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XIIL- On Crystallized Sodium and Potassium.

BY CHARLES EDWARD LONG.

IN endeavouring to prepare perfectly bright specimens of sodium and potassium, I have succeeded in obtaining large crystals of

I will briefly describe the method now employed. both metals. A piece of the best combustion

tube about 2+ feet in length, and 2-inch in bore, is sealed up at one end, and contracted before the blow- pipe at about one-third of its length horn the sealed end (fig. 1). A glass funnel with a wide rim (fig. 2) is then prepared so as to fit into the tube as represeuted, care being taken that the funnel fits at the rim alone. Into the filter is introduced a piece of wire gauze, in which a small hole has been cut at a (fig 2). The sodium (or potassium) is now intro- duced into the upper part of the tube in fragments \\hich have been freed from all adhering oxide, and especially from rock-oil, by cutting the metal clean with a knife. Before introducing the metal, the tube is filled with coal-gas which has been dried and partly purified by passing through sil of vitriol. For this

purpose, the delivery tube is passed through the tube b, which is fitted with a cork into the larger tube.

After the introduction of the metal, the gas is still passed into the tube; the delivery tube is then drawn out and the tube b is lightly corked, The large tube is now drawn out and sealed before the blowpipe at c, care being taken to avoid melting the metal, lest it should attack the glass and render it brittle. The metal is next fused in the upper part of the tube, and partially

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LONG ON CRYSTALLIZED SODIUM AND POTASSIUM. 123

poured off from the oxide, so as to present a bright surface for the absorption of any oxygen there may be in the tube. The whole is then allowed to stand for several days, after which the metal is again melted, poured through the filter into the lower portion of the tube, and allowed to solidify. The tube is now cautiously heated at d, so as to detach the rim of the filter, which will then readily fall back to the top of the tube on reversing its position, leaving a perfectly clean surface of tube o i about 3 inches. The lower tube may now be drawn out and sealed at e.

In this manner either metal may be obtained without the slightest tarnish or oxidation. In order to crystallise the metal, it is fused over a Bunsen's lamp, and allowed to cool; as soon as the solid points of crystals appear on the surface, the liquid portion is poured off by suddenly inclining the tube. Specimens prepared in this manner 18 months ago, still retain their lustre unimpaired.

Sodium-Sodium presenting a perfectly clean metallic surface, is not silver-white, but is of a most beautiful rose colour. The colour is best seen when a ray of light falling upon a surface of the metal is reflected back from a second surface of sodium, and again reflected from the first, so that more of the light of the primitive ray is decomposed than by direct reflection, since the great number of undecomposed reflected rays entirely masks the small number of pink rays, as is the case with silver, which is really yellow and not white. The pink colour of sodium is brought out more strongly by contrasting the metal with bright potassium, which has a greenish-blue tinge.

It does not crystallise in the regular s p t e m , but most probably in tt-e quadratic system. As it is impossible to meastire the crystals by reflection, o ~ i n g partly to their being enclosed in a glass tube, but chiefly to the irregularity of the faces which are always striated in a direction at right angles to the major axis, I was only able to measure the facial angles by using a narrow tube provided with an arc, and across which a fine hair was stretched. Ilrifortunately I have not obtained any crystals with the base-angles well defined. The following are measurements of the angle of the apex :-

Sodium is obtained in large octahedra by crystallisation,

Angle of apex. I

1 2 3 Crystal I. face a . . 49O.8 5OO.O 50O.5

faceb . . 50"-5 50"*0 49O.5 Crystal 11. . . 49" 5 50"-0 49"*5

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124 WANKLYN ON ZINC-BIETHYL.

- Potassium-Has a greenish or greenish blue tint. The beauti- ful green colour of the vapour may be observed by volatilizing a small portion of the metal in a sealed tube contaiiiing no oxygen. It is much more crystalline metal than sodium, but is more difficult to obtain in good crystals, since it passes almost imme- diately from the liquid to a pasty state. The crystals present an almost smooth metallic appearance for a few moments after the liquid metal has been pourd off. Suddenly they assume the appearance of frosted silver, a network of minute lines darting out in every direction. For this reason, they disperse light much more than sodium crystals, whereby the real colour of the metal is e ffec tuallp rn asked.

Potassium crystallises in obtuse octahedra belonging to the quadratic system. Tlre following are the measurements of the three facial angles of one of the crystals. only able to measure one of the angles of the base :-

I n crystal

1 2 5.2'*0 52'9 !$ 52O.O 52"*0 Crystal I. Angles of base

Angle of apex y 7 5 O . 5 7 5 O . 8 1 2 3

Crystal 11. Angle of base 52'-0 51'5 51"*8

11, I was

3 52O.O 52O.O 76O.O

4 51O-8

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