TIH-: VALENCY AND SIM-CII'IC HI-AT <>[' T[[|-: MF.TALS ('><)!) 



As in the series of the alkali metals we saw the metals p 

 rubidium, and caesium approaching near to each other in their proper- 

 ties, and besides them two metals having smaller combining weights - 

 namely, sodium, and the lightest of all, lithium, which already exhibited 

 < rrtain particular characteristic properties so also in the case of the 

 metals of the alkaline earths we find, besides calcium, barium, and 

 strontium, the metal magnesium and also beryllium or ylucinum. In 

 respect to the magnitude of its atomic weight, it occupies the saim- 

 position in the series of the metals of the alkaline earths as lithium does 

 in the series of the alkali metals, because the combining weight of 

 beryllium, Be or Gl=9. This combining weight is greater than the com- 

 bining weight of lithium (7), as the combining weight of magnesium (24) 

 is greater than that of sodium (23), or of calcium (40) is greater than 

 that of potassium (39), &c. 59 Beryllium was so named because it occurs 

 in the mineral beryl. The metal is also called glucinum (from the 

 Greek word yXvKvs, ' sweet '), because its salts have a sweet taste. It 

 occurs in beryl, aquamarine, the emerald, and other minerals, which 

 are generally of a green colour, and sometimes occur in considerable 

 masses, but which are as a rule comparatively rare and, as trans- 

 parent crystals, form precious stones. The composition of beryl, the 

 emerald, and smaragd is as follows : Al 2 O 3 ,3BeO,6SiO. 2 . The Siberian 

 and Brazilian beryls are the best known. The sp. gr. of beryl is 

 about 2*7. Beryllium oxide, from the feebleness of its basic properties, 

 presents an analogy to aluminium oxide in the same degree as lithium 

 oxide is analogous to magnesium oxide. 60 Owing to its rare occur- 



59 \Ve refer beryllium to the class of the bivalent metals of the alkaline earths that 

 is, we ascribe to its oxide the formula BeO, and do not count it as trivalent (Be = 13T>, 

 p. 318), as has been proposed and argued by many. The true atomic composition of beryl- 

 lium oxide was first given by the Russian chemist, Avdeeff (1819), in his researches on the 

 compounds of this metal. He compared the compounds of beryllium to those of magne- 

 sium, and set aside the then reigning opinion of the resemblance between the oxides of 

 beryllium and aluminium, by proving that beryllium sulphate presents a greater rest in 

 blance to magnesium sulphate than to aluminium sulphate. It was especially noticed 

 that the analogues of alumina give alums, whilst beryllium oxide, although it is a feeble 

 base, easily giving, like magnesia, basic and double salts, does not form true alums. The 

 establishment of the periodic system of the elements (1869), which is considered in the 

 following chapter, immediately showed that Avdeeffs view corresponded with the truth 

 that is, that beryllium is bivalent, and therefore necessitated the refutation of the 

 trivalency of beryllium. This scientific controversy resulted in a vast series of re- 

 searches (1870-80) concerning this element, and ended in Nilson and Pettersson two 

 of the chief advocates of the trivalency of beryllium determining the vapour density 

 of BeCl 2 ( 40, p. 818), which gave an undoubted proof of the bivalency of beryllium. 



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

 by alkalis as a gelatinous hydroxide BeHoO 2 , which, like alnmiua, 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 wlieii the alkaline solution is diluted 

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



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