THE VALENCY AND SPECIFIC HEAT OF THE METALS 619 



an analogy to aluminium oxide in the same way that lithium oxide is 

 analogous to magnesium oxide. 60 Owing to its rare occurrence in nature, 

 to the absence of any especially distinct individual properties, and to 

 the possibility of foretelling them to a certain extent on the basis of the 

 periodic system of the elements given in the following chapter, and 

 owing to the brevity of this treatise, we will not discuss at any length 

 the compounds of beryllium, and will only observe that their 

 individuality was pointed out in 1798 by Vauquelin, and that 

 metallic beryllium was obtained by Wohler and Bussy. Wohler 

 obtained metallic beryllium (like magnesium) by acting on beryllium 

 chloride, BeCl 2 , with potassium (it is best prepared by fusing 

 K 2 BeF 4 with Na). Metallic beryllium has a specific gravity 1*64 

 (Nilson and Pettersson). It is very infusible, melting at nearly 

 the same temperature as silver, which it resembles in its white 

 colour and lustre. It is characterised by the fact that it is very diffi- 

 cultly oxidised, and even in the oxidising flame of the blowpipe is only 

 superficially covered by a coating of oxide ; it does not burn in pure 

 oxygen, and does not decompose water at the ordinary temperature or 



60 Beryllium oxide, like aluminium oxide, is precipitated from solutions of its salts 

 by alkalis as a gelatinous hydroxide, BeH 3 O 2 , which, like alumina, is soluble in an excess 

 of caustic potash or soda. This reaction may be taken advantage of for distinguishing 

 and separating beryllium from aluminium, because when the alkaline solution is diluted 

 with water and boiled, beryllium hydroxide is precipitated, whilst the alumina remains 

 in solution. The solubility of the beryllium oxide at once clearly indicates its feeble 

 basic properties, and, as it were, separates this oxide from the class of the alkaline earths. 

 But on arranging the oxides of the above-described metals of the alkaline earths accord- 

 ing to their decreasing atomic weights we have the series 



BaO, SrO, CaO, MgO, BeO, 



in which the basic properties and solubility of the oxides consecutively and distinctly 

 decrease until we reach a point when, had we not known of the existence of the beryllium 

 oxide, we should expect to find in its place an oxide insoluble in water and of feeble basic 

 properties. If an alcoholic solution of caustic potash be saturated with the hydrate of 

 BeO, and evaporated under the receiver of an air pump, it forms silky crystals BeKjOg. 

 Another characteristic of the salts of beryllium is that they give with aqueous am- 

 monia a gelatinous precipitate which is soluble in an excess of ammonium carbonate 

 like the precipitate of magnesia; in this beryllium oxide differs from the oxide of 

 aluminium. Beryllium -oxide easily forms a carbonate which is insoluble in water, and 

 resembles magnesium carbonate in many respects. Beryllium sulphate is distinguished 

 by its considerable solubility in water thus, at the ordinary temperature it dissolves 

 in an equal weight of water ; it crystallises out from its solutions in well-formed crystals, 

 which do not change in the air, and contain BeSO 4 ,4H 2 O. When ignited it leaves 

 beryllium oxide, but this oxide, after prolonged ignition, is re-dissolved by sulphuric acid, 

 whilst aluminium sulphate, after a similar treatment, leaves aluminium oxide, which is 

 no longer soluble in acids. With a few exceptions, the salts of beryllium crystallise with 

 great difficulty, and to a considerable extent resemble the salts of magnesium ; thus, for 

 instance, beryllium chloride is analogous to magnesium chloride. It is volatile in an 

 anhydrous state, and in a hydrated state it decomposes, with the evolution of hydro* 

 'chloric acid. 



