c.c. 
1903 - 4 .] Thermal Expansion of Solutions of Hydroxides. 287 
It thus appears that for solutions of this hydrate below a 
certain dilution the expansion is negative, and that this negative 
expansion becomes less numerically with rise of temperature, i.e. it 
increases algebraically with the temperature, just as is the case 
when the expansion is positive (see fig. 2). 
The following are curves for sodium hydroxide showing 
expansion on solution plotted against concentration for the various 
temperatures. 
The solution exhibiting the maximum contraction at 15° C. is 
0 & JO i& 
Fig. 1. 
one containing 6 '07 per cent, of the hydroxide, while the corre- 
sponding value deduced by Professor MacGregor is 6 per cent. 
The maximum contraction, as deduced from the above graph, is 
•004:4 c.c., while that given by Professor MacGregor is '0045. The 
crosses on the diagram indicate values taken from Professor 
MacGregor’s table. It is also to be noted that contraction decreases 
with rise of temperature, and that the maximum contraction- 
