216 Dr. llolziuaun on some Cerium Compounds. 



Carbonic acid . . 



. . 1791 



Carbonic oxide . . 



. . 18-94 



Air 



. . 63-15 



10000 

 From which we see that little or no change in the relative 

 proportions of G 2 and Q had taken place, — a circumstance 

 tending to prove that the exit of gas, en masse, is due to currents 

 and not molecular. 



XXVII. On some Cerium Compounds. 

 By M. IIolzmann, Ph.D.* 



ON continuing my former researches on the cerium com- 

 poundst,I found a new class of double nitrates of cerium 

 which do not contain the cerium in the state of protosesquioxide, 

 but simply as protoxide. I prepared the cerium double salts of 

 ammonium, potassium, strontium, magnesium, zinc, manganese, 

 nickel, cobalt, and uranium, partly by dissolving the metal in a 

 solution of nitrate of protosesquioxide of cerium containing a 

 considerable quantity of free acid, partly by mixing the solutions 

 of the two nitrates. The deoxidation of the protosesquioxide of 

 cerium was effected in the first case by the hydrogen generated 

 in dissolving the metal ; in the second by boiling the nitrate of 

 protosesquioxide of cerium with alcohol. If the solution of 

 the cerium-salt contains an excess of nitric acid, the alcohol must 

 be added in small quantities, as the disengagement of gas causes 

 a violent ebullition. The analyses of the ammonium, magnesium, 

 zinc, manganese, nickel, and cobalt salts were already finished, 

 when a paper was published by L. Th. LangeJ, in which the 

 same salts are described, — in consequence of which I have dis- 

 continued my research, and will now only state those of my ob- 

 servations which do not agree with Lange's. 



The double salt of nitrate of cerium and nitrate of magnesium, 

 prepared by myself, is not of a pale pink colour, but perfectly 

 colourless, and only contains six atoms of water of crystal- 

 lization. As this composition differs from that of the other salts 

 belonging to the same group, I analysed the products of several 

 preparations, but always obtained the same results. The salt 

 was obtained by mixing equal parts of concentrated solutions of 

 nitrate of magnesium and nitrate of protoxide of cerium, and 

 leaving the mixture to crystallize over caustic lime and chloride 

 of calcium. The crystals, representing perfectly developed hex- 



* Communicated by the Author. 



t Journal fur Praktische Chemie, vol. lxxv. p. 321. 



X Ibid. vol. lxxxii. p. 129. 



