombic sulphur, liquid, 38
---- ----, monoclinic and rhombic sulphur, vapour, 34
{350}
---- ----, red phosphorus, liquid, vapour, 47
---- ----, rhombic sulphur, liquid, vapour, 38
---- ---- solid, solid, vapour, 62
---- ----, white phosphorus, liquid, vapour, 48
U
Univariant systems, 16
V
Van't Hoff, theorem of, 57
Vaporization curve, 63
---- ----, interpolation and extrapolation of, 66
---- ---- of water, 21, 23
Vapour pressure, constancy of, and formation of compounds, 90
---- ----, dependence of, on solid phase, 88
---- ----, influence of surface tension on, 2
---- ---- in three-component systems, 261
---- ----, measurement of, 91, 334
---- ---- of calcium chloride solutions, 150
---- ---- of ice, 25, 31
---- ---- of small drops, 10
---- ---- of sodium sulphate and water, 138
Vapour pressure of solid, solution, vapour, 126
---- ---- of water, 21, 31
Variability of a system, 14, 16
Variance of a system, 16
Volatile components, two, 161
W
Water, 21
----, acetic acid, chloroform, 241
----, acetone, phenol, 248
----, alcohol, ether, 246
----, ----, chloroform, 246
----, aniline, phenol, 250
----, bivariant systems of, 29
----, critical pressure of, 23
----, critical temperature of, 23
----, equilibrium between ice and, 25
----, ---- between vapour and, 21
----, ether, succinic nitrile, 252
----, supercooled, 30
----, ----, vapour pressure of, 31
----, vaporization curve of, 21
----, vapour pressure of, 23
Z
Zeolites, 176
Zinc, lead, silver, 246
---- chloride in water, solubility of, 157
THE END
PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES.
* * * * *
NOTES
[1] Except when the volume of the liquid becomes exceedingly small, in
which case the surface tension exerts an influence on the vapour pressure.
[2] For reasons which will appear later (Chap. IV.), the volume of the
vapour is supposed to be large in comparison with that of the solid and
liquid.
[3] Ramsay and Young, _Phil. Trans._, 1886, 177. 87.
[4] See, more especially, Vogt, _Die Silikatschmelzloesungen_.
(Christiania, 1903, 1904.)
[5] _Trans. Connecticut Acad._, 1874-1878.
[6] Lehre von der chemischen Verwandtschaft der Koerper, 1777.
[7] See Ostwald's _Klassiker_, No. 74.
[8] Etudes sur les affinites chimiques, 1867; Ostwald's _Klassiker_, No.
104.
[9] Died April, 1903.
[10] For a mathematical treatment of the Phase Rule the reader is referred
to the volume in this series on Thermodynamics, by F. G. Donnan.
[11] Liebig's _Annalen_, 1873, 170, 192; Ostwald, _Lehrbuch_, II. 2. 111.
[12] The action of gravity and other forces being excluded (see p. 5).
[13] It may seem as if this were a contradiction to what was said on p. 4
as to the effect of the addition of ammonia or hydrogen chloride to the
system constituted by solid ammonium chloride in contact with its products
of dissociation. There is, however, no contradiction, because in the case
of ammonium chloride the gaseous phase consists of ammonia and hydrogen
chloride in equal proportions, and in adding ammonia or hydrogen chloride
alone we are not adding the gaseous phase, but only a constituent of it.
Addition of ammonia and hydrogen chloride together in the proportions in
which they are combined to form ammonium chloride would cause no change in
the equilibrium.
[14] The vapour pressure of water in small drops is greater than that of
water in mass, and the solubility of a solid is greater when in a state of
fine subdivision than when in large pieces (_cf._ Hulett, _Zeitschr.
physikal. Chem._, 1901, 37. 385).
[15] See Ostwald, _Lehrbuch_, II. 2. 476, 934; Roozeboom, _Zeitschr.
physikal. Chem._, 1894, 15. 150; _Heterogene Gleichgewichte_, I. p. 16;
Wegscheider, _Zeitschr. physikal. Chem._, 1903, 43. 89.
[16] Ostwald, _Lehrbuch_, II. 2. 478.
[17] See also Hoitsema, _Zeitschr. physikal. Chem._ 1895, 17. 651.
[18] The term "degree of freedom" employed here must not be confused with
the same term used to denote the various movements of a gas molecule
according to the kinetic theory.
[19] Trevor, _Jour. Physical Chem._, 1902, 6. 136.
[20] Ostwald, _Principles of Inorganic Chemistry_, translated by A.
Findlay, 2nd edit., p. 7. (Macmillan, 1904.)
[21] See the volume in this series on _Thermodynamics_ by F. G. Donnan.
[22] _Pogg. Annalen_, 1844, 61. 225.
[23] _Memoires de l'Acad._, 26. 751.
[24] _Phil. Trans._ 1884, 175. 461; 1892, A, 183. 107.
[25] _Bihang Svenska Akad. Handl._ 1891, 17. I. 1.
[26] Abh_andl. physikal.-tech. Reichsanstalt_, 1900, 3. 71.
[27] Ostwald-Luther, _Physiko-chemische Messungen_, 2nd edit., p. 156.
[28] _Annales chim. et phys._, 1892 [6], 26. 425.
[29] The vapour pressure of water at 0deg has recently been very accurately
determined by Thiesen and Scheel (_loc. cit._), and found to be 4.579 +/-
0.001 mm. of mercury (at 0deg), or equal to 0.006025 atm.
[30] Juhlin, _Bihang Svenska Akad. Handl._, 1891, 17. I. 58. See also
Ramsay and Young, _loc. cit._
[31] _Trans. Roy. Soc. Edin._, 1849, 16. 575.
[32] _Proc. Roy. Soc. Edin._, 1850, 2, 267.
[33] _Annalen der Physik_, 1899 [3], 68. 564; 1900 [4], 2. 1, 424. See
also Dewar, _Proc. Roy. Soc._, 1880, 30. 533.
[34] The pressure of 1 atmosphere is equal to 1.033 kilogm. per sq. cm.; or
the pressure of 1 kilogm. per sq. cm. is equal to 0.968 atm.
[35] Tammann, _loc. cit._, 1900, 2. 1, 424; cf. Goossens, _Arch. neerland_,
1886, 20. 449.
[36] J. Thomson, _Proc. Roy. Soc._, 1874, 22. 28.
[37] A field is "enclosed" by two curves when these cut at an angle less
than two right angles. It may be useful to remember that an invariant
system is represented by a _point_, a univariant system by a _line_, and a
bivariant system by an _area_.
[38] _Phil. Trans._, 1724, 39. 78.
[39] Juhlin, _loc. cit._, p. 61; cf. Ramsay and Young, _loc. cit._: Thiesen
and Scheel, _loc. cit._
[40] This small difference is due to experimental errors in the
determination of the vapour pressures; a differential method betrayed no
difference between the vapour pressure of ice and of water at 0deg.
[41] _Phil. Mag._, 1874 [4], 47. 447; _Proc. Roy. Soc._, 1873, 22. 27.
[42] _Pogg. Annalen_, 1858, 103, 206.
[43] See _Phil. Trans._, 1884, 175, 461.
[44] This phenomenon of distillation from the supercooled liquid to the
solid has been very clearly observed in the case of furfuraldoxime (V.
Goldschmidt, _Zeitschr. f. Krystallographie_, 1897, 28. 169).
[45] _Annalen der Physik_, 1900 [4], 2. 1, 424.
[46] A similar triple point has been determined by Tammann in the case of
phenol (_Annalen der Physik_, 1902 [4], 9. 249).
[47] _Annales chim. et phys._, 1821, 19. 414.
[48] Lehmann, _Molekularphysik_, I. 153.; Arzruni, _Physikalische Chemie
der Krystalle_. (Graham-Otto, _Lehrbuch der Chemie_, I. 3.)
[49] Brodie, _Proc. Roy. Soc._, 1855, 7. 24.
[50] That solid sulphur does possess a certain vapour pressure has been
shown by Hallock, who observed the formation at the ordinary temperature of
copper sulphide in a tube containing copper and sulphur (_Amer. Jour.
