DR. T. S. HUMPIDGE ON THE ATOMIC WEIGHT OF GLUCINUM. 
613 
Making allowances for the impurities which the metal contained, the true specific 
heat (s') of the pure metal would be : — 
04316 x 100-1-32 x 0-114-4-71 x 0-247 
s =- 
93-97 
-=0-4453, 
taking the specific heat of iron as 0-114, and that of glucina as 0"247. Multiplying 
this number by the atomic weight of glucinum when its oxide is a sesquioxide, i.e., 
13-65, the atomic heat becomes 6*08, proving conclusively, if Dulong and Petit’s 
law is true for this metal as it is for all others, that this is the true atomic weight, 
and not two-thircls of this number, or 9 - l. 
The specific heat, as above determined, is considerably higher than that found by 
Nilson (0"4079), and my results might be too great for two reasons. The compressed 
metal was somewhat porous, and heat might have been produced by the absorption of 
the turpentine in its pores, and there might be a further error from hygroscopic water. 
The former supposition could be only decided by enclosing the metal in some 
impervious envelope, which has not yet been done ; the latter possible error was as far 
as practicable avoided by drying the glucinum for two hours at 150° before each 
experiment. But, even supposing the above results to be erroneous to the extent of 
10 per cent., it is still certain that the specific heat of the metal is nothing near 0'6, 
as it ought to be if the atomic weight were 9*1. 
The result is unfortunate for the periodic law, and is the first serious rebuff which 
this useful generalisation of facts has received. Glucinum, with the atomic weight of 
9"], finds its natural position as the first element of the magnesium group ; but if its 
atomic weight is 13"65, it falls between carbon and nitrogen, and entirely contradicts 
the first principles upon which the tables have been constructed. With an atomic 
weight of less than 12 it might be easily introduced, and it is possible that when 
absolutely pure such a result might be obtained. Nilson has recently made some 
determinations with the sulphate which reduced the atomic weight from the number 
previously given 13‘8 to 13"65, but it does not seem quite certain that his compounds 
were entirely free from aluminium, which would naturally increase the atomic weight. 
I hope shortly to re-determine this with the purest material it is possible to obtain. 
mdccclxxxiii. 
4 K 
