OF MKTALS CONSII>I:KI:I> IN UKI.ATION TO TIII-: I-KRIODIC LAW. 345 



The results are also graphically represented in the accompanying diagrams (Plate 18, 

 Nos. I. and II. The tests were made with great care by Dr. E. J. BALL, Assistant in 

 the Metallurgical Laboratory of the Royal School of Mines. 



It will be evident, from the figures given in the Table, that certain mechanical 

 properties of gold are greatly affected by the addition, in small quantities, of 

 potassium, bismuth, tellurium, and lead, while other metals, such for instance as 

 silver and palladium, hardly produce an alteration. The change in the structure of 

 the precious metal is, in some cases, very remarkable, as drawings submitted to the 

 Society showed. Pure gold has a silky fracture, while gold containing the f^th 

 part of lead, tellurium, bismuth, or antimony shows a well-developed crystalline 

 structure, the crystalline planes diverging from a line in the centre of the fractured 

 bar. The character of the fracture does not appear to be closely, related to that of 

 the added metal, as lead, thallium, and indium, which produce marked crystalline 

 structure in gold, are, amongst metals, almost colloidal when pure. In these cases, 

 then, the influence exerted by the added impurity can hardly be considered to be only 

 due to a power to develop crystalline form. The question now arises, does this power 

 to produce fragility correspond with any other property of metals in accordance with 

 which they may be classified ? 



The facts represented in the Periodic Law were, in 1879, graphically represented 

 by LOTHAR MKYER in his well-known curve of the elements. By adopting atomic 

 weights as abscissze and atomic volumes as ordinates, he showed that the elements can 

 be arranged in a curve resembling a series of loops, the highest points of which are 

 occupied by caesium, rubidium, potassium, sodium, and lithium, while the metals which 

 are most useful for industrial purposes occupy the lower portions of the several loops. 



An examination of the results obtained in my experiments, so far as they have yet 

 been carried, shows that not a single metal or metalloid which occupies a position at 

 the base of either of the loops of LOTHAR MEYER'S curve diminishes the tenacity of 

 gold. On the other hand, the fact is clearly brought out that metals which do 

 render the gold fragile all occupy high positions in MEYER'S curve. This would appear 

 to show that there is some relation between the influence exerted by the metallic 

 impurities and either their atomic weights or their atomic volumes. It seems hardly 

 probable that it is due to atomic weight, because copper, with an atomic weight of 

 63'2, has nearly the same influence on the tenacity of pure gold as rhodium, with an 

 atomic weight of 104, or as aluminium, the atomic weight of which is 27. The atomic 

 volume is of course obtained by dividing the atomic weight by the specific gravity of 

 the element, and it at once becomes evident, from the tabulated results and from the 

 diagrams which graphically represent them, that the metals which diminish the tenacity 

 and extensibility of gold have high atomic volumes, while those which increase these 

 properties have either the same atomic volume as gold or a lower one. Further, 

 silver has the same atomic volume as gold, 10'2, and its presence in small quantity 

 has very little influence, one way or the other, on the tenacity or extensibility of the 

 MBOOCLXXXVITI. A. 2 Y 



