516 Prof. J. G. MacGregor on a Diagram of 



The HN0 3 curve (see inset) is a mean curve based on 

 Loorais's and Jones's. Both are beyond the bounds of the 

 inset, the former to the left and the latter to the right. 

 Neither this curve nor that of KN0 3 is sufficiently trust- 

 worthy to warrant any close inspection ; but both are clearly 

 consistent with the 1*85 value of the depression-constant. 

 If the leftward bending of the KN0 3 curve in its lower part 

 were actual, as well as the position of the curve, the formation 

 of triple molecules might be indicated. But being a Loomis 

 curve, it is open to the suspicion of being as a whole too far 

 to the left, and it is plotted with doubtful coefficients. 



The KOH curves, Loomis's on the main diagram and 

 Jones's on the inset, are useful only to illustrate the difficulty 

 of making concordant observations by different methods. 

 As usual, Loomis's is to the left and Jones's to the right. 



Electrolytes such as BaCl 2 , H 2 R0 4 , Na 2 00 3 have 2 equi- 

 valents in the single molecule which may dissociate into 3 or 

 into 2 ions. If there is no association, they will therefore 

 have 2-3 or 2-2 curves according to the mode of ionization. 

 If there is complete doubling of molecules, the curves will be 

 4-6 or 4-4 curves, provided the doubling does not involve change 

 in mode of ionization. Otherwise they might be 4-5, 4-3, or 

 4-2 curves. If the molecules are associated in threes, the 

 curves will be 6-9 or 6—6 curves, with the above proviso. 



Both Loomis's and Jones's curves for BaCl 2 are shown on 

 the diagram, plotted with Whetham's coefficients (rough 

 extrapolated values, however, in the case of the former). 

 Ponsot's curve agrees very closely with Loomis's. Bearing 

 in mind the rightward and leftward tendencies of Jones's and 

 Loomis's curves respectively, we may conclude from the 

 curves of the diagram that the actual curve runs down to the 

 right of the 2—2 line, bending away from it to the right, and 

 that it would intersect the a. = 1 line at a point between the 

 2-3 (1*85) and the 2-3 (1'87) intersections, probably nearer 

 the former than the latter. The curve is thus, so far as we 

 can judge, a normal 2-3 (1*85 + '0l) curve, running however 

 very close to the 2-3 line. The diagram therefore indicates 

 that BaCl 2 exists in solution in single molecules, dissociating 

 into three ions, at least for the most part, and that it has a 

 depression-constant nearer 1*85 than 1"87. 



The ELjSCXt (J-W) curve for high dilutions being a Jones 

 curve, is probably too far to the right, and, being plotted 

 with "Whetham's coefficients, is probably too high. Wilder- 

 mann's curve for high dilutions runs parallel to it, con- 

 siderably to the left. The JLB-B curve for lower dilutions 

 is very nearly coincident with Barnes's curve, and in its lower 