Sci._, 1889 [3], 37. 405). See also Zenghelis, _Zeitschr. physikal.
Chem._, 1904, 50. 219.
[51] _Zeitschr. fuer Krystallographie_, 1884, 8. 593.
[52] Van't Hoff, _Studies on Chemical Dynamics_, p. 163.
[53] Reicher, _loc. cit._ See also Tammann, _Annalen der Physik_, 1899
[3], 68. 663.
[54] Tammann, _Annalen der Physik_, 1899 [3], 68. 633.
[55] Rec. Trav. _Chim. Pays-Bas_, 1887, 6. 314.
[56] Cf. van't Hoff, _Lectures on Physical Chemistry_, I., p. 27 (Arnold).
[57] _Annalen der Physik_, 1899 [3], 68. 663.
[58] Brauns, _Jahrbuch fuer Mineralogie_, 1899-1901, 13. Beilage, p. 39.
[59] Fritsche, _Ber._, 1869, 2. 112, 540.
[60] _De mirabilibus Auscultationibus_, Cap. 51 (_v._ Cohen, _Zeitschr.
physikal. Chem._, 1901, 36. 513).
[61] E. Cohen and C. van Eyk, _Zeitschr. physikal. Chem._, 1899, 30. 601;
Cohen, _ibid._, 1900, 33. 59; 35. 588; 1901, 36. 513; Cohen and E.
Goldschmidt, _ibid._, 1904, 50. 225.
[62] _Zeitschr. physikal. Chem._, 1900, 33, 58.
[63] Stortenbeker, _Zeitschr. physikal. Chem._, 1889, 3. 11; _Rec. Trav.
Chim. Pays-Bas_, 1888, 7. 152.
[64] Zincke, _Ber._, 1871, 4. 576.
[65] Ostwald, _Zeitschr. physikal. Chem._, 1897, 22. 313.
[66] Roozeboom, _Das Heterogene Gleichgewicht_, I. p. 177.
[67] Roozeboom, _ibid._, p. 179.
[68] Schroetter, _Pogg. Annalen_, 1850, 81. 276; Troost and Hautefeuille,
_Annales de Chim. et Phys._ 1874 [5], 2. 153; _Ann. Scient. Ecole Norm._
1868 [2], II. 266.
[69] Pedler, _Trans. Chem. Soc._, 1890, 57. 599.
[70] Brodie, _Trans. Chem. Soc._, 1853, 5, 289.
[71] This is a familiar fact in the case of the solubility in carbon
disulphide.
[72] Roozeboom, _Das Heterogene Gleichgewicht_, I. p. 170.
[73] _Trans. Chem. Soc._, 1899, 57. 734.
[74] Carnelley, _Trans. Chem. Soc._, 1876, 29. 489; 1878, 33. 275. V. Meyer
and Riddle, _Ber._, 1893, 26. 2443.
[75] Riecke, _Zeitschr. physikal. Chem._, 1890, 6. 411.
[76] _Annalen der Physik._, 1898 [3], 66. 492.
[77] _Zeitschr. physikal. Chem._, 1899, 28. 666.
[78] See Naumann, _Ber._, 1872, 4. 646; Troost and Hautefeuille, _Compt.
rend._, 1868, 66. 795; 1868, 67. 1345; Roozeboom, _Das Heterogene
Gleichgewicht_, I. pp. 62, 171.
[79] Mitscherlich, _Lieb. Annalen_, 1834, 12. 137; Deville and Troost,
_Compt. rend._, 1863, 56. 891.
[80] Beckmann, _Zeitschr. physikal. Chem._, 1890, 5. 79; Hertz, _ibid._, 6.
358.
[81] _Ber._, 1902, 35. 351. _Cf._ also, K. Schaum, _Annalen der Chem._,
1898, 300. 221; R. Wegscheider and Kaufler, _Sitzungsber. kaiserl. Akad.
Wissensch. in Wien_, 1901, 110, II. 606.
[82] See also Roozeboom, _Das Heterogene Gleichgewicht_, I. p. 177.
[83] _Annales de Chim. et Phys._, 1874 [5], 2. 154.
[84] _Compt. rend._, 1887, 104. 1505.
[85] _Compt. rend._, 1868, 66. 795.
[86] _Phil. Mag._, 1884 [5], 18. 210. See also Roozeboom, _Das Heterogene
Gleichgewicht_, I. p. 177.
[87] Brauns, _Neues Jahrbuch fuer Mineralogie_, 1900, 13. Beilage-Band, p.
39; Roozeboom, _Das Heterogene Gleichgewicht_, I. p. 181.
[88] _Monatshefte_, 1888, 9. 435.
[89] Gattermann, _Ber._, 1890, 53. 1738.
[90] _Zeitschr. physikal. Chem._, 1889, 4. 468; _Annalen der Physik_, 1900
[4], 2. 649.
[91] Quincke, _Annalen der Physik_, 1894 [3], 53. 613; Tammann, _Annalen
der Physik_, 1901 [4], 4. 524; 1902, 8. 103; Rotarski, _ibid._, 4. 528.
[92] _Annalen der Physik_, 1900 [4], 2. 649.
[93] _Annalen der Physik_, 1902 [4], 8. 911.
[94] See, more especially, O. Lehmann, _Annalen der Physik_, 1900 [4], 2.
649; Reinitzer, _Sitzungsber. kaiserl. Akad. zu Wien._, 1888, 94. (2), 719;
97. (1), 167; Gattermann, _loc. cit._; Schenck, _Zeitschr. physikal.
Chem._, 1897, 23. 703; 1898, 25. 337; 27. 170; 1899, 28. 280; Schenck and
Schneider, _ibid._, 1899, 29. 546; Abegg and Seitz, _ibid._, 1899, 29. 491;
Hulett, _ibid._, 1899, 28. 629; Coehn, _Zeitschr. Elektrochem._, 1904, 10.
856: Bredig and Schukowsky, _ibid._, 3419. For a full account of the
subject, the reader is referred to the work by Lehmann, _Fluessige
Kristalle_ (Engelmann, 1904), or the smaller monograph by Schenck,
_Kristallinische Fluessigkeiten und fluessige Kristalle_ (Engelmann, 1905).
[95] A. C. de Kock, _Zeitschr. physikal. Chem._, 1904, 48. 129.
[96] On account of the fact that all grades of rigidity have been realized
between the ordinary solid and the liquid state, in the case both of
crystalline and amorphous substances, it has been proposed to abandon the
terms "solid" and "liquid," and to class bodies as "crystalline" or
"amorphous," the passage from the one condition to the other being
discontinuous; crystalline bodies possess a certain regular orientation of
their molecules and a directive force, while in amorphous bodies these are
wanting (see Lehmann, _Annalen der Physik_, 1900 [4], 2. 696).
[97] Hulett, _loc. cit._
[98] Roozeboom, _Das Heterogene Gleichgewicht_, I. p. 144. See also
Schenck, _Kristallinische Fluessigkeiten und fluessige Kristalle_, p. 8
(Engelmann, 1904).
[99] The possible number of triple points in a one-component system is
given by the expression (_n_(_n_ - 1)(_n_ - 2))/1.2.3, where _n_ is the
number of phases (Riecke, _Zeitschr. physikal. Chem._, 1890, 6, 411). The
number of triple points, therefore, increases very rapidly as the number of
possible phases increases.
[100] Duhem, _Zeitschr. physikal. Chem._, 1891, 8. 371. _Cf._ Roozeboom,
_Das Heterogene Gleichgewicht_, p. 94 ff.
[101] Roozeboom, _Das Heterogene Gleichgewicht_, I. p. 99.
[102] Roozeboom, _Zeitschr. physikal. Chem._, 1888, 2. 474.
[103] These changes can be predicted quantitatively by means of the
thermodynamic equation, _dp_/_dt_ = Q/(T(_v_{2}_ - _v_{1}_)), provided the
specific volumes of the phases are known, and the heat effect which
accompanies the transformation of one phase into the other.
[104] _Studies on Chemical Dynamics_, translated by Ewan, p. 218.
[105] Le Chatelier, _Compt. rend._, 1884, 99. 786.
