( '/<> m istr-y 'tin/ I V///.v/r.v. 8 1 5 



between 440 and 600° appears to have a point of inflexion oorre- 



nding to a maximum dissociation. He thinks the most natural 



conclusion to be that like amylerie bromhydrate, aluminum ohlo- 



ride has two vapor-densiiies ; one between 200° and 400° corre- 



•nding to the formula A1XJ1,, and a second above 800°, corre- 

 sponding to the formula AIC1,. — Ann. Chim. Phys. y VI, \ix, 145, 

 171, February, 1890. o. p. b. 



3. On t/it Combination of Potassium and Sodium with Am- 

 *nia. — Joannis has observed that when an equivalent mass of 



alkali-metal is dissolved in twenty times the equivalent mass of 

 liquefied ammonia, and the ammonia is gradually removed, the 

 pressure falls very rapidly, becoming after a certain time con- 

 stant and equal to 170" ,,u at 0°. The residue lias the composition 

 Na + 5'S NHj ; but since the proportion of ammonia varies with 

 the temperature, it is probably not a definite compound. As 

 more ammonia is removed, a dark red solid substance, darker 

 even than copper, is deposited from the red solution, the pressure 

 remaining constant. Finally, when one equivalent mass of am- 

 monia to one of metal remains, the liquid has completely disap- 

 peared and there is left only solid sodium-ammonium or potassium- 

 ammonium. On reducing the amount of ammonia still further, 

 the free alkali-metal gradually separates, the pressure remaining 

 uniform; a dissociation therefore taking place, the pressure of 

 which is equal to that of the saturated solution. — C. P., cix, 900, 

 Dec, 1889. g. f. b. 



4. On the Preparation of Platinic fluoride. — Moissan has suc- 

 ceeded in preparing anhydrous platinic fluoride by passing a cur- 

 rent of fluorine over a bundle of platinum wires contained in a 

 tube of platinum or fluor spar, heated to 500° or 600°, and con- 

 densing the product in a dry glass vessel. The fluoride forms a 

 dark-red mass either fused or made up of chamois-colored crystals. 

 It is very hygroscopic and yields a yellow solution with water, 

 which almost instantly decomposes with evolution of heat, yield- 

 ing platinic hydroxide and hydrogen fluoride. It is thus made 

 evident why platinic fluoride has not been obtained in the wet 

 way. On heating to redness platinic fluoride decomposes readily, 

 yielding pure fluorine and crystallized platinum; thus furnishing 

 the best method of obtaining fluorine pure. Gold treated in a 

 similar way yields a similar fluoride. — C. P., cix, 80V, Nov., 1889. 



G. P. 11. 



5. On Xylose or Wood-sugar, a new Penta-glycose. — Wheeler 

 and Tollexs have examined the sugar discovered by Koch in 

 wood and called xylose. It was prepared by the hydrolysis 

 of wood-gum, obtained from beech wood. The saw dust from 

 this wood, after extraction with ammonia was digested with 

 a five per cent soda solution for 48 hours and precipitated 

 with 95 per cent alcohol. After washing with acidulated al- 

 cohol, the precipitate was treated with ether, and the residue, 

 dried over sulphuric acid, left a porous mass almost colorless. 

 To prepare the xylose 50 grams of this gum were boiled with 



