84 Dr. Odling, on Magnesium, Calcium, [March 11, 



is quickly oxidised in the air, is rapidly acted upon by water, and is 

 not obtainable by treating its chloride with sodium. The hydrate of 

 calcium is soluble in water, the hydrates of magnesium and of zinc 

 insoluble. Hydrated chloride of calcium, when heated, evolves 

 water, but the hydrated chlorides of magnesium and zinc evolve 

 chlorhydric acid, &c. 



Lithium is a very sparingly distributed element. It occurs native, 

 in proportions varying from 3 to 12 per cent., in certain complex 

 silicates, fluorides, and phosphates ; and is obtained in the metallic 

 form by the electrolysis of fused chloride of lithium. The specific 

 gravity of lithium is 0"59. With the exception of bodies in the gaseous 

 state, it is the lightest substance in nature. It floats upon every known 

 liquid. One cubic inch of platinum balances 36^ cubic inches of 

 lithium. Lithium is a white-coloured lustrous metal, rapidly oxidised 

 by exposure to the air. It is softer than lead, and may be cut with a 

 knife, or squeezed between the fingers. It is readily obtained in the 

 form of wire, by Matthiessen's process. It melts at 180°C, and at a 

 higher temperature volatilizes. When heated to redness in the air, 

 lithium takes fire, and burns with a brilliant, highly luminous, white 

 flame, that is in curious contrast with the crimson colour which its 

 compounds impart to the flame of ordinary combustibles. The pre- 

 sence of lithium in any substance is usually ascertained by means of 

 this crimson-coloured flame, which, however, is altogether irrecog- 

 nizable in the presence of even a small quantity of sodium salts, owing 

 to the intense yellow-coloured flame which they produce. Cartmell 

 has recently pointed out a ready mode of detecting the lithium colora- 

 tion, even in the presence of a large excess of sodium salts, namely by 

 viewing the flame through a layer of the blue solution of sulphate of 

 indigo, which completely cuts off the yellow rays due to the sodium, 

 but allows the uninterrupted transmission of the crimson rays due to 

 the lithium. Gradational relations, similar to those of magnesium, 

 zinc, and cadmium, exist between lithium, sodium, and potassium. In 

 the solubility of its carbonate, in its degree of oxidisability, and in 

 many other properties, sodium is strictly intermediate between its two 

 congeners. De la Rue has observed, that metallic sodium from its 

 inferior degree of oxidisability, may be preserved unacted upon in an 

 aqueous solution of caustic soda. The atomic weight and atomic 

 volume of sodium are respectively the means of the atomic weights 

 and atomic volumes of lithium and potassium. 



Lithium undoubtedly belongs to the same family as sodium and 

 potassium. Like these two metals it is soft, readily fusible and 

 volatile, highly oxidisable, and of lower specific gravity than water. 

 Moreover, its hydrate and carbonate are sensibly soluble in water. 

 But having regard to the totality of its characters in the free and com- 

 bined states, and particularly to the properties of its hydrate, carbonate, 

 and phosphate, it appears that the analogies of lithium to calcium and 

 magnesium respectively, are scarcely less marked than are its relations 

 to the true alkaline metals. It seems, indeed, as if the metals 

 lithium, calcium, and magnesium stood upon the same level, and that 



