262 IIarti-ey — The Action of Heat, on the Absorption Spectra and 



It is necessary here to give an account of the hydrates of nickel bromide and 

 iodide, in order to explain the nature of the action of heat upon their absorption 

 spectra and the constitution of their solutions. 



Preparation and Analysis. Nickel Bromide and its Hydrates. 



These salts have been but imperfectly described by Berthemot* and by 

 Rammelsberg.f 



Tlie analj^sis of the latter lead to a formula for the crystallized liydrated salt 

 of NiBrs'^iHoO. I have not obtained this as a crystallized salt. 



The bromide was prepared in a similar manner to that described for tlie 

 preparation of haloid cobalt salts.J 



Clippings of rolled nickel were placed in a platinum dish with water and some 

 bromine, and kept in a warm place. The green solution obtained was filtered and 

 evaporated, and finally crystallized by allowing it to remain in a bell-jar standing- 

 over sulphuric acid. 



Well-formed green crystals were obtained which, while they were very deli- 

 quescent in the air, rapidly effloresced over sulphuric acid. In this respect they 

 resemble cupric bromide. The only way they could be dried was by crushing 

 rapidly between folds of blotting paper. The water of crystallization was esti- 

 mated in the usual way by heating in the steam-oven and weighing at repeated 

 intervals. The nickel was estimated by precipitating a solution boiled in a 

 platinum dish with potassium hydroxide, and igniting the precipitate in a 

 platinum crucible at a bright red-lieat over a blow-pipe. The bromine was, of 

 course, determined gravimetrically as silver bromide. 



The composition of the salt is NiBrj-eHoO as the following figures sliow: — 



Determination of tlie Water. 



I. II. 



Salt taken for analysis 3-5978 2-3960 



Lossonheating to 100° C. till -(v eight oonstaut, . l-'2045 ()-7957 



HoO per cent., 33-47 33-21 



Determinations of Nickel and Bromine. 



I. II. III. 



Weight of salt taken, 0-4347 0-8727 1-2382 



Weight of NiO preoipitatod, .... 0-1042 0-1990 — 



Ni per cent, 18-83 17-92 — 



"Weight of AgBr precipitated, .... — — 1-4143 



Weight of Br — -- 0-6019 



Br per cent., — — 48 61 



*Ann. Chim. Phys,, vol. 44, p. 389. fPogg. Annalen, vol. 5.*), p. 243. J Jour. Chera. Soc., vol. 12, 1874. 



