1880.J On the Rare Earths and their Sulphates. 49 



Hydrated Sulphates. 



Compounds. 



Formula. 



Molecular 

 weight. 



Specific 

 weight. 



Specific 

 heat. 



Molecular 

 heat. 



Molecular 

 volume. 



Lanthanum sulphate .... 

 Cerium sulphate 



Ytterbium sulphatef 



Be 2 3S0 4 .12H 2 

 Y o 3S0 4 .8H o 0... 

 La„3S0 4 .9H 2 0. 

 Ce 2 ~3S0 4 .5H 2 0. 

 Di 2 3S0 4 .8H„0. 

 Er 2 3S0 4 .8H;,0. 

 Yb 2 3S0 4 .8H" 2 0. 



531 3 

 611-0 

 728-0 

 657 

 725 -0 

 764-0 

 778-0 



1- 713 



2- 540 



2- 853 



3- 220 



2- 878 



3- 180 

 3-286 



0-2257 

 -2083 

 0-1999 

 0*1948 

 0-1808 

 0-1788 



137 -91 

 151-64 

 131 -33 

 141-23 



138- 13 



139- 11 



310-17 



240 -55 

 255-17 

 204 -04 

 251-91 

 240 -25 

 236-79 



On subtracting the values obtained for the anhydrous salts from 

 the same numbers of the hydrated sulphates, we obtain a remainder 

 expressing the molecular heat and volume of the water in combination. 

 Thus the following values are obtained : — 



Compounds. 



Water in 

 combination. 



Molecular 

 heat. 



Molecular 

 volume. 



Ytterbium sulphate. . . 



Didymium sulphate . . 

 Lanthanum sulphate . 



8H..0 

 8H 2 



8H 2 



8H 2 



9HoO 



5EUO 



9-15 

 921 

 954 

 9 03 

 9-42 

 13-02 



870 

 8-96 

 7-72 

 1204 



10- 88 



11- 82 



The molecular heat and volume of free water being =18, it will be 

 seen that by entering into combination with the sulphates of the rare 

 earth-metals, its heat and volume are reduced in an extraordinary 

 degree. In fact, the molecular heat and volume of water in these 

 salts descends to a minimum value hitherto unknown. 



Comparing the values given above, we readily find that in those 

 groups of compounds intimately connected by isomorphism, the 

 molecular heat of the compounds increases and the molecular volume 

 decreases with increasing molecular weight of the compound or atomic 

 weight of the element. This will be shown by the following table, in 

 which the different isomorphous compounds, partly of yttrium, erbium, 

 and ytterbium, partly of lanthanum and didymium, are brought into 

 comparison : — 



* According to Cleve. 



f According to Nilson. 



