The alloys of gold with copper have a reddish tinge; those of gold with silver are whiter, and an alloy of gold, silver, and copper together is distinguished by a greenish tone. Manufacturers of gold ware make use of these different colors, one piece being frequently composed of several pieces of varying color. Below are given some of these alloys, with their colors:

Nos. I, II, III, and IV are green gold; No. V is pale yellow, Nos. VI, VII, and VIII bright yellow; Nos. IX and X pale red; Nos. XI and XII bright red; Nos. XIII, XIV, and XV gray; while No. X VI exhibits a bluish tint. The finished gold ware, before being put upon the market, is subjected to a special treatment, consisting either in the simple pickling or in the so-called coloring, which operation is conducted especially with alloys of low degree of fineness, the object being to give the layers a superficial layer of pure gold.

The presence of silver considerably modifies the color of gold, and the jeweler makes use of this property to obtain alloys of various shades. The following proportions are to be observed, viz.:

Gold Silver Copper Color of Gold         per per per

1,000 1,000 1,000

I.   Green......... 750    250     ...

II.  Dead leaves.. .. 700    300     ...

III.   Sea green....... 600    400     ...

IV.   Pink.......... 750    200      50

V.   English yellow.. 750    125     125

VI. English white. .. 750 150 100

VII. Whiter......... 750 170 80

VIII. Less white...... 750 190 60

IX.   Red........... 750 ... 250

Other colored gold alloys are the following:

X. Blue

Fine gold, 75; iron, 25.

XI. Dark Gray

Fine gold, 94; iron, 6.

XII. Pale Gray

Fine gold, 191; iron, 9.

XIII. Cassel Yellow

Fine gold, 75; fine silver, 12.5; rose copper, 12.5.

The above figures are understood to be by weight.

The gold solders, known in France under the names of soudures au quart (13.5 carat), au tiers (12 carat), and au deux (9 carat), are composed of 3, 2, or 1 part of gold respectively, with 1 part of an alloy consisting of two-thirds silver and one-third copper. Gold also forms with aluminum a series of alloys of greatly varying coloration, the most curious of them, composed of 22 parts of aluminum for 88 parts of gold, possessing a pretty purple shade. But all these alloys, of a highly crystalline base, are very brittle and cannot be worked, for which reason their handsome colorings have not yet been capable of being utilized.