CARBON.

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EXPERIMENT XLV.

CARBON.

Apparatus. Tongs, test tubes, iron dish with a cover, beaker.

Materials. Charcoal (lumps and powder), graphite (pencil lead), soft coal, hydrogen sulphide solution, litmus solution, brown sugar, animal charcoal.

a. Hold a piece of charcoal in the Bunsen flame (use tongs) and describe its combustion. Repeat with graphite (pencil lead) and with soft coal.

b. Fill an old test tube one-fourth full of bits of wood, and heat. Results? Bring a burning match to the mouth of the tube. Result? Describe the other products. What is the residue?

c. Hold a piece of wood charcoal under water in a beaker for two minutes. What appears on its surface? Conclusion?

d. Heat powdered wood charcoal or animal charcoal for five minutes in a covered iron dish. Let it cool, and add 2 c.c. of it to 5 c.c. hydrogen sulphide solution. Shake thoroughly and filter. Compare odor of filtrate with that of the solution taken. Conclusion?

e. Boil 5 c.c. litmus solution two minutes with 2 c.c. of the freshly ignited charcoal, and filter. Result? Repeat, using 5 c.c. of a solution of brown sugar with 2 c.c. fresh charcoal. Result?

EXPERIMENT XLVI.

CARBON DIOXIDE, I.

Apparatus. Generating bottle, stopper with thistle tube and delivery tube, pneumatic trough, beaker, test tubes, and collecting bottles.

Materials. Marble, hydrochloric acid, litmus, lime-water.

a. Place in a bottle enough marble (a form of calcium carbonate, CaCO3) to cover the bottom, add enough water to close lower end of the thistle tube, insert stopper, and add concentrated hydrochloric acid through the thistle tube. Add more acid when it is needed. Collect the carbon dioxide (CO2) over water, rejecting the first bottle of the gas. See, also, Experiment XX.

b. Put into a bottle of the gas wet litmus paper (red and blue) and a burning match. Results?

c. Pour a bottle of the gas into a beaker of air. Test the gas in the beaker with a burning match. Result? Conclusion as to the specific gravity of the gas?

d. Fill a test tube with the gas by air displacement, add 5 c.c. cold water, close tube securely with thumb, shake vigorously, and open under water. Result? Conclusion?

e. Pass the gas into lime-water, Ca(OH)2. Result? Let the precipitate settle. It is calcium carbonate. Its formation with lime-water is a test for carbon dioxide (cf. Experiment V, e). Now pass a vigorous stream of the gas into the tube five minutes. Result? Boil the contents of the tube. Result?

EFFECT OF HEAT ON CARBONATES.

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Apparatus.

EXPERIMENT XLVII.

CARBON DIOXIDE, II.

Beakers, delivery tube, test tubes.

Materials. Lime-water, sodium bicarbonate, tartaric acid.

a. Mix 2 c.c. each of sodium bicarbonate (NaHCO3) and tartaric acid (H2C4H4O6) in a mortar. Is a change apparent? Put half of the powder into a test tube, and add water. Result? Identify the gas.

b. Put the remainder of the mixture from a in a test tube, add 10 c.c. water, and, as soon as you are able, imprison the gas by holding your thumb upon the mouth of the test tube. Effect upon the effervescence? Now remove your thumb. Effect? Explain.

c. Blow your breath through a delivery tube into 5 c.c. lime-water. Result? Conclusion?

d. Expose 5 c.c. clear lime-water to the air for several hours. Result? How does carbon dioxide get into the air (cf. Experiment V, e)?

EXPERIMENT XLVIII.

REDUCTION BY CARBON. EFFECT OF HEAT ON

CARBONATES.

Apparatus. Ignition tube, delivery tube, rubber connector, test tubes.

Materials. Lead monoxide, powdered charcoal, lime-water, magnesite.

a. Mix 1 c.c. lead monoxide, PbO, with one-third its volume of powdered charcoal, on smooth paper. Into the ignition tube put enough of the mixture to make a layer 1 cm. thick, support the tube almost horizontally, and attach a delivery tube leading into 5 c.c. lime-water. Heat the lead monoxide persistently for ten minutes, cool it, and pour it out on the table. Result? What gas was evolved? Write the equation.

b. Fill the ignition tube one-fifth full of chips of magnesite, MgCO3, and set it up as in a. Heat persistently. What gas is evolved? What, then, does the residue contain? Write the equation.

Apparatus.
Materials.

EXPERIMENT XLIX.

FLAMES.

Bunsen burner and tongs.

Candle, piece of porcelain, white paper.

a. Examine carefully the non-luminous flame.

Sketch

a vertical section of it as you see it. Make drawing 4 cm. long.

b. Do the same with a luminous Bunsen flame 2 cm. high. Repeat with a candle flame.

c. Press the colorless Bunsen flame for a moment upon paper lying on your table. The paper should not burn up. Result?

Hold a piece of glass tubing about 1 dm. long at an angle of forty-five degrees, with the lower end inside the central part of the non-luminous flame, and apply a lighted

match to the other end. Result? What do these experiments show as to the inner region of the flame?

d. Hold a piece of porcelain (broken evaporating dish) by means of tongs in the luminous flame. Result? What substance is in excess here? Now hold the porcelain in the colorless flame for some time. Result? What is in excess in this flame?

Apparatus.

EXPERIMENT L.

BROMINE.

Beaker, 100 c.c. flask, test tubes.

Materials. Potassium bromide, powdered manganese dioxide, dilute sulphuric acid, litmus paper, calico, carbon disulphide, chlorine-water, sodium hydroxide.

Caution. If possible, work in a gas-chamber or hood.

a. Into a flask put an eighth of a test tube of potassium bromide (KBr) crystals, half as much powdered manganese dioxide, and half a test tube of dilute sulphuric acid. Support the flask over wire gauze, and attach the cork stopper and a doubly bent delivery tube reaching into a test tube three-fourths full of cold water. The delivery tube must be without rubber connections. The test tube should rest in a beaker of water (cf. Experiment XI).

b. Warm the flask carefully until a dark brown distillate passes over. Is it heavier or lighter than water? Do not inhale the vapor, and do not get liquid bromine on your hands.