High School Chemistry . inc. 3 (a). Vary this experiment by using a piece of mag-nesium instead of zinc. Explanation.—Such chemical actions as those be-tween sodium or potassium and water, zinc and sulphuricacid, magnesium and sulphuric acid, come under theclass of substitutions in which one or more of theatoms of a molecule, generally the hydrogen, are dis-placed by atoms of other elements. 4. Take a wide-mouthed flask and fit it with a goodcork perforated by two glass tubes, one of which passesnearly to the bottom of the bottle, and has on its upperend a funnel-like expansion ; the other tub
High School Chemistry . inc. 3 (a). Vary this experiment by using a piece of mag-nesium instead of zinc. Explanation.—Such chemical actions as those be-tween sodium or potassium and water, zinc and sulphuricacid, magnesium and sulphuric acid, come under theclass of substitutions in which one or more of theatoms of a molecule, generally the hydrogen, are dis-placed by atoms of other elements. 4. Take a wide-mouthed flask and fit it with a goodcork perforated by two glass tubes, one of which passesnearly to the bottom of the bottle, and has on its upperend a funnel-like expansion ; the other tube merelypasses through thecork, is bent at rightangles, and has a rub-ber tube attached to itfor conveying the gas toa pneumatic trough,as in Fig. 7. Placesome clippings of zinc(or better, some granu-lated zinc, prepared by melting common sheet zinc inan iron ladle, then pouring it from a height of 3 or 4feet into a pail of cold water), in the bottle, fill it aboutone-third full of water, and then pour down the funnel. Fio. 7. 26 HYDROGEN. tube about one-tenth as much sulphuric acid. The gasbegins to form quickly, and is collected in bottles pre-viously filled with water and kept mouth downwards inthe water in the pneumatic trough. Collect two or threebottles or large test-tubes full of gas and preserve themfor future experiments. Preserve the liquid which re-mains in the bottle after the gas has ceased to come this liquid and either evaporate it over a lampflame, or allow it to stand in an open vessel for a day ortw*^o. Then examine carefully. 5. Keep the mouth of one of the bottles downward,and plunge a lighted taper upward into it. Then with-draw the taper slowly, allowing the burnt end to remain amoment or two at the mouth. Note exactly what phe-nomena occur (i) just as the taper enters the tube,(2) when the taper is inside the tube, and (3) just as it iswithdrawn. 6. Take the second jar, and quickly turn its mouthupwards under the mouth of a similar jar filled
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