[106] See _Principles of Inorganic Chemistry_, translated by Findlay, 2nd
edit., p. 133. (Macmillan, 1904.)
[107] Roozeboom, _Zeitschr. physikal. Chem._, 1888, 2. 474.
[108] Roozeboom, _Das Heterogene Gleichgewicht_, I. p. 189.
[109] Roozeboom, _Das Heterogene Gleichgewicht_, I. p. 125. See also
Zawidski, _Zeitschr. physikal. Chem._, 1904, 47. 727; van Eyk, _ibid._,
1905, 51. 720.
[110] Roberts-Austen, _Proc. Roy. Soc._, 63. 454; Spring, _Zeitschr.
physikal. Chem._, 1894, 15. 65. See also p. 35.
[111] Ramsay and Young, _Phil. Trans._, 1884, 175. 461; Allen, _Trans.
Chem. Soc._, 1900, 77. 413.
[112] Ramsay and Young, _Phil. Trans._ 1886, 177. 87.
[113] This is exemplified in the well-known experiment with the cryophorus.
[114] Tammann has, however, found that the fusion curve (solid in contact
with liquid) of phosphonium chloride can be followed up to temperatures
above the critical point (_Arch. neer._, 1901 [2], 6. 244).
[115] _Phil. Mag._, 1886, 21. 33. See also S. A. Moss, _Physical Review_,
1903, 16. 356.
[116] This is found also in the case of bismuth. See Tammann, _Zeitschr.
anorgan. Chem._, 1904, 40. 54.
[117] See p. 57, footnote.
[118] _Pogg. Annalen_, 1850, 81. 562.
[119] Barus, _Amer. Jour. Sci._, 1892, 42. 125; Mack, _Compt. rend._, 1898,
127. 361; Hulett, _Zeitschr. physikal. Chem._, 1899, 38. 629.
[120] _Annalen der Physik_, 1899 [3], 68. 553, 629; 1900 [4], 1. 275; 2.
1; 3. 161. See also Tammann, _Kristallisieren und Schmelzen_ (Leipzig,
1903).
[121] Ostwald, _Lehrbuch_, II. 2. 373; Poynting, _Phil. Mag._, 1881 [5],
12. 2; Planck, _Wied. Annalen_, 1882, 15. 446.
[122] Bakhuis Roozeboom, _Das Heterogene Gleichgewicht_, I. p. 91.
[123] Lussana, _Il nuovo Cimento_, 1895 [4], 1. 105.
[124] Tammann, _Zeitschr. physikal. Chem._, 1903, 46. 818.
[125] Foote, _Zeitschr. physikal. Chem._, 1900, 33. 740.
[126] Ostwald, _Zeitschr. physikal. Chem._, 1897, 22. 289.
[127] Van't Hoff, _Arch, neer._, 1901, 6. 471.
[128] See, for example, the determinations of the solubility of rhombic and
monoclinic sulphur, by J. Meyer, _Zeitschr. anorg. Chem._, 1902, 33. 140.
[129] _Zeitschr. physikal. Chem._, 1899, 32. 506.
[130] Kastle and Reed, _Amer. Chem. Jour._, 1902, 27. 209.
[131] _Zeitschr. physikal. Chem._, 1900, 35. 581.
[132] _Compt. rend._, 1882, 95. 1278; 1884, 97. 1298, 1366, 1433.
[133] _Zeitschr. physikal. Chem._, 1893, 12. 545.
[134] _Sitzungsber. Wiener Akad._, 1894, 103. IIa. 226.
[135] _Zeitschr. physikal. Chem._, 23-29. See also Kuester, _ibid._, 25-28.
[136] _Zeitschr. physikal. Chem._, 1897, 24. 152.
[137] _Ibid._, 1898, 27. 585.
[138] See W. Guertler, _Zeitschr. anorgan. Chem._, 1904, 40. 268; Tammann,
_Zeitschr. Elektrochem._, 1904, 10. 532.
[139] E. von Pickardt, _Zeitschr. physikal. Chem._, 1902, 42. 17.
[140] _Zeitschr. physikal. Chem._, 1904, 48. 467.
[141] M. Padoa, _Accad. Lincei, Atti_, 1904, 13. 329.
[142] Deville, _Compt. rend._, 1852, 34. 561; Payen, _ibid._, 1852, 34.
508; Debray, _ibid._, 1858, 46. 576. It has also been found by Jaffe
(_Zeitschr. physikal. Chem._, 1903, 43. 465) that when spontaneous
crystallization from solution occurs, the less stable form always separates
first when purification has been carried sufficiently far.
[143] Brauns, _Neues Jahrbuch fuer Mineralogie_, 1899, 13. (Beilage Band)
84.
[144] _Lehrbuch_, II. 2. 445. See also _Principles of Inorganic Chemistry_,
2nd edit., p. 210 ff.
[145] Schaum and Schoenbeck, _Annalen der Physik_, 1902 [4], 8. 652. See
also Chr. Fuechtbauer, _Zeitschr. physikal. Chem._, 1904, 48. 549.
[146] Ramsay and Young, _Phil. Trans._, 1886, 177. 87.
[147] See volume in this series on _Chemical Dynamics_, by Dr. J. W.
Mellor.
[148] Isambert, _Compt. rend._, 1881, 92. 919; 1882, 94. 958; 1883, 96.
643. Walker and Lumsden, _Jour. Chem. Soc._, 1897, 71. 428.
[149] _Compt. rend._, 1867, 64. 603.
[150] _Compt. rend._, 1883, 102. 1243.
[151] _Compt. rend._, 1868, 66, 1259.
[152] Horstmann, _Ber._, 1876, 9. 749.
[153] _Loc. cit._
[154] For the reasons for choosing anhydrous salt and water instead of salt
hydrate and water as components, see p. 14.
[155] See Ostwald, _Lehrbuch_, II. 2. 527.
[156] Ostwald, _Lehrbuch_, II. 2. 538.
[157] _Zeitschr. physikal. Chem._, 1889, 4. 43.
[158] _Ber._, 1876, 9. 749.
[159] See, for example, van't Hoff, _Lectures on Theoretical and Physical
Chemistry_, I. p. 62 (Arnold).
[160] _Jour. Chem. Soc._, 1877, 32. 395.
[161] Hoitsema, _Zeitschr. physikal. Chem._, 1895, 17. 1.
[162] _Zeitschr. physikal. Chem._, 1887, 1. 5; 1895, 17. 52.
[163] It is important to powder the salt, since otherwise the dehydration
of the hydrate and the production of equilibrium occurs with comparatively
great tardiness.
[164] A chemical individual is a substance which persists as a phase of
constant composition when the conditions of temperature, pressure, and
composition of the other phases present, undergo continuous alteration
within certain limits--the limits of existence of the substance (Wald,
_Zeitschr. physikal. Chem._, 1897, 24. 648).
[165] Van't Hoff, _Zeitschr. physikal. Chem._, 1890, 5. 323; Ostwald,
_Lehrbuch_, I. 606.
[166] That mercury does dissolve in water can be argued from analogy, say,
with mercury and bromonaphthalene. At the ordinary temperature these two
liquids appear to be quite insoluble in one another, but at a temperature
of 280deg the mercury dissolves in appreciable quantity; for on heating a
tube containing bromonaphthalene over mercury the latter sublimes _through_
the liquid bromonaphthalene and condenses on the upper surface of the tube.
[167] _Phil. Mag._, 1884, [5], 18. 22; 495.
[168] _Wied. Annalen_, 1886, 28. 305.
[169] _Zeitschr. physikal. Chem._, 1898, 26. 433.
[170] Rothmund, _loc. cit._
[171] Rothmund, _loc. cit._
[172] A similar behaviour is found in the case of diethylamine and water
(R. T. Lattey, _Phil. Mag._, 1905, [6], 10, 397).
[173] C. S. Hudson, _Zeitschr. physikal. Chem._, 1904, 47. 113.
[174] Konowaloff, _Wied. Annalen_, 1881, 14. 219. Ostwald, _Lehrbuch_, II.
2. 687. Bancroft, _Phase Rule_, p. 96.
