Early wheels were simple wooden disks with a hole for the axle. In the early Roman empire, most horse-carts used a design featuring two chords across the wheel. The spoked wheel was invented much more recently, and allowed the construction of lighter and swifter vehicles.
Chromium(III) sulfide. Chromium(III) Sulfide is the inorganic compound with the formula Cr2S3. It is a brown-black solid. Chromium sulfides are usually nonstoichiometric compounds, with formulas ranging from CrS to Cr0.67S (corresponding to Cr2S3). Preparation.
In medicine, as a dietary supplement or slimming aid, usually as chromium(III) chloride, chromium(III) picolinate, chromium(III) polynicotinate or as an amino acid chelate, such as chromium(III) D-phenylalanine.[3] Chromium hexacarbonyl (Cr(CO)6) is used as a gasoline additive. Chromium boride (CrB) is used as a high-temperature electrical conductor. Chromium(III) sulfate (Cr2(SO4)3) is used as a green pigment in paints, in ceramic, varnishes and inks as well as in chrome plating. Chromium(VI) is used in the post Ballard preparation of Gravure (rotogravure) printing Forme Cylinders.