It has extremely small amounts of calcium, iron, phosphorus, zinc, selenium and magnesium. Excess iodine can be more cytotoxic in the presence of selenium deficiency. Such elements include boron, silicon, germanium, antimony, selenium, and tellurium. Such compounds can form in mixtures of sulfur dichloride and selenium halides. It is also a good source of selenium and vitamin B12. Binary compounds with sulfur, selenium, and tellurium also exist. There is some tentative evidence for foods containing lycopene and selenium. Evidence for supplementation with selenium is mixed with some tentative evidence of benefit. The analogous sesquichalcogenides with sulfur, selenium, and tellurium are also known. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. These are formed by oxidizing mixtures of tellurium and selenium with or . The greatest purity metalorganics of both selenium and tellurium are used in these processes. Before the development of silicon power rectifier diodes, cuprous oxide and later selenium was used. It is composed of selenium and rhodium nitrates. During electrolysis precious metals like gold, silver, platinum, selenium, palladium etc.