Прочтите текст про себя (контрольное время чтения — 5 минут). Selenium Compounds
The clement (selenium) can combinc with the metals Just as sulphur can, forming selenides. Let us grind some selenium to powder in a mortar. After that, wc should take 10 grams of this powder and grind it with 7 grams of iron dust, a proportion of 80 and 56, the approximate atomic weight ratio of the two elements. Then, wc must pour the well-mixed material into a dry test-tube and heat it. Ferrous scicnidc is formed, the action proceeds somewhat less vigorously than that between iron and sulphur. When the tube has cooled somewhat, wc can break it open and remove a grcy-black product which much resembles ferrous sulphide. Selenium will unite similarly with zinc and with other metals such as copper and lead.
Selenium dioxide may be formed by the combustion of the clement. The dioxide is white and can dissolve readily in water to form sclcnious acid just as sulphur dioxide dissolves to form sulphurous acid:
H20 + Sc02 -> H2ScOj.
When sclcnious acid is treated with chlorine or potassium permanganate, sclcnic acid is produced; the process, of course, can be called oxidation, the reaction proceeds just as it does with sulphurous acid. Small lumps of ferrous selcnidc arc transferred to a small flask connected to a train of bottles containing solutions of a number of different metallic salts, for example, those of cadmium, cobalt, nickel, arsenic, and antimony. Any excess of gas which may escape is led into the flue. Add some hydrochloric or sulphuric acid to the material in the flask, and presently hydrogen selenidc forms and bubbles into the liquids in the various bottles. Various selenides can be formed.
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