DlÜYMIUM. 



29 



SPECIBIC GRAVITIES AKD MOLECULAE VOLUMES OF THE ANA- 

 LOGOUS COMPOUNDS OF DIDYMIUM AND SAMARIUM. 



D i d y m i u ni Samarium 



Sp. gr. M. vol. Sp. gr. M. vol. 



«jOj 7.179 40.2 8.347 41. T 



RCI3+6H2O 2.286 155.9 2.383 153.0 



ROCl 5.751 33.6 7.017 28.7 



RBra + eHoO 2.810 174.4 2.971 167.6 



llC!6Au + 10H.,O 2.663 274.5 2.742 269.5 



RBi-jAu + lOHjO 3.304 302.1 3.390 296.7 



RCl7Pt + 10V2H.jO 2.689 288 2.712 288.5 



R3XO3 + 61120 2.249 193.9 2.375 186.9 



RIOä + 4H20 3.760 112 3.793 113. i 



R„3S04 3.667 156 3.898 150.8 



R.^3S04 + 8H.,0 2.829 253.1 2.930 249.6 



RXH42SO, 3.080 114.3 3.191 112.8 



RNH42SO4 + 4H2O 2.575 164.7 2.675 161.5 



R.j3Se04 4.442 160.5 4.077 178.8 



RK2Se04 3.839 121.7 4. 113 115.5 



RBO3 5.700 35.3 6.048 34.6 



RP.0,4 3.345 155.8 3.487 151.7 



RV,0,4 + 28H.jO 2.494 700 2.524 698.0 



R3CH0., 3.430 80.8 3.733 76.35 



R3C.2H30.^ 2.157 150.1 2.208 148.1 



R3C2H3 0j + 4H.,0 1.882 207.8 1.940 205.7 



R3C3H5O2 1.861 194 1.894 194.8 



R3C3H5 0.,+ 3H,0 1.741 238.4 1.786 237 



R3C2H3,3SO, +'9H.,0 1.863 364.5 1.879 365.6 



From the above list it seems as a general rule that the compounds 

 of didj'minm are lower in density than the compounds of samarium, but, 

 on the other hand, the molecular volume of the didymium-compounds 

 is larger. 



Still there are some exceptions. The density of the anhydrous 

 selenate of didymium has been found higher than that of the samarium- 

 s^alt, an exception which I cannot explain. The molecular volumes of 

 the chloroplatinates, the periodate, the anhydrous propionate and ethyl- 

 sulphate of didymium are slightly less than the volumes of the corre- 

 sponding samariumsalts, which I will ascribe to inexactness in the de- 

 terminations or perhaps impurities. 



