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.
Iron(II,III) sulfide. From Wikipedia, the free encyclopedia. Iron(II,III) sulfide is a blue-black (sometimes pinkish) chemical compound of iron and sulfur with formula Fe 3 S 4 or FeSÂ·Fe 2 S 3, which is much similar to iron(II,III) oxide. It occurs naturally as the sulfide mineral greigite and is magnetic.It is a bio-mineral produced by and found in magnetotactic bacteria.ike the related oxide magnetite (Fe 3 O 4), iron(II,III) sulfide is ferrimagnetic, with the spin magnetic moments of the Fe cations in the tetrahedral sites oriented in the opposite direction as those in the octahedral sites, and a net magnetization.