CHAPTER XLVIII.

GOLD AND PLATINUM.

Au; 196.7. Pt; 194.3.

SALTS of these precious metals are official,―the gold salt as a substance in the materia medica, the platinum salt as a test-liquid: both are chlorides. Gold and platinum are both found native in the free state. Latin names for these metals are Aurum and Platinum.

Tests for Gold Salts.

1. If hydrogen sulphide be added to the solution of a gold salt, a dark brown, almost black, precipitate (auric sulphide) will be produced, soluble in ammonium sulphide.

2. If ferrous sulphate be added to a solution of a gold salt, metallic gold in the form of a fine precipitate will be produced: this may be fused into a button of gold by the use of the blow-pipe.

3. Stannous chloride if added to dilute solutions of gold salts produces a purple precipitate (purple of Cassius).

Tests for Platinum Salts.

1. If hydrogen sulphide or ammonium sulphide be added to a solution of platinic chloride, a brown precipitate of platinic sulphide will be produced, soluble in excess of ammonium sulphide.

2. If a solution of potassium chloride be added to a solution of platinic chloride acidulated with hydrochloric acid, a yellow precipitate (double chloride) will be formed.

Official Name.

Official Salts of Gold and Platinum.

Preparation.

Auri et Sodii Chloridum. . Equal parts of dry auric chloride and sodium chloride.
Platini Chloridum
Test-solution of platinic chloride, 1 part of platinic chlo-
ride in 20 parts of distilled water.

Auri Bromidum, AuBrs.
Gold Bromide.

Auri Chloridum, AuCl3.
Gold Chloride.

Auri Iodidum, AuIs.
Gold Iodide.

Unofficial Preparations of Gold.

By dissolving gold in a mixture of nitric and hydrobromic acids, concentrating, then crystallizing.

By dissolving gold in nitrohydrochloric acid, concentrating carefully, then crystallizing.

By gradually adding a neutral solution of auric chloride to a solution of potassium iodide, then collecting and drying the precipitate.

AURI ET SODII CHLORIDUM. U.S. Gold and Sodium Chloride.

A mixture of equal parts, by weight, of dry Gold Chloride [AuCl2 = 302.81] and Sodium Chloride [NaCl = 58.37].

Preparation. It may be made by dissolving gold in nitrohydrochloric acid, evaporating the solution to dryness, weighing, and dissolving the dry mass in eight times its weight of distilled water. To this solution a weight of pure decrepitated common salt equalling that of the dry gold chloride is added, previously dissolved in four parts of water. The mixed solution is then evaporated to dryness, being constantly stirred with a glass rod.

If 0.5 Gm. of Gold and Sodium Chloride be
dissolved in 50 C.c. of water, in a porce-
lain capsule, the solution acidulated with Free Acid.
5 C.c. of dilute sulphuric acid, and, after
the addition of 1 Gm. of pure oxalic acid,
heated for about 2 hours, on a water-bath,
a precipitate of metallic gold will be ob
tained, which, when washed, dried, and
ignited, should weigh not less than 0.15
Gm. (corresponding to at least 30 per cent.
of metallic gold).

Metallic Im-
purities.

TESTS FOR IMPURITIES.

On bringing a glass rod dipped
into ammonia water close to
a portion of the compound,
no white fumes should make
their appearance.
The filtrate from the precipi-
tated gold should not be af-
fected by hydrogen sulphide
T.S., nor, after being super-
saturated with ammonia water,
by ammonium sulphide T.S.

Uses. This salt is used internally as an alterative. The dose is from one-twelfth to one-fourth of a grain (0.006 to 0.016 Gm.).

QUESTIONS ON CHAPTER XLVIII.

GOLD AND PLATINUM.

Gold-What is the Latin name? Give the symbol and atomic weight.
In what form is it official? How is it found?

What are the tests for gold salts?

Platinum-Give the symbol and atomic weight.

What salt of it is official, and for what is it used? How is it found?
What are the tests for platinum salts?

Gold and sodium chloride-What is the composition of this salt?

Give the formulas and equivalents of each of the ingredients.

How is it made?

Describe odor, taste, chemical reaction, and solubility. Give tests for identity.
How may its quality be tested? How may free acid be detected?
What is the dose?