1883.] 



Atomic Weight of Glucinum or Beryllium. 



249 



attempting to prepare even a few decigrams of beryllium are so great, 

 that both sets of experiments have been objected to on the ground, 

 amongst others, that the metal employed was in all cases impure. My 

 specimen admittedly contained a minute quantity of platinum, and the 

 proportion of known impurity in one of MM. Nilson and Pettersson's 

 specimens reached 13 per cent. Unfortunately, Professor Humpidge's 

 metal, though claimed to be the purest yet prepared, is shown by 

 analysis to be rather less pure than one of the specimens employed by 

 Nilson and Pettersson, hence the experiments lately made known to 

 the Society do not carry the inquiry beyond the point previously 

 reached, save in one noteworthy particular, namely, that there appears 

 to be a considerable, though irregular, rise in specific heat of the 

 element as the proportion of impurity diminishes ; but the value 

 is still much below that required for the atomic weight 9"2. Thus for 

 a specimen of beryllium which contained 13 per cent, of known 

 impurity Mlson and Pettersson obtained the specific heat 0'4084 

 between 0° and 100° C, and for a less impure specimen 0*425 ; while 

 Professor Humpidge, in one of his experiments with a material that 

 contained 6 per cent, of impurity, found the specific heat to be nearly 

 0*45 (0'4497). In all these cases corrections were applied which were 

 believed to eliminate the effects due to the impurities known to be 

 present — in part mechanically mixed with the metal and partly alloyed 

 with it. 



These results all tend in one direction, that is to say, to apparent 

 gain in specific heat with increased purity of material, and in so far 

 they approach the still higher value obtained in my old experiments. 

 But even if the latter had not been made, the apparent rise in specific 

 heat shown by the other determinations, would suggest the necessity 

 for appeal to data afforded by beryllium of undoubted purity. In order 

 that further experiments should now be considered decisive, the metal 

 should not only be pure, but in the form of a homogeneous mass 

 obtained by fusion, as the specimen I used was an apparently 

 uncrystalline product of fusion, while the metal employed by Nilson 

 and Pettersson chiefly consisted of " aggregations of little prismatic 

 needles," mixed with the oxide. 



The most promising source of pure beryllium is the double fluoride 

 of the element and potassium, but I have not hitherto succeeded in 

 making the product of reduction form a button of metal. 



Professor Hartley has very recently made known some highly 

 interesting spectroscopic evidence* affecting the position of beryllium 

 amongst the metals, and so directly bearing on the question of its 

 valence that I may be permitted to refer to the results in this place. 



If the atomic weight of beryllium be 13*8, the element is a triad and 

 the formula of its oxide must be Be 2 3 . The latter therefore resembles 

 * In a communication read before the Chemical Society, April 19, 1883. 



