Why "cadmium" is yellow?

Stromeyer discovered metallic cadmium in 1817 but production of the cadmium pigments was delayed until about 1840 because of the scarcity of the metal. A natural mineral, green ochite, is known in nature but was not used for pigments. Cadmium sulfide was prepared with an acid solution of cadmium salt (either chloride or sulfate) which was heated with hydrogen sulfide gas until a powder was formed. Hues ranging from a lemon yellow to a deep orange were made in this way. The deeper varieties of cadmium yellow and orange were the most permanent. The paler varieties were known to fade on exposure to sunlight. All of the cadmiums were brilliant and the deeper shades had the greatest tinting strength. Field claimed that the best cadmiums were those produced without an excess of sulfur and that the permanence of a carefully made cadmium was improved when mixed with lead white using only an ivory knife. They were used in both oil and watercolor but could not be mixed with copper-based pigment.

Why "cobalt" is blue?

Cobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts. The world leading manufacturer of cobalt blue in the 19th century was Blaafarveværket in Norway, led by Benjamin Wegner. The pigment is extraordinarily stable. Chemically it is a cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl₂O₄. The compound is made by sintering the stoichiometric mixture of finely ground CoO and Al₂O₃ at 1200°C. It was discovered by Louis Jacques Thénard in 1802^. Commercial production began in France in 1807. The first recorded use of cobalt blue as a color name in English was in 1777. John Varley suggested cobalt blue as a good substitution for ultramarine blue for painting skies. Maxfield Parrish, famous partly for the intensity of his skyscapes, used cobalt blue, and cobalt blue is sometimes called Parrish blue as a result. Because of its chemical stability in the presence of alkali, cobalt blue is used as a pigment in blue concrete. The blue seen on many glassware pieces is cobalt blue, and it is used widely by artists in many other fields. "Cobalt Blue" is used as a filter used in ophthalmoscopes, and is used to illuminate the cornea of the eye following application of fluorescein dye which is used to detect corneal ulcers and scratches. Major League Soccer's Kansas City Wizards have had cobalt blue as the primary color of its home uniforms since 2008.

Taukah teman??"emas" terkandung di air laut lho....

Emas ditemukan di deposit-deposit veins dan alluvial dan seringnya dipisahkan dari bebatuan dan mineral-mineral lainnya dengan proses penambangan dan panning. Sekitar dua pertiga produksi emas dunia berasal dari Afrika Selatan dan sekitar dua pertiga produksi total Amerika Serikat datang dari negara bagian South Dakota dan Nevada. Logam ini diambil dari bijih-bijihnya dengan berbagai cara: cynaniding, amalgamating, dan smelting. Proses pemurnian juga kerap dilakukan dengan cara elektrolisis. Emas terkandung pula di air laut sekitar 0.1 sampai 2 mg/ton, tergantung dimana sampel air lautnya diambil. Sampai sekarang, belum ditemukan bagaimana cara menambang emas dari air laut yang dapat memberikan untung.Dari beberapa sumber yang dapat dipercaya, diketahui bahwa pengeboran minyak dan gas bumi lepas pantai, memberikan kontribusi sekitar 25 hingga 30% dari total produksi minyak dan gas dunia. Bahan tambang dan mineral lain yang dapat ditemukan didaerah pesisir dan laut, diantaranya: mutiara, pasir, gravel, mas, polimetalik sulfat dan hidro-karbon.