words. Complete the following equations, naming all sub 1. Set up your flask as a gas generator. In it place 10 grams of ferrous sulfide. Add hydrochloric acid through the safety tube. Collect a bottle of the gas by downward displacement of air. Complete the following equation for the reaction, naming all substances: FeS+2 HCI 2. Note the physical properties of the gas, i.e. color, odor. Note: Let the gas bubble into a test tube of water while you are studying the properties of the gas in the bottle. 3. Thrust a burning splint into the bottle of gas collected. Result? The hydrogen sulfide is oxidized to water and sulfur dioxide when it burns. Write the equation for the reaction which takes place when hydrogen sulfide burns in the air. 2 H2S+3 02 Sometimes sulfur is precipitated if the oxidation is incomplete. Write an equation to illustrate this reaction. 2 H2S+02 Hydrogen sulfide is a strong reducing agent. 4. Test the solution of hydrogen sulfide prepared in (2) with red and with blue litmus. Result? It is a very weak acid. Put a drop of the solution on a silver coin. Result? Why do silver spoons turn black if used for eating eggs? 5. How would you test for a sulfide? VIII. CARBON. CARBON DIOXIDE. FLAMES MATERIALS. EXPERIMENT 27 Carbon Potato, bread, meat, starch, sugar, cotton, paper, wood, coal, any vegetable, sand, wood charcoal, lampblack, bone black, graphite, coal, sulfuric acid, sodium hydroxide, brown sugar, copper oxide. APPARATUS. Iron pan, ring stand, test tubes, filter paper, funnel, beaker, hard-glass test tube. A. Occurrence of Carbon. 1. Place a thin layer of sand in a small iron pan and on it put small pieces of the substances listed above. Cover the materials with sand to protect from the action of the air. Why? Heat until smoking ceases. Cool and examine. What has happened to the substances? What is the black residue ? How is willow charcoal prepared? How is animal charcoal prepared? For what purposes are these substances used? 2. Close the holes in the Bunsen burner; light it and turn it low. This makes a small luminous flame. Hold a cold, dry surface or evaporating dish in this flame. Result? What is this form of carbon called? How is lampblack prepared? For what purpose is it used? What element is found in the foods we eat and the fuels we burn? B. Properties of Carbon. 1. In five different test tubes place respectively about 5 grams of wood charcoal, bone black (animal charcoal), graphite, lampblack, coal. Note the physical properties of each. Place small portions of each in other test tubes and add some water. Are any of the forms of carbon soluble in water? 2. Place portions of each in other tubes and add some sulfuric acid or any acid. Result? Repeat, using sodium hydroxide. Result? 3. Dissolve 20 grams of brown sugar in 100 cc. of water. Note the color of the solution. Add 10 grams of bone black and boil for ten minutes. Filter. Note the color of the filtrate. Taste it. Where is the sugar? If the filtrate is not colorless, add some more bone black; warm and filter again till it is colorless. How is bone black used in sugar refining? 4. In a hard-glass test tube heat for 10 minutes a mixture of 3 grams of powdered wood charcoal with 3 grams of copper oxide. Cool and pour the contents upon a paper. What is the reddish material? What becomes of the charcoal? Write an equation to show the reducing action of carbon in this case. MATERIALS. water. APPARATUS. EXPERIMENT 28 Carbon Dioxide, CO2 Marble chips, dilute hydrochloric acid, splints, lime Flask, safety tube, stopper, delivery tube, bottles, beaker, test tubes. A. Preparation of Carbon Dioxide. 1. Place some pieces of marble in your 250 cc. flask. Insert the stopper containing the safety tube and the delivery tube. Add dilute hydrochloric acid through the safety tube, a few centimeters at a time. 2. Collect three bottles of the gas by downward displace ment of air. The bottle is full when the flame of a burning splint held at its mouth is extinguished. 3. Write the equation for the reaction between hydrochloric acid and marble in the preparation of carbon dioxide. B. Properties of Carbon Dioxide. 1. Note the chief physical properties of carbon dioxide. Test its solubility in water by inserting one of the bottles of the gas in a beaker of water. Let it stand. Does the water rise? Is carbon dioxide soluble in water? 2. Into a second bottle of the gas thrust a burning splint. Result? What use does this suggest for the gas? 3. Prove that the gas is heavier than air by pouring a bottle of it into an empty bottle as if it were a liquid. Test for its presence in the second bottle with the burning splint. Result? 4. Extend the delivery tube from the generator into 10 cc. of limewater in a test tube and allow the carbon dioxide to bubble through the limewater. What is the white precipitate obtained? Write the equation for the reaction. This is a test for carbon dioxide. 5. Prove that air exhaled from the lungs contains carbon dioxide by blowing some air through 10 cc. of fresh limewater in a test tube. Explain the presence of carbon dioxide in the air exhaled from the lungs. 6. Burn a splint in a bottle. Cover the bottle. Add limewater and shake. Result? Explain. 7. Burn a piece of paper in a bottle. Cover the bottle. Add limewater and shake. Result? Explain. 8. Any substance which contains carbon will form carbon dioxide when it burns. The limewater test for carbon dioxide is therefore an indirect test for carbon. Note: If there is time, perform A, 1 and B, 1 of Experiment 29. MATERIALS. EXPERIMENT 29 Carbonic Acid and Carbonates Carbon dioxide generator, sodium hydroxide, sodium bicarbonate, copper carbonate, magnesium carbonate, sodium bicarbonate, hydrochloric or sulfuric acids, limewater, baking soda, washing soda, boiler scale, sea shells, limestone. APPARATUS. Evaporating dish, test tubes. A. Carbonic Acid, H2CO3. 1. Pass some of the carbon dioxide gas from the generator used in Experiment 28 through 25 cc. of water. The gas combines with the water to form carbonic acid. Write the equation for the reaction. Taste the liquid. Result? Test the acid formed with blue litmus paper. Result? Now explain what soda water is. B. Salts of Carbonic Acid, the Carbonates. 1. Pass carbon dioxide through 20 cc. of solution of sodium hydroxide in a test tube as long as any gas is absorbed. Pour the solution into your evaporating dish and evaporate to dryness. What substance remains? Write the equation for the reaction. 2. In labeled tubes obtain 1 gram of sodium bicarbonate, copper carbonate, magnesium carbonate, and sodium carbonate. Note the physical properties of each. Place half of the sodium bicarbonate in another test tube, add 20 cc. of water, warm, and shake. Is sodium bicarbonate soluble in water? In like manner test the solubility of the other carbonates |