DiDYMIUM. 7 



Bromide ef didymium with bromide of zinc 



DùBr3 + 3ZnBr2+12H,0. 



According to Frerichs, and Smith the bromide of didymium gives 

 with the bromide of zinc a very deliqvescent double salt, crystallising 

 in radiated needles, having the composition 2DiBr3 + SZnBrg + SßHgO. 

 These authors say that the salt loses all its water (31.63 perc.) at 150" 

 and that the anhydrous salt, thus obtained, gave on analysis nearly all 

 the calculated quantity of bromine. This is very remarkable as hydro- 

 bromic acid may be evolved at the same time as the water and it is 

 scarcely probable that all the water could be lost at 150°. I have tried 

 to get the salt, described by Frerichs and Smith, but I obtained by slow 

 evaporating of the solutions of the mixed bromides, over oil of vitriol, 

 large, well formed, and rhombic tablets so extremely deliquescent, that 

 they could scarcely be freed from the thick mother-liquor. The salts 

 obtained from two different crystallisations were analysed. 



I. 1.0149 gram was mixed with acetate of sodium, and the zinc 

 precipitated with HjS. The precipitate was dissolved and precipitated 

 with NagCOs. The didymium was precipitated with ammonia, and the 

 solution of the hydroxide in nitric acid precipitated with oxalic acid. 

 0.1917 gram ZnO and 0.1402 gram DigOg were thus obtained. 



II. 0.7615 gram was precipitated with nitrate of silver, and the 

 filtrate, after separation of the excess of silver, treated as in analysis J. 

 1.0039 gram AgBr, 0.1440 gram ZnO and 0.1037 gram Di^Oj were obtained. 



In percent: 



I. 

 Di 11.82 



Zn 15.15 



Br — 



H,0 — 



1273 100.00 