[175] Konowaloff, _loc. cit._
[176] Roozeboom, _Zeitschr. physikal. Chem._, 1891, 8. 526; _Rec. Trav.
Chim. Pays-Bas_, 1884, 3. 38.
[177] Konowaloff, _loc. cit._ Cf. Bancroft, _Phase Rule_, p. 100.
[178] _Phil. Mag._, 1884 [5], 18. 503.
[179] See, for example, Walker, _Introduction to Physical Chemistry_, 3rd
edit., p. 86 (Macmillan, 1903). Consult also Young, _Fractional
Distillation_ (Macmillan, 1903), or Kuenen, _Verdampfung und Verfluessigung
von Gemischen_ (Barth, 1906), where the subject is fully treated.
[180] Since this is the only phase of variable composition present.
[181] E. von Stackelberg, _Zeitschr. physikal. Chem._, 1896, 20. 337. If
the change of volume which accompanies solution, and the heat effect are
known, the quantitative change of the solubility with the pressure can be
calculated (Braun, _Zeitschr. physikal. Chem._, 1887, 1. 259).
[182] Van't Hoff, _Arch. neerland._ 1901 [2], 6. 471.
[183] Tilden and Shenstone, _Phil. Trans._ 1884, 175. 23; Hulett and Allen,
_Jour. Amer. Chem. Soc._ 1902, 24. 667; Andreae, _Jour. prak. Chem._ 137.
474; Lumsden, _Jour. Chem. Soc._, 1902, 81. 350; Mylius and v. Wrochem,
_Ber._ 1900, 33. 3689.
[184] E. von Stackelberg, _Zeitschr. physikal. Chem._ 1896, 20. 159; 1898,
26. 533; Lumsden, _Jour. Chem. Soc._, 1902, 81. 350; Holsboer, _Zeitschr.
physikal. Chem._, 1902, 39. 691.
[185] Reicher and van Deventer, _Zeitschr. physikal. Chem._ 1890, 5. 559;
cf. Ostwald, _Lehrbuch_, II. 2. 803.
[186] It has been shown that the formula of Ramsay and Young (p. 66) can be
applied (with certain restrictions) to the interpolation and extrapolation
of the solubility curve of a substance provided two (or three) points on
the curve are known. In this case T, T_{1}, etc., refer to the temperatures
at which the two substances--one the solubility curve of which is known,
the other the solubility curve of which is to be calculated--have equal
solubilities, instead of, as in the previous case, equal vapour pressures.
(Findlay, _Proc. Roy. Soc._, 1902, 69. 471; _Zeitschr. physikal. Chem._,
1903, 42. 110.)
[187] W. Mueller and P. Kaufmann, _Zeitschr. physikal. Chem._ 1903, 42.
497.
[188] W. O. Rabe, _Zeitschr. physikal. Chem._, 1901, 38. 175.
[189] With regard to the limits of supersaturation and the spontaneous
crystallization of the solute from supersaturated solutions, see Jaffe,
_Zeitschr. physikal. Chem._, 1903, 43. 565, and the very interesting paper
by Miers and Isaac, _Trans. Chem. Soc._, 1906, 89. 413.
[190] _Annales chim. phys._, 1894 [7], 2. 524.
[191] _Phil. Trans._, 1884, 175. 23.
[192] Hissink, _Zeitschr. physikal. Chem._, 1900, 32. 543.
[193] _Zeitschr. physikal. Chem._, 1903, 43. 313.
[194] Guthrie, _Phil. Mag._, 1875, [4], 49. 1; 1884, [5], 17. 462.
[195] See Roloff, _Zeitschr. physikal. Chem._, 1895, 17. 325; Guthrie,
_loc. cit._
[196] Guthrie, _Phil. Mag._, _loc. cit._ Cf. Ostwald, _Lehrbuch_, II. 2.
843.
[197] Guthrie, _Phil. Mag._, 1875 [4], 49. 269.
[198] _Ber._, 1877, 20. 2223.
[199] _Silz-Ber. Wien. Akad._, 1880, 81. II. 1058.
[200] Guthrie, _Phil. Mag._, 1875 [4], 49. 206.
[201] If in the neighbourhood of the cryohydric point solution should be
accompanied by an evolution of heat, then as the solubility would in that
case increase with fall of temperature, salt would pass into solution.
[202] Walker, _Zeitschr. physikal. Chem._, 1890, 5. 193.
[203] _Zeitschr. physikal. Chem._, 1897, 23. 418.
[204] Provided the solid nitrile is not present in too great excess.
[205] _Wied. Annalen_, 1886, 28. 328. Cf. Ostwald, _Lehrbuch_, II. 2. 872.
[206] Walker, _Zeitschr. physikal. Chem._, 1890, 5. 193. Schreinemakers,
_ibid._, 1897, 23. 417. Roozeboom, _Rec. trav. chim. Pays-Bays_, 1889, 8.
257. Bruner, _Zeitschr. physikal. Chem._, 1897, 23. 542.
[207] Van't Hoff, _Lectures on Theoretical Chemistry_, I. p. 42. Ostwald,
_Lehrbuch_, II. 2. 824.
[208] Ostwald, _Principles of Inorganic Chemistry_, translated by A.
Findlay, 2nd edit., p. 453 (Macmillan, 1904); Skirrow and Calvert,
_Zeitschr. physikal. Chem._, 1901, 37. 217.
[209] _Vide_ Loewel, _Annales chim. phys._, 1857 [3], 49. 32. Cf.
Loewenherz, _Zeitschr. physikal. Chem._, 1895, 18. 82.
[210] Loewel, _loc. cit._ Gay-Lussac, _Annales chim. phys._, 1819, 11. 296.
For the solubility at higher temperatures, see Tilden and Shenstone, _Phil.
Trans._, 1884, 175. 23. Etard, _Annales chim. phys._, 1894 [7], 2. 548.
[211] Richards, _Zeitschr. physikal. Chem._, 1898, 26. 690; Richards and
Wells, _ibid._, 1903, 43. 465. This temperature is not quite the same as
that of the _quadruple point_ anhydrous salt--hydrated
salt--solution--vapour, because the latter is the temperature at which the
system is under the pressure of its own vapour. Since, however, the
influence of pressure on the solubility is very slight (p. 107), the
position of the two points will not be greatly different. The quadruple
point was found by Cohen (_Zeitschr. physikal. Chem._, 1894, 14. 90) to be
32.6deg and 30.8 mm. of mercury.
[212] Van't Hoff and van Deventer, _Zeitschr. physikal. Chem._, 1887, 1.
185. Cf. Cohen, _ibid._, 1894, 14. 88.
[213] Debray, _Compt. rend._, 1868, 66. 194.
[214] Richards, _Zeitschr. physikal. Chem._, 1898, 26. 690. A number of
other salt hydrates, having transition-points ranging from 20deg to 78deg,
which might be used for the same purpose, have been given by Richards and
Churchill, _ibid._, 1899, 28. 313.
[215] _Zeitschr. physikal. Chem._, 1903, 46. 818.
[216] Van't Hoff, _Lectures on Physical Chemistry_, I. p. 67.
[217] Cohen, _Zeitschr. physikal. Chem._, 1894, 14. 90.
[218] Ziz, _Schweigger's Journal_, 1815, 15. 166. See Ostwald, _Lehrbuch_,
II. 2. 717.
[219] See, for example, the solubility determinations published in
_Wissenschaftliche Abhandl. der physikalisch-technischen Reichsanstalt_,
Vol. III., or in the _Berichte_, for the years 1897-1901.
[220] Meusser, _Ber._, 1901, 34. 2440.
[221] Mylius and von Wrochem, _Ber._, 1900, 33. 3693.
[222] Walker and Fyffe, _Jour. Chem. Soc._, 1903, 83. 180.
[223] _Monatshefte_, 1887, 8. 601.
[224] The equilibria between calcium chloride and water have been most
completely studied by Roozeboom (_Zeitschr. physikal. Chem._, 1889, 4. 31).
[225] Hammerl, _Sitzungsber. Wien. Akad._, 2^{te} Abteil, 1878, 78. 59.
