F. W. Clarke— Notes upon some Fluorides. 291 



II. Notes upon some Fluorides. 



Nickel fluoride.— -This salt was prepared by dissolving nickel 

 hydrate in aqueous hydrofluoric acid. Upon concentrating the 

 dark green fluid agranular mass of crystals separated out ; which. 

 according to water (let Mr John Hagemann, 



had the composition NiF 3 .3H 3 0. The last portions of water 

 were retained up to the temperature of 130°. Percentage of water 

 found, 35-98 ; calculated, 35-81. Specific gravity, 2 014 at 19°. 

 The anhydrous fluoride, NiF 3 , had the density 2-855 at 14°. 

 These specific gravity determinations were made in an ordinary 

 specific-gravity bottle, chloroform being the liquid employed. 



On two accounts these observ _r. First, 



because the hydrated salt is evidently new, the crystallized 

 nickel fluoride described by Berzelius having contained but 

 two molecules of water. Secondly, the molecular volume of 

 the water in this new hydrate is" 13"65 ; corresponding very 

 closely, with the average value of 13 -76, deduced bv the writer 

 from the study of over thirty different salts, and stated in his 

 paper of two years ago.* 



Attempts to prepare a double fluoride of nickel and silver 

 met with but indifferent success. In several experiments the 

 mixed solutions of the two fluorides yielded upon concentrating 

 only the nickel salt alone; the silver compound apparently 

 decomposing. In one instance, however, pale apple-green 

 needles were deposited, mixed with some microscopic rhombo- 

 nedrons. Upon recrystallizing, about two-tenths of a gram of 

 these crystals were obtained, both forms being represented, and, 

 to the naked eye, both consisting of one and the same substance. 

 A qualitative examination showed them to be a true double 

 fluoride of nickel and silver, highly hydrated ; but not sufficient 

 m quantity for a thorough analysis. The silver in them 

 amounted to a trifle less than twenty per cent, a proportion 

 which agrees with no probable formula. 



. ?inc fluoride.— The only new fact forme to record concerning 

 this salt is its density. Two distinct samples of the crystallized 

 compound, ZnP 3 .4H 2 0, obtained from a solution of zinc in 

 Mfofluoric acid, gave respectively 2%567 at 10°, and 2*535 at 

 V • The anhydrous fluoride gave in one experiment a spe- 

 cific gravity of 4-556 at 17°, and in another 4-612 at 12°. 

 J-hese figures are noticeable from the fact that they do not 

 agree with the usual molecular volume of water of crystalliza- 

 tj on. They yield a volume of water ranging from 114 to 11-8 ; 

 fn amount considerably below the usual value. I will not now 

 hazard anv conjectures as to the meaning of this apparent 

 exception." 



