Magnesium Oxide R1

Magnesium Oxide R1 MgO = 40.31

Use a grade of commerce that complies with the following tests.

Arsenic Dissolve 0.5 g in a mixture of 5 mL of water and 5 mL of 7m hydrochloric acid. The resulting solution complies with the limit test for arsenic, Appendix VII (2 ppm).

Heavy metals Dissolve 0.75 g in a mixture of 3 mL of water and 7 mL of 7m hydrochloric acid. Add 0.05 mL of phenolphthalein solution and sufficient 13.5m ammonia to produce a pink colour. Neutralise the excess ammonia by adding glacial acetic acid, add 0.5 mL in excess, dilute to 15 mL with water and filter if necessary. 12 mL of the solution complies with limit test A for heavy metals, Appendix VII (10 ppm). Use a mixture of 5 mL of lead standard solution (1 ppm Pb) and 5 mL of water to prepare the standard.

Iron Dissolve 0.2 g in 6 mL of 2m hydrochloric acid and dilute to 10 mL with water. The resulting solution complies with the limit test for iron, Appendix VII (50 ppm).