Roozeboom, _Zeitschr. physikal. Chem._, 1889, 4. 31.
[226] Lidbury, _Zeitschr. physikal. Chem._, 1902, 39. 453. The curvature at
the melting point is all the greater the more the compound is dissociated
into its components in the liquid state. If the compound is _completely
undissociated_, even in the vapour phase, the two branches of the curve
will _intersect_, (_e.g._ pyridine and methyl iodide; Aten, _Versl. Konink.
Akad. Wetensch. Amsterdam_, 1905, 13. 462). The smaller the degree of
dissociation, therefore, the sharper will be the bend. (See Stortenbeker,
_Zeitschr. physikal. Chem._, 1892, 10. 194.) From the extent of flattening
of the curve, it is also possible, with some degree of approximation, to
calculate the degree of dissociation of the substance in the fused state.
(See Roozeboom and Aten, _Zeitschr. physikal. Chem._, 1905, 53. 463;
Kremann, _Zeitschr. Elektrochem._, 1906, 12. 259.)
[227] See Roozeboom, _Zeitschr. physikal. Chem._, 1889, 4. 31.
[228] Tammann, _Wied. Annalen_, 1899, 68. 577.
[229] Duhem, _Journ. Physical Chem._, 1898, 2. 31.
[230] Gibbs, _Trans. Conn. Acad._, 3. 155; Saurel, _Journ. Phys. Chem._,
1901, 5. 35.
[231] In the case of the fusion of a compound of two components with
formation of a liquid phase of the same composition, the temperature is a
maximum; in the case of liquid mixtures of constant boiling-point, the
temperature may be a minimum (p. 105).
[232] Roozeboom, _Zeitschr. physikal. Chem._, 1892, 10. 477. The formula of
ferric chloride has been doubled, in order to avoid fractions in the
expression of the water of crystallization.
[233] Roozeboom, _Zeitschr. physikal. Chem._, 1892, 10. 477.
[234] A similar series of hydrates is formed by zinc chloride and water
(Dietz and Mylius, _Zeitschr. anorg. Chem._, 1905, 44. 209).
[235] Meyerhoffer, _Ber._, 1897, 30. 1810.
[236] Walden, _Ber._, 1899, 32. 2863.
[237] _Zeitschr. physikal. Chem._, 1903, 42. 432.
[238] This composition was also confirmed by measurements of the vapour
pressure (cf. p. 90).
[239] Since all substances are no doubt volatile to a certain extent at
some temperature, it is to be understood here that the substances are
appreciably volatile at the temperature of the experiment.
[240] For a general discussion of the partial pressures in a system of two
components, see Bancroft, _Journ. Physical Chem._, 1899, 3. 1.
[241] _Zeitschr. physikal. Chem._, 1889, 3. 11; _Rec. trav. chim.
Pays-Bas_, 1888, 7. 152.
[242] The composition of a solution is represented symbolically by placing
a double wavy line between the symbols of the components, and indicating
the number of atoms present in the ordinary manner: thus, I [wavy] Cl_{_x_}
represents a solution containing _x_ atoms of chlorine to one atom of
iodine (Roozeboom, _Zeitschr. physikal. Chem._, 1888, 2. 450).
[243] Since iodine monochloride in the liquid state is only very slightly
dissociated, the bend at C is very sharp (see p. 147, footnote). See also
the investigation of the system pyridine and methyl iodide (Aten, _Versl.
Konink. Akad. Wetensch. Amsterdam_, 1905, 13. 462).
[244] This upper branch of the curve is not shown in the figure, as the
ordinate corresponding to 30deg would be very great.
[245] Stortenbeker, _Zeitschr. physikal. Chem._, 1889, 3. 22.
[246] Ramsay and Young, _Journ. Chem. Soc._, 1886, 49. 458.
[247] Van't Hoff, _Lectures on Physical Chemistry_, I. p. 77 (Arnold).
[248] This is different from what we found in the case of non-volatile
solutes (p. 126). In the present case, the _partial pressure_ of the iodine
in the vapour will be lowered by addition of chlorine, but the _total
pressure_ is increased.
[249] The diminution of volume is supposed to be carried out at constant
temperature. The pressure and the composition of the phases must,
therefore, remain unchanged, and only the relative amounts of these can
undergo alteration.
[250] At point _b_ the ratio of chlorine to iodine in the solution is less
than in the monochloride, so that by the separation of this the excess of
chlorine yielded by the condensation of the vapour is removed.
[251] Roozeboom, _Rec. trav. chim. Pays-Bas_, 1884, 3. 29; 1885, 4. 65;
_Zeitschr. physikal. Chem._, 1888, 2. 450.
[252] Two curves "enclose" a field when they form with one another an angle
less than two right angles.
[253] Roozeboom, _Zeitschr. physikal. Chem._, _loc. cit._
[254] Van't Hoff, _Zeitschr. physikal. Chem._, 1890, 5. 323.
[255] Bancroft has proposed to restrict the term "occlusion" to the
formation of solid solutions, and to apply "adsorption" only to effects
which are primarily due to surface tension. Such a distinction, however,
would probably be very difficult to carry through, for although adsorption
may, in large measure, be due to surface tension, the behaviour of adsorbed
substances is similar to that of substances existing in solid solutions.
[256] Tammann, _Wied. Annalen_, 1897, 63. 16; _Zeitschr. physikal. Chem._,
1898, 27. 323.
[257] See, for example, Chappuis, _Wied. Annalen_, 1881, 12. 161; Joulin,
_Annal. chim. phys._, 1881, [5], 22. 398; Kayser, _Wied. Annalen_, 1881,
12. 526.
[258] Hoitsema, _Zeitschr. physikal. Chem._, 1895, 17. 1.
[259] _Annales chim. phys._, 1874, [5], 2. 279.
[260] Hoitsema, _Zeitschr. physikal. Chem._, 1895, 17. 1; Dewar, _Phil.
Mag._, 1874, [4], 47, 324, 342; Mond, Ramsay and Shields, _Proc. Royal
Soc._, 1897, 62. 290.
[261] _Loc. cit._
[262] It is noteworthy that the form of curve obtained for hydrogen and
palladium bears a striking resemblance to that for the dehydration of
colloids containing absorbed water, _e.g._ silicic acid (_vide_ van
Bemmelen, _Zeitschr. anorg. Chem._, 1897-1900. Cf. Zacharias, _Zeitschr.
physikal. Chem._, 1902, 39. 480).
[263] _Zeitschr. physikal. Chem._, 1890, 5. 322.
[264] Kuester, _Zeitschr. physikal. Chem._, 1895, 17. 367. Bodlaender,
_Neues Jahrbuch f. Mineralogie_, 1898-99, Beilage Band, 12. 92.
[265] Bruni and Padoa, _Atti Accad. Lincei_, 1902 [5], 11. 1; 565.
[266] Roozeboom, _Zeitschr. physikal. Chem._, 1899, 30. 385; Bruni, _Rend.
Accad. Lincei_, 1898, 2. 138, 347. For a general account of "solid
solutions" the reader is referred to Bruni, "_Ueber feste Loesungen_"
(Ahrens'sche Sammlung), and to Bodlaender, _loc. cit._ For the formation
and transformation of liquid mixed crystals, see A. C. de Kock, _Zeitschr.
physikal. Chem._, 1904, 48. 129.
[267] In discussing the various systems which may be obtained here,
Roozeboom (_loc. cit._) made use of the variation of the thermodynamic
potential (p. 29) with the concentration. In spite of the advantages which
such a treatment affords, the temperature-concentration diagram has been
adopted as being more readily understood and as more suitable for an
elementary discussion of the subject.
[268] These curves are also called the "liquidus" and the "solidus" curve
respectively.
[269] Kuester, _Zeitschr. physikal. Chem._, 1895, 17. 360.
[270] Kuester, _ibid._, 1891, 8. 589.
[271] It should be remarked that the behaviour described here will hold
strictly only when the solid mixed crystals undergo change sufficiently
rapidly to be always in equilibrium with the liquid. This, however, is not
always the case (see Reinders, _Zeitschr. physikal. Chem._, 1900, 32. 494;
van Wyk, _Zeitschr. anorg. Chem._, 1905, 48. 25), and complete
solidification will not in this case take place at the temperature
corresponding with the line _dc_ in Fig. 50, but only at a lower
temperature.
