Magnesium sulfate or magnesium sulphate is a chemical compound, a salt with the formula MgSO4, consisting of magnesium cations Mg (20.19% by mass) and sulfate anions SO2−4. It is a white crystalline solid, soluble in water.
Magnesium sulfate is usually encountered in the form of a hydrate MgSO4·nH2O, for various values of n between 1 and 11. The most common is the heptahydrate MgSO4·7H2O, known as Epsom salt, which is a household chemical with many traditional uses, including bath salts.
Tofu (Japanese: 豆腐, Hepburn: Tōfu; Korean: 두부; RR: dubu, Chinese: 豆腐; pinyin: dòufu) or bean curd is a food prepared by coagulating soy milk and then pressing the resulting curds into solid white blocks of varying softness: silken, soft, firm, and extra (or super) firm. It originated in China and has been consumed for over 2,000 years. Tofu is a traditional component of many East Asian and Southeast Asian cuisines; in modern Western cooking, it is often used as a meat substitute.
Nutritionally, tofu is low in calories, while containing a relatively large amount of protein. It is a high and reliable source of iron, and can have a high calcium or magnesium content depending on the coagulants (e.g. calcium chloride, calcium sulfate, magnesium sulfate) used in manufacturing. Cultivation of tofu, as a protein-rich food source, has one of the lowest needs for land use (1.3 m/ 1000 kcal) and emits some of the lowest amount of greenhouse gas emissions (1.6 kg CO2/ 100 g protein).
Mineral springs are naturally occurring springs that produce hard water, water that contains dissolved minerals. Salts, sulfur compounds, and gases are among the substances that can be dissolved in the spring water during its passage underground. In this they are unlike sweet springs, which produce soft water with no noticeable dissolved gasses. The dissolved minerals may alter the water's taste. Mineral water obtained from mineral springs, and the precipitated salts such as Epsom salt have long been important commercial products.
Some mineral springs may contain significant amounts of harmful dissolved minerals, such as arsenic, and should not be drunk. Sulfur springs smell of rotten eggs due to hydrogen sulfide (H2S), which is hazardous and sometimes deadly. It is a gas, and it usually enters the body when it is breathed in. The quantities ingested in drinking water are much lower and are not considered likely to cause harm, but few studies on long-term, low-level exposure have been done, as of 2003.