108 



L. P. NlLSON, 



4:0. From the basic salt, by treating with the quantity of acid 

 necessary for forming a) diselenite b) tetraselenite: 



3 / 2 -selenite: a) 2[Al 2 .O s .3SeO] + 3H 2 .0 2 .SeO + 9H 2 0. 



2[In 2 . 6 . 3SeO] + 3H 2 .0 2 .SeO + 1 2H 2 0. 

 b) 2[Di 2 .0 G .3SeO] + 3H 2 .0 2 .SeO + 18H 2 0. 



5:o. From the basic salt, by treating with the quantity of acid 

 necessary for forming tetraselenite: 



5 / 8 -s el eni t e : Cr 2 .0 G .3SeO -f 2H 2 .0 2 .SeO + 7H 2 0. 



La 2 .O c .3SeO + 2H 2 .0 2 .SeO + 4H 2 0. 



G:o. From the basic salt by treating with the quantity of acid 

 necessary for forming tetraselenite: 



diselenite: Al 2 .0 6 .3SeO -f 3H 2 .0 2 .SeO + 2H 2 0. 



Ce 2 .0 6 .3SeO + 3H 2 .O'.Se0 + 2H 2 0. 

 La 2 6 .3SeO + 3H 2 .0 2 .SeO + 4H 2 0. 

 In 2 .0 6 .3SeO 4- 3H 2 2 .SeO + 4H 2 0. 



As the above salts, which, within the different groups, very often 

 agree even as to the amount of water, have been formed under circumstan- 

 ces that may be called absolutely the same, I think we may safely infer 

 from this, that the metals, contained in them, have a similar quantivalence. 

 If, consequently, iron, chromium, aluminium are unquestionably quadrivalent 

 with sexivalent double-atoms, it is also necessary that cerium, lanthanum, 

 didymium, yttrium, erbium, indium must share this property, on account of 

 a correspondence in the composition of compounds, formed under the same 

 circumstances, as complete as can be desired. 



In the course of his researches on the earth-metals, Cleve x ) says 

 that he has found "by no means convincing reasons for the sexivalence of 

 the metals mentioned such as the composition of didymiumchloraurate 

 2DiCl 3 -f3AuCl 3 , the amount of water in the acetates of cerium and lan- 

 thanum, the natrium-didymium-carbouate 2Di 2 ^C0 3 ) 3 -+- 3(Na 2 C0 3 ) and some 

 doublesulphates of kalium"; on account of other data, he is therefore of 

 opinion that they are trivalent, and consequently for instance writes the 

 formula of the chlorides RC1 3 . 



The palpable analogy between the above mentioned salts seems to 

 place it, however, beyond all doubt, that they do not possess this valence, 



') Bib. t. Sv. Vet. Akad. handl. 2 N:o 12 s. 92. 