[272] Adriani, _Zeitschr. physikal. Chem._, 1900, 33. 469.
[273] Reinders, _Zeitschr. physikal. Chem._, 1900, 32. 494.
[274] Hissink, _Zeitschr. physikal. Chem._, 1900, 32. 542.
[275] Van Eyk, _Zeitschr. physikal. Chem._, 1899, 30. 430.
[276] Cady, _Journ. Physical. Chem._, 1899, 3. 127.
[277] See Roberts-Austen and Stansfield, _Rapports du congres international
de physique_, 1900, I. 363.
[278] Heycock and Neville, _Proc. Roy. Soc._, 1903, 71. 409. For the
partial liquefaction of mixed crystals on cooling, see also A. C. de Kock
(_Zeitschr. physikal. Chem._, 1904, 48. 129).
[279] Armstrong, _Watt's Dictionary of Chemistry_ (Morley and Muir), III.,
p. 88. See also Lowry, _Jour. Chem. Soc._, 1899, 75. 211.
[280] See Bancroft, _Journ. Physical Chem._, 1898, 2. 143; Roozeboom,
_Zeitschr. physikal. Chem._, 1899, 28. 288.
[281] Hylotropic substances are such as can undergo transformation into
other substances of the same composition (Ostwald, _Lehrbuch_, II. 2. 298).
[282] Also called Equilibrium Point (Lowry).
[283] For a discussion of these systems, see Roozeboom, _Zeitschr.
physikal. Chem._, _loc. cit_.
[284] See Bancroft, _loc. cit._, p. 147; Wegscheider, _Sitzungsber. Wiener
Akad._, 1902, 110. 908.
[285] Reference may be made here to the term "stability limit," introduced
by Knorr (_Annalen_, 1896, 293. 88) to indicate that temperature above
which liquefaction and isomeric change takes place. As employed by Knorr
and others, the term does not appear to have a very precise meaning, since
it is used to denote, not the temperature at which these changes can occur,
but the temperature at which the change is rapid (vide _Annalen_, 1896,
293. 91; 1899, 306. 334); and the introduction of an indefinite velocity of
change renders the temperature of the stability limit also somewhat
indefinite. The definiteness of the term is also not a little diminished by
the fact that the "limit" can be altered by means of catalytic agents.
Since, as we have seen, the stable modification can always undergo isomeric
change and liquefy at temperatures above the natural freezing point, but
not below that point; and, further, the less stable modification can
undergo isomeric transformation and liquefy at temperatures above the
eutectic point, but will not liquefy at temperatures below that; it seems
to the author that it would be more precise to identify these two
points--the natural freezing point and the eutectic point--which are not
altered by catalytic agents, with the "stability limits" of the stable and
unstable modification respectively. A perfectly definite meaning would
thereby be given to the term. In the case of those substances which do not
undergo appreciable isomeric change at the temperature of the melting
point, the stability limits would be the points G and H, Fig. 60.
[286] Cameron, _Journ. Physical Chem._, 1898, 2. 409.
[287] Carveth, _Journ. Phys. Chem._, 1898, 2. 159. See also Dutoit and
Fath, _Journ. chim. phys_., 1903, 1. 358; Findlay, _Trans. Chem. Soc._,
1904, 85. 403.
[288] Hollmann, _Zeitschr. physikal. Chem._, 1903, 43. 129.
[289] For other examples of the application of the Phase Rule to isomeric
substances, see _Journ. Physical Chem._, vols. 2. _et seq._; Findlay,
_Trans. Chem. Soc._, 1904, 85. 403.
[290] See Roozeboom, _Zeitschr. physikal. Chem._, 1899, 30. 410.
[291] See also Saposchnikoff, _Zeitschr. physikal. Chem._, 49. 688;
Kremann, _Monatshefte_, 1904, 25. 1215, 1271, 1311.
[292] J. C. Philip, _Journ. Chem. Soc._, 1903, 83. 821.
[293] _Cf._ also Paterno and Ampolla, _Gazzetta chim. ital._, 1897, 27.
481.
[294] Philip, _loc. cit._, p. 826.
[295] Philip, _loc. cit._, p. 829. Compare curves for iodine monochloride,
Fig. 42, p. 162.
[296] Kuriloff, _Zeitschr. physikal. Chem._, 1897, 23. 676.
[297] Ladenburg, _Ber._, 1895, 28. 163; 1991.
[298] Roozeboom, _Zeitschr. physikal. Chem._, 1899, 28. 494; Adriani,
_ibid._, 1900, 33. 453.
[299] Adriani, _Zeitschr. physikal. Chem._, 1900, 33. 453.
[300] A. Findlay and Miss E. Hickmans.
[301] Kipping and Pope, _Journ. Chem. Soc._, 1897, 71. 993.
[302] See Roozeboom, _Zeitschr. physikal. Chem._, 1899, 28. 512; Adriani,
_ibid._, 1900, 33. 473; 1901, 36. 168.
[303] In this connection reference should be made more especially to the
paper by Roberts-Austen and Stansfield, "Sur la constitution des alliages
metalliques," in the _Rapports du congres international de physique_, 1900,
I. 363; J. A. Mathews, _Journ. of the Franklin Inst._, 1902; Gautier,
_Compt. rend._, 1896, 123. 109; Roberts-Austen, "Reports of the Alloys
Research Committee," in _Journ. Inst. Mechan. Engineers_, from 1891 to
1904; and the papers by Heycock and Neville, published in the _Journ. Chem.
Soc._, and the _Trans. Roy. Soc._ since 1897; also Neville, _Reports of the
British Association_, 1900, p. 131. Reference must also be made to the
important metallographic investigations by Tammann and his pupils, and of
Kurnakoff (_Zeitschr. anorgan. Chem._, vol. 40 and onwards), and also to
those of Shepherd, _Journ. Physical Chem._, 8. A bibliography of the alloys
is given in _Zeitschr. anorgan. Chem._, 1903, 35. 249.
[304] Kurnakoff and Puschin, _Zeitschr. anorgan. Chem._, 1902, 30. 104.
[305] Gautier, _Bull. Soc. d'Encouragement_, 1896 [5], 1. 1312.
[306] Heycock and Neville, _Phil. Trans._, 1900, 194. 201.
[307] Gautier, _loc. cit._ See also Roberts-Austen and Rose, _Proc. Roy.
Soc._, 1903, 71. 161.
[308] Heycock and Neville, _Journ. Chem. Soc._, 1897, 71. 414.
[309] See Roberts-Austen, _Introduction to Metallurgy_, 5th edit., p. 102;
Bakhuis Roozeboom, _Journ. Iron and Steel Inst._, 1900, II. 311; _Zeitschr.
physikal. Chem._, 1900, 34. 437; von Jueptner, _Siderology_, p. 223
(translation by C. Salter); van't Hoff, _Zinn, Gips, und Stahl_, p. 24, or
_Acht Vortraege ueber physikalische Chemie_, p. 37. Further, Roozeboom,
_Zeitschr. Elektrochem._, 1904, 10. 489; E. Heyn, _ibid._, p. 491;
Carpenter and Keeling, _Journ. Iron and Steel Inst._, 1904, 65. 224.
[310] The melting point of pure iron is given by Carpenter and Keeling
(_Journ. Iron and Steel Inst._, 1904, 65. 224) as 1505deg.
[311] _Zeitschr. fuer Elektrochem._, 1904, 10. 491.
[312] See also Hiorns, _Journ. Soc. Chem. Ind._, 1906, 25. 50.
[313] Bancroft, _Jour. Physical Chem._, 1902, 6. 178; Bell and Taber,
_ibid._, 1906, 10. 120.
[314] The method to be followed when the third component enters into the
solid phase will be explained later.
[315] Tammann, _Zeitschr. anorg. Chem._, 1903, 37. 303; 1905, 45. 24.
Reference may be made here to the registering pyrometer of Kurnakoff,
_Zeitschr. anorg. Chem._, 1904, 42. 184.
