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XIII. Revision of the Atomic Weight of Gold. 
By J. W. Mallet, F.R.S., Professor of Chemistry in the University of Virginia. 
Received April 15,—Read May 9, 1889. 
Until lately gold ranked among the elementary substances of which the general 
properties had been well ascertained, but in regard to the atomic weights of which 
our knowledge was least satisfactory. That this constant should be determined as 
accurately as possible for gold was desii'able in view of its bearing on the precise place 
assigned the metal in the “ periodic ” classification of the elements based on the ideas 
of Newlands, Odling, Mendelejefp, and L. Meyer. Furthermore, an exact know¬ 
ledge of the atomic weight of gold might be conveniently applied in the determination 
of the atomic weights of some of the other elements. A practical laboratory reason for 
desiring to possess a trustworthy value for this constant was also presented by the 
facility with which gold compounds of many organic substances may be prepared, and 
the ease with which their composition may be ascertained by simple ignition in the 
air and weighing of the residual gold, the results leading to a knowledge of molecular 
composition when the atomic value of the weight of the metal obtained is assumed to 
be known. 
For the last three years and a half I have been occupied, during a large part of 
such time as has been available for original work, in devising and carrying out 
experiments aiming at the redetermination of the constant in question. The diffi¬ 
culties met with have been greater than were at first looked for, and have led to 
much time and labour being consumed in attempts to overcome them. About two 
years ago, when this work was already well under way but still in jirogress, there 
appeared the results of experiments aiming at the same end, by Kruss in Germany 
and by Thorpe and Laurie in England—expeiiments made with the care and accu¬ 
racy of modern methods, and apparently deserving of much confidence. My own 
work, however, was continued, as we cannot have too many careful independent 
determinations of atomic weights by different workers, and as I had used to a con¬ 
siderable extent other procesess than those on which the newly published determina¬ 
tions were based, while the chemists named had employed, in the main, one and the 
same method. A preliminary notice of my work was read in the Chemical Section of 
the British Association at the Manchester meeting of 1887. The details of my 
experiments and the results which I have reached are now laid before the Boyal 
Society. 
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