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.
Trivalent chromium (Cr(III)) ion is possibly required in trace amounts for sugar and lipid metabolism, although the issue remains in debate. In larger amounts and in different forms, chromium can be toxic and carcinogenic.The most prominent example of toxic chromium is hexavalent chromium (Cr(VI)).aturally occurring chromium is composed of three stable isotopes; 52 Cr, 53 Cr and 54 Cr with 52 Cr being the most abundant (83.789% natural abundance). 19 radioisotopes have been characterized with the most stable being 50 Cr with a half-life of (more than) 1.8 Ã 10 years, and 51 Cr with a half-life of 27.7 days.