SODIUM 539 



The most important chemical property of sodium is its power of 

 easily decomposing water and evolving hydrogen from the majority of 

 the hydrogen compounds, and especially .from all acids, and hydrates 

 in which hydroxyl must he recognised. This depends on its power of 

 combining with the elements which are in combination with the 

 hydrogen. We already know that sodium disengages hydrogen, not 

 only from water, hydrochloric acid, 44 and all other acids, but also from 

 ammonia, 44 bis with the formation of sodamide NH a Na, although it 

 does not displace hydrogen from the hydrocarbons. 48 Sodium burns 



44 H. A. Schmidt remarked that perfectly dry hydrogen chloride is decomposed 

 with great difficulty by sodium, although the decomposition proceeds easily with potas- 

 sium and with sodium in moist hydrogen chloride. Wanklyn also remarked that sodium 

 burhs with great difficulty in dry chlorine. Probably these facts are related to other 

 phenomena observed by Dixon, who found that perfectly dry carbonic oxide does not 

 explode with oxygen on passing an electric spark 



44 *> Sodamide, NH 2 Na, (Chapter IV.. Note 14), discovered by Gay-Lussac and 

 Thenard, has formed the object of repeated research, but has been most fully investigated 

 by A. W. Titherley (1894"). Until recently the following was all that was known about 

 this compound : 



By heating eodium in dry ammonia, Gay-Lussac and The'nard obtained an olive- 

 green, easily- fusible mass, sodamide, NH 2 Na, hydrogen being separated. This substance 

 with water forms sodium hydroxide and ammonia ; with carbonic oxide, CO, it forma 

 sodium cyanide, NaCN, and water, H 2 O ; and with dry hydrogen chloride it .forms sodium 

 and ammonium chlorides* These and other reactions of sodamide show that the metal 

 'in it preserves its energetic properties in reaction, and that this compound of sodium is. 

 jnore stable than the corresponding chlorine amide. When heated, sodamide, NH 2 Na, 

 only partially decomposes, with evolution of hydrogen, the principal part of it giving 

 ammonia and sodium nitride, NasN, according to the equation 8NH2Na=2NH5 + NNa 3 . 

 The latter is an almost black powdery mass, decomposed by water into ammonia and 

 sodium hydroxide. 



Titherley's researches added the following .data : 



Iron or silver vessels should be used in preparing this body, because glass and 

 porcelain are corroded at 800-400, at which temperature ammonia gas acts upon 

 sodium and forms the amide with the evolution of hydrogen. The reaction proceeds 

 elowly, but is complete if there be an excess of NH 3 . Pure NH 2 Na is colourless (its 

 colouration is due to various impurities), semi-transparent, shows traces of crystallisation, 

 has a conchoidal fracture, and melts at 145. Judging from the increase in weight of 

 the sodium and the quantity of hydrogen which is disengaged, the composition of the 

 amide is exactly NH 2 Na. It partially volatilises (sublimes) in vacuo at 200, and breaks 

 up into 2Na + N 2 + 2H 2 at 600. The same amide is formed when oxide of sodium is 

 heated in NH 5 : NaaQ-f 2NH 3 =2NaH 2 N + H 2 O. NaHO is also formed to some extent 

 by the resultant H 2 O. Potassium and lithium form similar amides. With water, 

 alcohol, and acids, NH 2 Na gives NH 5 and NaHO, which react further. Anhydrous CaO 

 absorbs NH 2 Na when heated without decomposing it. When sodamide is heated with 

 CiO 2 , NHj is disengaged, and silicon nitride formed. It acts still more readily upon 

 fcoric anhydride when heated with it: 2NH 2 Na+B 2 O 3 = 2BN + 2NaHO + H 2 O. When 

 slightly heated, NH 2 Na--NOCl=NaCl + N 2 -f H 2 O (NHNa 2 and NNa 3 are apparently not 

 formed at a higher temperature). The halogen organic compounds react with the aid 

 Of heat, but with so much energy that the reaction frequently leads to the ultimate de- 

 struction of the organic groups and production of carbon. 



45 As sodium does not displace hydrogen from the hydrocarbons, iiviay be preserved 

 in liquid hydrocarbons. Naphtha is generally used for this purpose, as it consists of a 

 mixture of various liquid hydrocarbons. However, in naphtha sodium usually becomes 

 coated with a crust composed of matter produced by the action of the sodium on certain 



