"Pure sodium is a lustrous metal, at the ordinary temperature as white as silver and as soft as wax, but it becomes brittle in the cold. In ordinary moist air it quickly tarnishes and becomes covered with a film of NaHO and Na2CO3, formed at the expense of the water and CO2 in the air. In perfectly dry air sodium retains its lustre for an indefinite time. Its density at the ordinary temperature is equal to 0.975, so that it is lighter than water; it fuses very easily at a temperature of 97°, and distils at a bright red heat (742°, according to Perman, 1889). Scott (1887) determined the density of sodium vapour and found it to be nearly 12 (if H = 1). This shows that its molecule contains one atom (like mercury and ), Na. It fuses with most metals, forming indefinite compounds called s. Thus, if sodium, having a clean surface[,] be thrown into mercury, especially when heated, there is a flash, and such a considerable amount of heat is evolved that part of the mercury is transformed into vapour. Compounds or solutions of sodium in mercury, or amalgams of sodium, even when containing only 2 parts of sodium to 100 parts of mercury, are solid. Only those amalgams which are the very poorest in sodium are liquid. Such alloys of sodium with mercury are often used instead of sodium in chemical investigations, because in combination with mercury sodium is not easily acted on by air, and is heavier than water, whilst at the same time it retains its principal properties, such, for instance, as the power to decompose water, forming NaHO."