THE VALENCY AND SPECIFIC HEAT OF THE METALS 617 



Chapters III. and IV., a peroxide, Ba0 2 . 56 Neither calcium nor 

 strontium oxides are able to give such a peroxide directly, but they 

 form peroxides under the action of hydrogen peroxide. 



Barium oxide is decomposed when heated with potassium ; fused 

 barium chloride is decomposed, as Davy showed, by the action of a 

 galvanic current, forming metallic barium ; and Grookes (1862) obtained 

 an amalgam of barium from which the mercury could easily be driven 

 off, by heating sodium amalgam in a saturated solution of barium 

 chloride. Strontium is obtained by the same processes. Both metals 

 are soluble in mercury, and seem to be non- volatile or only very slightly 

 volatile. They are both heavier than water; the specific gravity 

 of barium is 3'6, and of strontium 2'5. They both decompose water at 

 the ordinary temperature, like the metals of the alkalis. 



Barium and strontium as saline elements are characterised by their 

 powerful basic properties, so that they form acid salts with difficulty, 

 and scarcely form basic salts. On comparing them together and with 

 calcium, it is evident that the alkaline properties in this group (as in 

 the group potassium, rubidium, caesium) increase with the atomic 

 weight, and this succession clearly shows itself in many of their corre- 

 sponding compounds. Thus, for instance, the solubility of the 

 hydroxides RH 2 2 and the specific gravity 57 rise in passing from 

 calcium to strontium and barium, while the solubility of the sulphates 



the cubical system, sp. gr. 5'74. SrO is obtained in the latter form from the nitrate. 

 The following are the specific gravities of the oxides from different sources : 



MgO CaO . SrO 



from RN 2 6 3'38 3'25 4'75 



KCO 3 8-48 8'26 4'45 



EH 2 O 2 8-41 8-25 4'57 



66 The property of barium oxide of absorbing oxygen when heated, and giving the 

 peroxide, BaO 2 , is very characteristic for this oxide (see Chapter III., Note 7). It only 

 belongs to the anhydrous oxide. The hydroxide does not absorb oxygen. Peroxides of 

 calcium and strontium may be obtained by means of hydrogen peroxide. Barium per- 

 oxide is insoluble in water, but is able to form a hydrate with it, and also to combine 

 with hydrogen peroxide, forming a very unstable compound having the composition. 

 BaH 2 4 (obtained by Professor Schone), which in course of time evolves oxygen (Chap- 

 ter IV., Note 21). 



57 Even in solutions a gradual progression in the increase of the specific gravity showp 

 itself, not only for equivalent solutions (for instance, KC1 2 + 200H 2 O), but even with an 

 equal percentage composition, aa is seen from the curves giving the specific gravi^ 

 (water 4 = 10,000) at 15 (for barium chloride, according to Bourdiakoff's detenninp.-. 

 tions) : 



BeCl 2 : S = 9,992 + 67-21jp + 0-lll2> 2 



CaCl 2 : S = 9,992 + 80'24jp + 0'476p 2 



SrCl 2 : S = 9,992 + 85'57# + 0'733p 2 



BaCl 8 : S = 9,992 + 86'56p + 0'813p 3 