[316] In this connection, see Doelter, _Physikalisch-chemisch Mineralogie_
(Barth, 1901); Meyerhoffer, _Zeitschr. f. Kristallographie_, 1902, 36. 593;
Guthrie, _Phil. Mag._, 1884 [5], 17. 479; Le Chatelier, _Compt. rend._,
1900, 130. 85; and especially E. Baur, _Zeitschr. physikal. Chem._, 1903,
42. 567; J. H. L. Vogt, _Zeitschr. Elektrochem._, 1903, 9. 852, and _Die
Silikatschmelzloesungen_, Parts I. and II. (Christiania, 1903, 1904). See
also N. V. Kultascheff, _Zeitschr. anorg. Chem._, 1903, 35. 187.
[317] G. G. Stokes, _Proc. Roy. Soc._, 1891, 49. 174; Gibbs, _Trans. Conn.
Acad._, 1876, 3. 176; Roozeboom, _Zeitschr. physikal. Chem._, 1894, 15.
147.
[318] This figure has been taken from Ostwald's _Lehrbuch_, II. 2. 984.
[319] Roozeboom, _Zeitschr. physikal. Chem._, 1893, 12. 369.
[320] C. R. A. Wright, _Proc. Roy. Soc._, 1891, 49. 174; 1892, 50. 375.
[321] The distribution coefficient will not remain constant because, apart
from other reasons, the mutual solubility of chloroform and water is
altered by the addition of the acid.
[322] Bancroft, _Physical Review_, 1895, 3. 21; Schreinemakers, _Zeitschr.
physikal. Chem._, 1897, 23. 652, and subsequent volumes.
[323] C. R. A. Wright, _Proc. Roy. Soc._, 1889-1893.
[324] C. R. A. Wright, _Proc. Roy. Soc._, 1892, 50. 390.
[325] Bodlaender, _Berg- und Huettenmaenn. Ztg._, 1897, 56. 331.
[326] C. R. A. Wright, _Proc. Roy. Soc._, _loc. cit._
[327] Schreinemakers, _Zeitschr. physikal. Chem._, 1900, 33. 78.
[328] Schreinemakers, _Zeitschr. physikal. Chem._, 1898, 27. 95.
[329] Schreinemakers, _Zeitschr. physikal. Chem._, 1899, 29. 577.
[330] Schreinemakers, _Zeitschr. physikal. Chem._, 1898, 25. 543.
[331] Charpy, _Compt. rend._, 1898, 126. 1569. Compare the curves for the
system KNO_{3}--NaNO_{3}--LiNO_{3} (H. R. Carveth, _Journ. Physical Chem._,
1898, 2. 209). Also alloys of Pb--Sn--Bi (E. S. Shepherd, _Journ. Physical
Chem._, 1902, 6. 527).
[332] It should be remembered that in the triangular diagram a _line_
parallel to one of the sides indicates, at a given temperature, a constant
amount of the component represented by the opposite corner of the triangle;
and, hence, points in a _plane_, parallel to one face of a right prism,
will indicate for different temperatures, variation in the amounts of two
components, but constancy in the amount of the third.
[333] _Gazzetta chim. ital._, 1898, 28. II. 520.
[334] Bruni, _Gazzetta chim. ital._, 1898, 28. II. 508; 1900, 30. I. 35.
[335] _Zeitschr. physikal. Chem._, 1900, 36. 168.
[336] For a discussion of these systems, see van't Hoff, _Bildung und
Spaltung von Doppelsalzen_ (Leipzig, 1897).
[337] Van Leeuwen, _Zeitschr. physikal. Chem._, 1897, 23. 35.
[338] Meyerhoffer, _Zeitschr. physikal. Chem._, 1889, 3. 336; 1890, 5. 97.
[339] Reicher, _Zeitschr. physikal. Chem._, 1887, 1. 220.
[340] For other examples of the formation and decomposition of double salts
at a transition point, the reader is referred to the work by van't Hoff,
already cited, on the _Bildung und Spaltung von Doppelsalzen_; or to
Bancroft, _Phase Rule_, p. 180.
[341] Bancroft, _Phase Rule_, p. 183.
[342] Roozeboom, _Zeitschr. physikal. Chem._, 1888, 2. 514.
[343] The influence of pressure on the transition point in the case of
tachydrite has been determined by van't Hoff, Kenrick, and Dawson
(_Zeitschr. physikal. Chem._, 1901, 39. 27, 34; van't Hoff, _Zur Bildung
der ozeanischen Salzablagerungen_, I. p. 66--Brunswick, 1905). This salt is
formed from magnesium chloride and calcium chloride at 22deg, in accordance
with the equation--
2MgCl_{2}.6H_{2}O + CaCl_{2}.6H_{2}O = Mg_{2}CaCl_{6}.12H_{2}O + 6H_{2}O
Increase of pressure raises the transition point, because the formation of
tachydrite is accompanied by increase of volume; the elevation being
0.016deg for an increase of pressure of 1 atm. The number calculated from
the theoretical formula (p. 57) is 0.013deg for 1 atm.
If one calculates the influence of the pressure of sea-water on the
temperature of formation of tachydrite (which is of interest on account of
the natural occurrence of this salt), it is found that a depth of water of
1500 metres, exerting a pressure of 180 atm., would alter the temperature
of formation of tachydrite by only 3deg. The effect is, therefore,
comparatively unimportant.
[344] Roozeboom, _Zeitschr. physical. Chem._, 1887, 1. 227.
[345] _Zeitschr. physical. Chem._, 1887, 1. 227.
[346] Van't Hoff and Mueller, _Ber._, 1898, 31. 2206.
[347] Van't Hoff and van Deventer, _Zeitschr. physikal. Chem._, 1887, 1.
165.
[348] For a full discussion of the solubility relations of sodium ammonium
racemate, see van't Hoff, _Bildung und Spaltung von Doppelsalzen_, p. 81.
[349] _Annales chim. phys._, 1848 [3], 24. 442.
[350] See Van't Hoff and van Deventer, _Zeitschr. phys. Chem._, 1887, 1.
165.
[351] Meyerhoffer, _Zeitschr. physikal. Chem._, 1890, 5. 121.
[352] Roozeboom, _Zeitschr. physikal. Chem._, 1888, 2. 518.
[353] Meyerhoffer, _Zeitschr. physikal. Chem._, 1890, 5. 109. On the
importance of the transition interval in the case of optically active
substances, see Meyerhoffer, _Ber._, 1904, 37. 2604.
[354] In connection with this chapter, see, more especially, van't Hoff,
_Bildung und Spaltung von Doppelsalzen_, p. 3, _ff._; Roozeboom, _Zeitschr.
physikal Chem._, 1892, 10. 158; Bancroft, _Phase Rule_, p. 201; 209.
[355] The same restriction must be made here as was imposed in the
preceding chapter, namely, that the two salts in solution give a common
ion.
[356] For example, addition of ammonium chloride to solutions of ferric
chloride (Roozeboom, _Zeitschr. physikal. Chem._, 1892, 10. 149).
[357] It must, of course, be understood that the temperature is on that
side of the transition point on which the double salt is stable.
[358] Excess of the double salt must be taken, because otherwise an
unsaturated solution might be formed, and this would, of course, not
deposit any salt.
[359] Meyerhoffer, _Ber._, 1904, 37. 2605.
[360] Meyerhoffer, _Ber._, 1897, 30. 1809.
[361] Meyerhoffer, _Ber._, 1904, 37. 2604.
[362] Bancroft, _Phase Rule_, p. 203; Roozeboom, _Zeitschr. physikal.
Chem._, 1891, 8. 504, 531; Stortenbeker, _ibid._, 1895, 17. 643; 1897, 22.
60; 1900, 34. 108.
[363] Roozeboom, _Zeitschr. phys. Chem._, 1899, 28. 494; _Ber._, 1899, 32.
537.
[364] As, for instance, strychnine racemate, a compound of racemic acid
with the _optically active_ strychnine. This would be resolved into
strychnine _d_-tartrate and strychnine _l_-tartrate, which are not
enantiomorphous forms.
