I cannot find any metallurgic, industrial, or chemical references to "white copper" being used as a term for copper-arsenic alloys. The closest I came was this section from Henley's Twentieth Century Formulas Recipes Processes by Norman W. Henley and others.

Copper Arsenic Alloys

Arsenic imparts to copper a very fine white color, and makes it very hard and brittle. Before German silver was known, these alloys were sometimes used for the manufacture of such cast articles as were not to come in contact with iron. When exposed to the air, they soon lose their whiteness and take on a brownish shade. On account of this, as well as the poisonous character of the arsenic, they are very little used at the present time. Alloys of copper and arsenic are best prepared by pressing firmly into a crucible a mixture of 70 parts of copper and 30 of arsenic (the copper to be used in the form of fine shavings) and fusing this mixture in a furnace with a good draught, under a cover of glass.

Note that such alloys start out as white, but quickly turn brown. In fact, some very early bronzes were copper-arsenic alloys instead of the copper-tin alloys that are used today. Like all bronzes, they are brown in color.