THE FLUIDITY OF SOLUTIONS 181

remained undiscovered. That positive curvature is general even
when it is quite unsuspected in dilute solutions is proved by
all of the data available, as may be seen by inspection of Figs.
67, 68, 69 and 70. The negative curvature is in each case most

Z25

200,

175 P

100

75

50

25

^*

SN

X

10 ZO 30 40 50 60 70 50 90 100
Fluidity of Solutions of Urea

• FIG. 68.

200

100}

\
\

"0 10 TLO 30 40 50 60 TO 80 90 JOO
Fluidify of Solutions of Silver Nitrate

FIG. 69.

pronounced at the lowest temperatures and in solutions contain-
ing not over 20 per cent of the salt by volume. The .negative
curvature disappears in concentrated solutions and at high
temperatures. If the negative curvature is strongly marked,
as with ammonium nitrate or potassium chloridej the positive
curvature is unimportant, but when the negative curvature