78 



WORK OF J. N. PEARCE. 



A glance at column a (table 59) shows us that, in spite of the tendency of this salt 

 to hydrolyze, the dissociation decreases very rapidly with increase in concentration. 

 This is just what might be predicted. Its atomic volume is very small and the 

 hydrating power of its cation very large; therefore it should have a very small 

 migration velocity. 



Table 59. Aluminium Chloride Data for Freezing-point and Conductivity Measurements, 



Specific Gravity, and Hydrates. 



Freezing-point. 



m 



0.01 I 



0.025J 



0.050 



0.075 



0.10 



0.25 



0.50 



0.75 



1.00 



1.50 



2.0 



(I 

 (I 

 



1 

 :! 



7 



11 



25 



48 



712 



1623 



3053 



4511 



4511 



6604 



9446 



1339 



795 



5 1 



5 1 



A/m 



a 



7.1200' 

 6.4940, 

 6.1060' 

 6.0153 

 5.0850 

 6.641 

 7.889 

 9.511 

 11.795 

 17.000 

 24.25 



3 



8 

 3 

 3 

 :s 

 3 

 4 

 5 

 6. 

 9. 

 13. 



8279 

 4193 

 2827 

 2340 

 2704 

 5708 

 2415 

 1137 

 3410 

 1398 

 037 



94.20 

 80.04 

 76.09 

 74.46 



Hydrates. 



m 



0.01 



0.025 



0.050 



0.075 



0.10 



0.25 



0.50 



1.00 



1.5 



2.0 



a 



A/'m 



L' 



M 



92.04 

 83.08 

 76.72 

 74.50 

 71.80 

 62. 8S 

 44.12 



36.42 

 24.48 

 14.98 



6.9958 



6.4958 



6.1409 



6.0111 



5.8664 



5.368 



4.321 



7.1200 



6.4940 



6.1060 



6.1526 



6.1560 



6.641 



9.511 



7.1180 



6.4907 



6.1012 



6.1447 



6.1452 



6.613 



9.362 



3.892 11.795 11.523 

 3.225 17.000 ?16.369 

 2.695 24.25 |22 . 963 



H 



2.52 25.2 



10.54 42.16 



9.91 39.88 



36.78 

 44.60 

 49.03 



36.78 

 29.33 

 24.51 



Conductivity. m^0 = 170. 2 



Me 



100 

 40 

 20 



13.334 

 10 



4 



2 



1.333 



1 



1.6667 



0.5 



156.48 



141.24 



130.44 



126.66 



122.07 



106.90 



88.60 



75.02 



61.93 



41.62 



25.47 



92.04 

 83.08 

 76.72 

 74.50 

 71.80 

 62.88 

 52.11 

 44.12 

 36.42 

 24.48 

 14.98 



Specific gravity. 



m 



Sp. gr. 



0.01 



0.025 



0.05 



0.075 



0.1 



0.25 



0.55 



1.00 

 1.5 



2.00 



1.00104 

 1.00282 

 1.00588 

 1.00870 

 1.01158 

 1.02911 

 1.05706 

 1.08431 

 1.11054 

 1 . 16308 

 1.21378 



W, 



sol 



II 



salt 



Wh.o 



1001.04 

 1002.82 

 1005.88 

 1008.70 

 1011.58 

 1029.11 

 1057.06 

 1084.31 

 1110.54 

 1163.08 

 1213.78 



1.3345 

 3.3625 

 6.6725 

 10.0087 

 13.345 

 33.36 

 66.725 

 100.087 

 133.45 

 200.175 

 266.90 



999.71 

 999.49 

 999.21 

 998.70 

 998.24 

 995.75 

 990.33 

 988.22 

 977.09 

 962.90 

 946.88 



Correction, 

 per cent. 



0.029 



0.051 



0.079 



0.130 



0.176 



0.425 



0.966 



1.57 



2.29 



3.70 



5.31 



'These freezing-points were determined by an alcohol thermometer, and freezing-mixtures of solid carbon dioxide and ether. 

 J Amer. Chem. Journ.. 31, 333 (1904). 



SODIUM BROMIDE. 



Dilute portions of the mother-solution were standardized volumetrically by Vol- 

 hard's method. This salt differs from those preceding in that it is a binary electrolyte 

 and crystallizes with two molecules of water. A study of table 60 brings out the 

 same general results. The observed molecular lowering passes through a minimum 

 between 0.5 and 0.75 normal. The minimum in the total amount of combined water 

 occurs at 0.10 normal. From the amounts of water which combine with one gram- 

 molecule of the salt, it will be seen that the sodium cation has nearly the same hydrat- 

 ing power in dilute solutions as do the cations of the calcium and copper groups. 



The atomic volume of sodium is slightly more than half that of potassium. Its 

 hydrating power, however, for the more dilute solutions is much greater. If, then, 

 the amount of hydration of the sodium ion is more than sufficient to compensate for 



