292 F. W. Clarke— Note on Molecular Volumes. 



The writer has also determined the specific gravities of 

 several alkaline fluorides, as follows: Lithium fluoride, 2*296, 



21-.V: sodium fluoride, 2'558, 14-5°; potassium fluoride, 2-096, 



21-5°. According to Bodeker, potassium fluoride has a density 



at 12°. Theoretical considerations, to be cited in the 



third part of t! is j ap< r, sustain the lower value ; - obtained by 



l fluoride, made i 



ntity of material, may not prove to be wholly trust- 

 It gave a specific gravity of 3-102 at 17°. Eubidium 

 carbonate was dissolved in hydrofluoric acid, the solution evap- 



orated to dryness in a platinum dish, and the residue fused i 

 a heat just below redness. The molten fluoride was so trans- 

 parent as to be almost invisible in the vessel containing- it : but 

 upon cooling, it became white and opaque, and contracted so 

 strongly as to split up into several fragments. This salt is ex- 

 tremely deliquescent. 



Attempts to prepare fluorides of gold and platinum were wholly 

 unsuccessful. Still, results were obtained which may be worth 



ution of gold chloride, silver fluoride i 

 by double de 



oposition silver chloride 

 might be thrown down and gold fluoride formed. In fact, 

 however, there fell a pale-brown precipitate which grew rapidly 

 darker in color, and which consisted of silver chloride mixed 

 with gold oxide. The reaction mav be expressed as follows: 



2AuCl 3 +6AgF+3H 2 0=Au 2 3 + 6AgCl+6HF. 

 With platinum tetrachloride and silver fluoride a pale-yellow 

 precipitate was formed, containing platinum dioxide, thus: 



PtCl 4 +4AgF+2H 2 0=Pt0 2 +4AgCl+4HF. 

 The same precipitates are formed when silver nitrate is used 

 instead of fluoride, nitric acid being set free in place of hydro- 

 fluoric. This has long been known, the reactions being new 

 only in so far as they involve the effect of silver fluoride. This 

 statement is made so that perhaps some ot 

 3 expert 



o that perhaps some other investigators may 

 ed from tedious and fruitlei 



III. Note on Molecular Volumes. 

 Several years ago, in a series of papers upon atomic or molec- 

 ules, I pointed out some curious multiple relations 

 J both elements and compounds.* For example, I 

 i a simple relation of this kind connected thi 

 metals with each other; and, later, that the haloid salts of 

 some of these metals had moleeu ; ies of that 



of hydrogen. For this latter relation, however, mv material* 

 were meager. I had then the specific gravity determinations 

 * This Journal, March and May, 1869; September, 1870. 



