Note 29 — Chapter XXIV · COPPER, SILVER, AND GOLD

Heavy atoms and molecules, although they may present many points of analogy, are more easily isolated; thus C16H32, although, like C2H4, it combines with Br2, and has a similar composition, yet reacts with much greater difficulty than C2H4, and in this it resembles gold; the heavy atoms and molecules are, so to say, inert, and already saturated by themselves. Gold in its higher grade of oxidation, Au2O3, presents feeble basic properties and weakly-developed acid properties, so that this oxide of gold, Au2O3, may be referred to the class of feeble acid oxides, like platinic oxide. This is not the case in the highest known oxides of copper and silver. But in the lower grade of oxidation, aurous oxide, Au2O, gold, like silver and copper, presents basic properties, although they are not very pronounced. In this respect it stands very close in its properties, although not in its types of combination (AuX and AuX3), to platinum (PtX2 and PtX4) and its analogues.

As yet the general chemical characteristics of gold and its compounds have not been fully investigated. This is partly due to the fact that very few researches have been undertaken on the compounds of this metal, owing to its inaccessibility for working in large quantities. As the atomic weight of gold is high (Au = 197), the preparation of its compounds requires that it should be taken in large quantities, which forms an obstacle to its being fully studied. Hence the facts concerning the history of this metal are rarely distinguished by that exactitude with which many facts have been established concerning other elements more accessible, and long known in use.