518 On Freezing-point Depressions for Electrolytes. 



thereabout. At their lower ends they turn sharply to the left 

 and cross the 2—3 line, going towards the region of the double- 

 molecule curves or of the 2—2 curve. The turns are too sharp 

 and the 4-6 and 6-9 lines too near to make their transforma- 

 tion probable into double or triple molecule curves with un- 

 changed mode of ionization. The diagram suggests rather their 

 transformation into 4-5, 4, or 2 or 2-2 curves. If this be 

 accepted, it means that at extreme dilution these sulphates 

 exist in solution in single molecules dissociating into three 

 ions, that partial dissociation into two ions or doubling of 

 molecules sets in apparently at an early stage, but increases 

 more slowly than in the case of H 2 S0 4 until the dilution has 

 been considerably diminished, when it undergoes rapid 

 increase. A close determination of the depression-constant 

 cannot be made ; but even if the curves have to be either 

 raised or lowered a little and if, LoonhVs tendency being left- 

 ward, their upper ends have to be shifted somewhat to the 

 right, they will be consistent with its being about 1'85. 



The Na 3 C0 3 curves are too discordant to form a basis for 

 discussion. But either Loomis's curve or a mean curve, or 

 even Jones's curve itself is quite consistent with a depression 

 constant of about 1'85 ; and both curves indicate the occur- 

 rence of rapid association or of rapid change of mode of 

 ionization after considerable diminution of dilution. The fact 

 that Loomis's curves tend towards the left, suggests that the 

 actual curve after starting at the 2-3 intersection may bend 

 considerably to the right before association or change of mode 

 of ionization has advanced sufficiently to change the direction 

 of its curvature. 



An electrolyte such as MgS0 4 , according as it may exist in 

 solution in single, double, or triple molecules, and according 

 to their mode of ionization, may have a 2—2, 4-4 or 2/ or 

 6-6, 4, 3 or 2 curve. Jones's curve lies to the right of the 

 2-2 (1'85) line, bending towards it, and may quite readily be 

 a 2-2 (1'85) curve changing to a 4-4 or 4—2 curve. Loomis's 

 lies between the 2-2 and 4-4 lines. A mean curve would, at 

 a concentration "02, have already crossed the 2-2 line. The 

 data, such as they are, are consistent with the depression-con- 

 stant having a value of about 1'85, and would indicate single 

 molecules in dilute solutions, doubling of molecules at a very 

 early stage, and a steady increase in association throughout. 



According as H 3 P0 4 , if it exist in solution in single mole- 

 cules, may dissociate into 4, 3, or 2 ions, will it have a 3-4,, 

 3-3, or 3-2 curve. If it have double molecules, its curve 

 may be a 6-8, 6-7, &c. to 6-2 curve, according to the mode 

 of ionization. Jones's curve, far to the left of the 3-4 and 3-3 



