Chemistry and Physios. 493 



residue. These are: 15-93, 15-98, 15-98, 15-93, 15-92; the mean 

 of which is 15-95. Correcting for buoyancy, the final number for 

 the atomic mass of oxygen is 15-89. — Nature, xxxix, 462, March, 

 1889. G. F. B. 



2. On Diamide hydrate and other salts. — Cubitus and Jay 

 have continued their researches upon diamide N 2 H 4 , the com- 

 pound isolated in 1887 by the former chemist.* Its intense at- 

 traction for water has rendered its preparation in the anhydrous 

 condition extremely difficult ; especially since water is also set 

 free in all the reactions by which it is produced. On distilling 



diamide hydrochloride j -vttV 2 ' xsn\ with caustic lime in a silver 



retort, furnished first with a U-tube and then with a horizontal 

 tube filled with quicklime, the liquid hydrate collected in the re- 

 ceiver. A strong solution of potassium hydrate, however, gave 

 a larger yield. Diamide hydrate is a fuming liquid which boils 

 without change at 119° and has a high refractive power. Glass 

 is attacked by it readily and it rapidly destroys cork or caout- 

 chouc. It is strongly alkaline, has a taste like ammonia, with a 

 burning after-taste. It appears to be the strongest reducing agent 

 known. It precipitates silver from a cold concentrated solution 

 in fine compact crystalline masses and if the solution is dilute, in 

 splendid mirror-like films. Platinic chloride is completely reduced 

 by it with separation of metallic platinum. When dropped on 

 mercuric oxide it explodes violently. The salts of diamide are 



NH.HC1 



well-marked and very stable. The di-hydrochloride -\ ^rr 



strongly resembles ammonium chloride, crystallizing in cubes and 

 giving in films feathery crystals ; but it is deliquescent. On heat- 

 ing to 198° it fuses, evolves hydrogen chloride, and leaves a clear 



l "NJTT T4P1 



glass of mono-hydrochloride •] -vxtt 2 * . This on further heat- 

 ing breaks up into ammonium chloride, nitrogen and hydrogen. 

 The normal hydrochloride gives no precipitate with platinic 

 chloride but reduces it to platinous chloride, with evolution of 



nitrogen. Diamide sulphate \ ^tV* • H 2 S0 4 crystallizes in forms 



which are optically bi-axial. It is only sparingly soluble in cold 

 water and is thrown down when sulphuric acid is added to solu- 

 tions of its salts. It fuses at 254° and is decomposed almost ex- 

 plosively, evolving sulphurous oxide, hydrogen sulphide and sul- 

 phur and leaving ammonium sulphite. The carbonate, nitrate, 

 acetate and oxalate have also been obtained, all crystallized ex- 

 cept the first, and all having strong reducing properties. When 

 any salt of diamide is mixed with a nitrite, free nitrogen is 

 evolved almost explosively. — J. pr. Chem., xxxix, 27, 107; JBer. 

 Berl. Chem. Ges., xxii, 134 (Ref.), March, 1889. g. e. b. 



3. On the Synthesis of the Glucoses and of Mannite. — By the 

 action of barium hydrate upon acrolein dibromide E. Fischee and 



* This Journal, III, xxxiv, 226, Sept., 1887. 



