66 Scientific Intelligence. 



the alkali metal in brilliant crystals, as Seely long ago pointed 

 out. As opinions differ as to whether these metallic ammoniums 

 are molecular or atomic in constitution, the author has made 

 experiments with potassium, sodium, lithium and calcium. Each 

 metal was placed in a U-tube of glass, one leg of which was 

 drawn out tine, while the other was recurved and connected with a 

 source of ammonia gas, dried first over fused potassium hydrate 

 and then over sodium. The four tubes were united successively 

 so that the same current of ammonia gas traversed them all. By 

 the use of a water bath, the temperature could be regulated, and 

 the flow of gas increased or diminished by means of a tap. For 

 low temperatures acetone was used in the bath, being cooled even 

 as low as — 75°, the solidifying point of ammonia, by adding to 

 it fragments of solid carbon dioxide. The experiments were 

 made under atmospheric pressure. It was found that lithium was 

 attacked at +70° with liquefaction, calcium at +20° without 

 liquefaction, potassium at — 2° with liquefaction, and sodium at 

 20° with liquefaction. It is clear therefore that these four metals 

 unite directly with ammonia gas, the temperatures obtained being 

 the superior limits of the action and at the same time the decom- 

 position-temperatures of the metallic ammoniums under the 

 conditions. By preparing the metallic ammonium by the action 

 of the liquefied gas, and then slowly raising the temperature, the 

 inverse method was effected, the sodammonium dissociating at 

 — 20° and giving the metal and ammonia gas, and the potassam- 

 monium doing the same at — 2° ; while calcium-ammonium and 

 lithium-ammonium were stable at the ordinary temperature and 

 pressure. Moreover, ammonia gas solidified at — 80°, does not 

 attack either of the four metals, though action takes place as soon 

 as liquefaction commences with evolution of heat. If the experi- 

 ment is made slowly, the author states that amides of these 

 metals are produced ; while when it is rapid, the metallic ammo- 

 nium may be readily produced at the ordinary pressure and the 

 metal regenerated in crystals without the production of amides. 

 Lithium placed in a U-tube at the temperature of the laboratory 

 and subjected to a current of ammonia gas, takes a brownish-red 

 tint and liquefies, producing a liquid of the same color. Heated 

 rapidly to + 70°, the excess of ammonia escapes, leaving a reddish- 

 brown solid, which takes fire in contact with the air. If lithium 

 be placed in liquefied ammonia, the tube being allowed to return 

 slowly to the ordinary temperature, the dark blue liquid becomes 

 thicker, reaching a sensibly constant composition after 24 hours. 

 The composition then was found to be : NH 3 89*04, 87'00, 88*72, 

 and 88*37 in four samples; the formula (NH 3 ) 3 Li requiring 87*93. 

 The liquid may therefore be considered either as a saturated solution 

 in ammonia gas or as a compound NH 3 Li.(NH 3 ) 2 . As to solid lith- 

 ium-ammonium, its composition was determined (1) by weighing 

 the ammonia fixed by the metal and (2) by preparing the com- 

 pound and determining the ammonia in it. The lithium found in 

 five experiments was 28*07, 28*40, 28*72 and 28*82 per cent. ; the 



