SOLUTIONS OF CERTAIN HYDROXIDES—MACGREGOR. 375 
maximum contraction, the solution which exhibits it, or the limit 
of concentration within which contraction occurs. 
AMMONIUM Hyprox1pE,—NH,OH. 
As Ammonium is closely related in the properties of its com- 
pounds to the metals of the alkalies, it may be well to givea 
table similar to the above, for solutions of its hydroxide, though 
' as the densities of these solutions are less than unity it is obvious 
that their expansions must be positive. The table is based on 
experiments by Thomsen. 
: Volume at 18° 
D ty at Vol fel 
z oN ELOH of ( 18° Gem of soln, ey, pie ree Ey 
: 3 rms, cu. t 18 Syssetais : ‘ : 
in solution. 8 a ve (aus cm.) Ceca (cu. cm 
1.9103 0.9954 1.0046 0.93822 +0.0224 
3.7491 0.9914 1.0087 0.9638 +0.0349 
6.0961 0.9865 1.0137 0.94038 +0.0734 
The NH,OH curve of Plate I. shews the results of this table 
graphically. It is much steeper than the others; and, if the 
observations are exact, has a point of contrary flexure. If we 
regard the experiments as not sufficiently exact to establish the 
contrary flexure, the curve must be regarded as practically a 
straight line. 
Barium HyproxipDE,—Ba O, H.,, 
For Barium Hydroxide, Kohlrausch has published two deter- 
minations which serve as the basis of the following table :— 
Volume at 18° 
Density at Vol eal 
SS “18° . peat, of solut’n, Pee aa Expansion 
: : 3 ; t 18 : ; nels 
in solution. Ee xs Be a) chiang (cu, cm.) 
1.33 1.0128 0.9873 0.9880 | —0.0007 
2.67 1.0271 0.9736 0.9746 | —0.0010 