[365] Van't Hoff and Meyerhoffer, _Zeitschr. physikal Chem._, 1898, 27. 75;
1899, 30. 86. Fig. 113 is taken from the latter paper.
[366] Solid models constructed of plaster of Paris can be obtained from Max
Kaehler and Martini, Berlin.
[367] Instead of the present method of obtaining potassium chloride by
decomposing carnallite with water, advantage might be taken of the fact
that carnallite when heated to 168deg undergoes decomposition with
separation of three-fourths of the potassium chloride (van't Hoff, _Acht
Vortraege ueber physikalische Chemie_, 1902, p. 32).
[368] Roozeboom and Schreinemakers, _Zeitschr. physikal. Chem._, 1894, 15.
588.
[369] These curves represent only portions of the isotherms, since the
systems in which a ternary solution is in equilibrium with solid hydrogen
chloride or a hydrate, have not been investigated.
[370] The numbers printed beside the points on the curves refer to the
number of the experiment in the original paper.
[371] Lash, Miller and Kenrick, _Journ. Physical. Chem._, 1903, 7. 259;
Allan, _Amer. Chem. Journ._, 1901, 25. 307.
[372] Allan, _Amer. Chem. Journ._, 1901, 25. 307.
[373] Hoitsema, _Zeitschr. physikal. Chem._, 1895, 17. 651; Allan, _loc.
cit._
[374] Rutten, _Zeitschr. anorgan. Chem._, 1902, 30. 342. Compare the system
BeO--SO_{3}--H_{2}O; Parsons, _Zeitschr. anorgan. Chem._, 1904, 42. 250.
[375] _Zeitschr. anorgan. Chem._, 1904, 40. 146.
[376] Schreinemakers, _Zeitschr. physikal. Chem._, 1893, 11. 76; Bancroft,
_Journ. Physical Chem._, 1902, 6. 179.
[377] _Zeitschr. anorgan. Chem._, 1904, 40. 148.
[378] _Zeitschr. physikal. Chem._, 1903, 43. 354.
[379] These equilibria were obtained by Boudouard, _Annales chim. phys._,
1901 [7], 24. 5. See also Hahn, _Zeitschr. physikal. Chem._, 1903, 42.
705; 44. 513.
[380] G. Preuner, _Zeitschr. physikal. Chem._, 1903, 47. 385.
[381] See Hahn, _Zeitschr. physikal. Chem._, 1903, 42. 705; 44. 513;
Boudouard, _Bull. Soc. chim._, [3], 25. 484; Bodlaender, _Zeitschr. f.
Elektrochem._, 1902, 8. 833; R. Schenck and Zimmermann, _Ber._, 1903, 36.
1231, 3663; Schenck and Heller, _ibid._, 1905, 38. 2132; _Zeitschr. f.
Elektrochem._, 1903, 9. 691; Haber, _Thermodynamik technischer
Gasreaktionen_, p. 293 (Munich, 1903).
[382] A very useful summary of the investigations carried out by van't Hoff
and his pupils on the formation of the Stassfurt salt-beds is given by E.
F. Armstrong, in the _Reports of the British Association for 1901_, p. 262.
See also van't Hoff, _Zur Bildung der ozeanischen Salzablagerungen_
(Brunswick, 1905).
[383] See especially Meyerhoffer, _Silzungsber. Wien. Akad._, 1895, 104.
II. _b_, 840; Meyerhoffer and Saunders, _Zeitschr. physikal. Chem._, 1899,
28. 453; 31. 370. The investigation of the equilibria between reciprocal
salt-pairs alone (three-component systems) is of great importance for the
artificial preparations of minerals, as also in analytical chemistry for
the proper understanding of the methods of conversion of insoluble systems
into soluble by fusion (see Meyerhoffer, _Zeitschr. physikal. Chem._, 1901,
38. 307).
[384] See Meyerhoffer, _Zeitschr. physikal. Chem._, 1899, 28. 459.
[385] Compare the reciprocal salt-pair NaCl--NH_{4}HCO_{3} (p. 321). In
this case the upper limit of the transition interval was found by
extrapolation of the solubility curve for NaHCO_{3} + NH_{4}Cl +
NH_{4}HCO_{3} and NaHCO_{3} + NH_{4}Cl + NaCl to be 32deg (Fedotieff,
_Zeitschr. phys. Chem._, 1904, 49. 179).
[386] Loewenherz, _Zeitschr. physikal. Chem._, 1894, 13. 464.
[387] Meyerhoffer and Saunders, _Zeitschr. physikal. Chem._, 1899, 28. 479.
[388] As the quantities of the salts are expressed in _equivalent_
gram-molecules, the molecule of sodium and potassium chloride must be
doubled in order to be equivalent to sodium sulphate and potassium
sulphate.
[389] _Sitz-Ber. der kgl. preuss. Akad. der Wiss._, 1903, p. 359. Van't
Hoff, _Zur Bildung der ozeanischen Salzablagerungen_, I. p. 34 (Brunswick,
1905).
[390] _Zeitschr. fuer Kristallographie_, 1904, 39. 155.
[391] Meyerhoffer and Saunders, _Zeitschr. physikal. Chem._, 1899, 28. 479.
[392] _Zeitschr. physikal. Chem._, 1904, 49. 162.
[393] Another commercial process, in the study of which good service is
done by the Phase Rule, is the caustification of the alkali salts (G.
Bodlaender, _Zeitschr. fuer Elektrochem._, 1905, 11. 186; J. Herold,
_ibid._, 418).
[394] _Zeitschr. physikal. Chem._, 1900, 35. 32.
[395] Mention may also be made here of the equilibria between magnesium
carbonate and potassium carbonate, although these do not form a reciprocal
salt-pair (Auerbach, _Zeitschr. fuer Elektrochem._, 1904, 10. 161).
[396] O. N. Witt and K. Ludwig, _Ber._, 1903, 36. 4384; Meyerhoffer,
_ibid._, 1904, 37. 261, 1116.
[397] _Zeitschr. physikal. Chem._, 1905, 53. 513. Compare also, _ibid._,
1903, 38. 307.
[398] See Schwarz, _Beitraege zur Kenntnis der umkehrbaren Umwandlungen
polymorpher Korper_ (Goettingen, 1892); or, Roozeboom, _Heterogen.
Gleichgewicht_, I. p. 125. Also Barnes and Cooke, _Journ. Physical Chem._,
1902, 6. 172.
[399] Van't Hoff and van Deventer, _Zeitschr. physikal. Chem._, 1887, 1.
173.
[400] Reicher, _Zeitschr. fuer Krystallographie_, 1884, 8. 593.
[401] _Zeitschr. physikal. Chem._, 1895, 17. 153.
[402] _Zeitschr. physikal. Chem._, 1899, 28. 464.
[403] Meyerhoffer and Saunders, _ibid._, p. 466.
[404] See Van Eyk, _Zeitschr. physikal. Chem._, 1899, 30. 446.
[405] See in this connection the volume in this series on
_Electro-chemistry_, by Dr. R. A. Lehfeldt.
[406] Barnes and Cooke, _Journ. Physical Chem._, 1902, 6. 172.
[407] For a description and explanation of these, the reader should consult
the volume in this series by Dr. Lehfeldt on _Electro-chemistry_; and van't
Hoff, _Bildung und Spaltung von Doppelsalzen_, p. 48 _ff._
* * * * *
Changes made to the printed original.
Pages 30-31. "Fig. 3, p. 27.": 'p. 25." in original. So also page 33, "Fig.
2, p. 27".
Page 57. "pp. 29 and 35": 'pp. 25 and 38" in original.
Page 65. "p. 57.": 'p. 60" in original (twice).
Page 166. "there is the point C_{1}": C' in original.
Page 225. "C is an eutectic point": 'eutetic' in original.
Page 228. "Although this view put forward by Heyn": 'Athough' in original.
Page 232. "the period of constant temperature for the eutectic point c":
'the eutectic point e' in original.
Page 249. "two liquid layers between 13deg and 31deg": 'betwen' in
original.
Page 257. Tables entries 4 and 7. "naphthol": 'napthol' in original.
Page 287. "from which the model is constructed": 'he model' in original.