Iron(II,III) oxide is the chemical compound with formula Fe3O4. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide (Fe2O3) which also occurs naturally as the mineral hematite. It contains both Fe2+ and Fe3+ ions and is sometimes formulated as FeO ∙ Fe2O3. This iron oxide is encountered in the laboratory as a black powder. It exhibits permanent magnetism and is ferrimagnetic, but is sometimes incorrectly described as ferromagnetic. Its most extensive use is as a black pigment. For this purpose, it is synthesized rather than being extracted from the naturally occurring mineral as the particle size and shape can be varied by the method of production. Preparation
Heated iron metal interacts with steam to form iron oxide and hydrogen gas.
Hypouricemia or hypouricaemia is a level of uric acid in blood serum that is below normal. In humans, the normal range of this blood component has a lower threshold set variously in the range of 2 mg/dL to 4 mg/dL, while the upper threshold is 530 μmol/L (6 mg/dL) for women and 619 μmol/L (7 mg/dL) for men. Hypouricemia usually is benign and sometimes is a sign of a medical condition. Presentation
Complications
Although normally benign, idiopathic renal hypouricemia may increase the risk of exercise-induced acute kidney failure. There is also evidence that hypouricemia can worsen conditions such as rheumatoid arthritis, especially when combined with low Vitamin C uptake, due to free radical damage. Causes
Hypouricemia is not a medical condition itself (i.e., it is benign), but it is a useful medical sign. Usually hypouricemia is due to drugs and toxic agents, sometimes it is due to diet or genetics, and rarely it is due to an underlying medical condition. When one of these causal medical conditions is present, hypouricemia is a common sign. Medication
The majority of drugs that contribute to hypouricemia are uricosurics (drugs that increase the excretion of uric acid from the blood into the urine). Others include drugs that reduce the production of uric acid:  xanthine oxidase inhibitors, urate oxidase (rasburicase), and sevelamer. Diet
Hypouricemia is common in vegetarians due to the low purine content of most vegetarian diets. Vegetarian diet has been found to result in mean serum uric acid values as low as 239 μ mol/L (2.7 mg/dL).