106 



L. F. Nilson, 



Among the metals above treated, chromium and lanthanum have 

 given 5 / 3 -selenites; consequently, uranium shows a certain analogy with them. 



If Ave comprize in a general view the data resulting from the re- 

 searches on the selenites of the metal-group treated of in the preceding 

 pages, very interesting and remarkable conclusions may be arrived at. 



First it is worth notice that most of the neutral solutions of these 

 metals afford basic salts by precipitating with neutral selenite of sodium. 

 Excluding uranium, as being single in its kind, it is only yttrium and 

 erbium which by this treatment give neutral salts; indium like aluminium 

 and chromium has given 3 / 4 -sclenite; cerium 5 / 6 -selenite; iron didymium and 

 lanthanum 8 / 9 -selenites. Except in the case of yttrium and erbium, neutral 

 salts have been produced by treating the basic ones with quantities of sele- 

 nious acid calculated for the purpose and weighed oft to the nearest milli- 

 gram in form of anhydride; the acid salts mentioned have been obtained 

 in the same way, and the temperature at which the solutions were digested, 

 has been the same in all experiments, the small glass-vessels in which the 

 reaction took place, being placed immediately upon an air-bath, which al- 

 ways showed a temperature of 100°. The homogeneous quality of the 

 salts was in every case determined by means of microscopical examination, 

 so that no mixtures of salts were possible. These acid salts, all of which 

 crystallized more or less distinctly, present a very remarkable composition. 

 Under accurately the same circumstances, viz. 1 mol. neutral salt 

 being treated with 3 mol. selenious acid, chromium, iron, yttrium, erbium, 

 cerium and didymium have given 4 / 3 -selenites [it is remarkable, that this 

 is not the case with lanthanum]; aluminium indium and didymium have 

 afforded sesqui-selenites, both the former when diselenite, the latter 

 when tetraselenite might have been formed; chromium and lanthanum have 

 given 5 / 3 -s elenites, when the proportion between base and acid allowed 

 the formation of tetraselenites, and aluminium, cerium lanthanum and indium 

 have under the last mentioned circumstances formed di selenites; but no 

 one of the metals in question has given salts more acid than di- 

 selenite. 



A better survey of these circumstances and of the corresponding 

 composition of the products, obtained in the different cases, is given in the 

 subjoined tables. 



