PROFESSOR J. W. MALLET ON THE ATOMIC WEIGHT OF GOLD. 
435 
The quantities of metal used being small, the centre of gravity of the balance beam 
was so adjusted as to give great sensitiveness. In calculating the weight of the 
hydrogen from its volume, the same value for the weight of a litre of the gas was 
assumed as has been already stated, viz., '08979 grin., being the result of Regnault’s 
determinations, with the correction pointed out by Loi'd Rayleigh and numerically 
estimated by Crafts, and further corrected for the force of gravity at the University 
of Virginia. 
The haloid salts of gold were prepared as for the experiments of the first and 
second series, and the careful filtration of their solutions was followed by long con¬ 
tinued standing at rest before the portions required were gently drawn off for use. 
Great care was taken in removing the last traces of precipitated gold from the bulb— 
to facilitate which the connected tubes were all cut off short—-and in repeatedly 
washing the metal, first with dilute sulphuric acid, then with pure hydrochloric acid, 
and, finally, with water, before drying, heating (in the Sprengel vacuum), cooling, and 
weip'hino-. 
The results obtained by this method were much freer from irregularity, and much 
more satisfactory, than those of the electrolytic experiments. All are reported, except 
one or two cases obviously vitiated by mechanical defects of manipulation, and, in 
consequence, not carried out to the end. 
Experiments ivith Zinc alone. 
Experiment. 
Zinc dissolved. 
Hydrogen 
obtained, at 
0° C. and 76u mm. 
i Equivalent ) 
i 1 
Hydrogen, at 0° C. 
and 760 mm., 
for 1 grm. of zinc. 
I. 
II. 
Ill. 
TV. 
grm. 
2-6990 
2-6771 
2‘70‘29 
2-7117 
c.cm. 
922-64 
915-33 
924-20 
927-51 
c.cm. 
341-85 
341-91 
341- 93 
342- 04 
Or a total amount of 10‘7907 grin, of zinc gave 3689'68 c.cm. of gas,* equivalent to 
341'93 c.cm. of hydrogen for 1 grm. of zinc. This value was adopted in calculating 
the fifth column of the following table. 
* These figures represent an atomic weight for zinc = 65'142, taking the weight of a litre of hydrogen 
at O'’ C. and 760 mm. as ‘08079 grm., and assuming the zinc used to have been absolutely pure, and the 
quantity of hydrogen collected to have been strictly equivalent to it; neither of the two latter assump¬ 
tions is essential to the use made in this paper of the experiments. Reynolds and Ramsay in their 
recent paper (‘ Chem. Soc. Journ.,’ Dec., 1887, p. 854) on the atomic weight of zinc arrive at a somewhat 
higher value, on the basis of a like comparison of the weight of the metal with the volume of hydrogen 
liberated by it, but they assume the weight of the litre of hydrogen under normal temperature and 
pressure as ‘0896 grm., which must be considered too low in view of the recently applied correction of 
Lord Rayleigh. 
3 K 2 
