4. In another bottle place violets or a carnation. Result?

5. In the fourth bottle suspend a strip of moist white cloth having an ink stain. Result?

6. Into the "chlorine water" prepared in (1) place a strip of white goods having an ink stain.

7. Explain the use of bleaching powder (chlorinated lime) in removing stains and in bleaching goods, and as a disinfectant.

C. Preparation and Properties of Bromine.

1. Place 5 grams of powdered potassium bromide and 3 grams of manganese dioxide in a 250 cc. Florence flask. Add 20 cc. of 4 N sulfuric acid. Warm if necessary. Write the equation for the preparation.

2. Note the color and the odor of the bromine gas. At an ordinary temperature bromine is a liquid. It is the only liquid non-metal. Examine some liquid bromine. Pour a drop of bromine into water. Does it dissolve? Is it heavier or lighter than water?

D. Preparation and Properties of Iodine.

1. Repeat C, 1 using potassium iodide instead of potassium bromide. Write the equation for the preparation of iodine.

2. Note the color of iodine vapor. What collects upon the cold neck of the flask?

3. Examine crystals of iodine. Describe them. Put a crystal in a test tube and heat it. Result? What collects on the sides of the tube? Explain.

4. Try to dissolve a crystal of iodine in water. Result? Pour off the water and add alcohol. The solution of iodine

in alcohol is called "tincture of iodine." What is this used for?

5. To a beaker of water add 1 drop of starch paste and then 1 drop of the tincture of iodine prepared in (4). Result? This is a test for starch.

EXPERIMENT 24

Preparation and Properties of Hydrochloric Acid, HC1 MATERIALS. 30 g. portions of NaCl, 4 N sulfuric acid, litmus paper, splints, blue litmus solution, silver nitrate solution, ammonium hydroxide, nitric acid, potassium chloride.

APPARATUS. 250 cc. Florence flask, delivery tubes, gas bottles, large beaker, test tubes, thistle tube.

A. Preparation of the Gas Hydrogen Chloride.

1. Put about 30 grams of sodium chloride (common salt) into your 250 cc. Florence flask. Insert the 2-hole rubber stopper containing the thistle tube and delivery tube. Attach the long delivery tube to the short one and extend it into a dry gas bottle covered with cardboard. Add through the thistle tube about 50 cc. of sulfuric acid and warm gently. Collect 2 bottles of gas hydrogen chloride. The bottles are full when a piece of moist blue litmus paper held at the mouth turns pink. Cover them with about 50 cc. of water, forming hydrochloric acid. Write the word-andsymbol equation for the preparation of the gas hydrogen chloride.

B. Properties of the Gas Hydrogen Chloride.

1. Note the color and odor of the gas. Is it heavier than air?

2. Thrust a lighted splint into one of the bottles. Does hydrogen chloride burn? Does it support combustion?

3. Fill your large beaker with water and add 1 cc. of blue litmus solution. Uncover the second bottle of the gas and invert it quickly in the beaker of water. Explain the result. C. Properties of Hydrochloric Acid.

1. Remove the delivery tube from the bottle containing the water in which the hydrogen chloride has dissolved, forming hydrochloric acid. Test the liquid with blue litmus paper. Result? Taste a

drop of the liquid. Result?

What is the hydrochloric acid on your desk?

2. Place 5 cc. of the hydrochloric acid which you prepared in a test tube and add a drop of silver nitrate. What is the white precipitate formed? Write the word-and-symbol equation. Divide the precipitate into two parts. To one part add ammonium hydroxide till the liquid is alkaline. Result? To the other part add nitric acid. Result?

3. Repeat (2), using any soluble chloride instead of hydrochloric acid. Result? Write the equation to show the formation of silver chloride.

State the test for hydrochloric acid and its salts. What is the general method for the preparation of an acid?

VII. SULFUR AND COMPOUNDS OF SULFUR

EXPERIMENT 25

Sulfur and Compounds of Sulfur

MATERIALS. Sulfur, colored goods, a colored flower, sodium sulfite, concentrated sulfuric acid.

APPARATUS. Deflagrating spoons, gas bottle, pneumatic trough, litmus paper, flask, test tubes, safety tube, delivery tube.

A. Sulfur.

1. Note the physical properties of sulfur, i.e. color, odor, taste.

2. Boil some sulfur in a test tube half full of water. Filter and note that the water is pale yellow. Is sulfur soluble in water?

3. What are some of the uses of sulfur?

B. Sulfur Dioxide, SO2.

1. Place about 20 grams of sodium sulfite in a flask. Insert the stopper with a thistle tube and delivery tube. Add concentrated sulfuric acid through the thistle tube. Warm the flask if necessary. Collect the gas by downward displacement of air. Fill 3 bottles. Write the equation to show the reaction that takes place in this method of preparing sulfur dioxide.

Note: Sulfur dioxide can also be prepared by burning sulfur in the air. Write the equation.

2. Note the physical properties of the gas, i.e. the color and odor. Half fill your trough with water and quickly invert one bottle of sulfur dioxide in it. Is sulfur dioxide soluble in water? When the water no longer rises slip a glass plate over the mouth of the bottle and place it right side up on the table. Taste the liquid in the bottle. Test it with red and with blue litmus. What is formed when sulfur dioxide dissolves in water? Write the equation to show the reaction.

3. Into the second bottle thrust a burning splint. Does sulfur dioxide burn or support combustion?

4. Into the third bottle of sulfur dioxide place a strip of moistened colored goods and also a fresh violet or carnation

or other colored flower. This illustrates the use of sulfur dioxide as a bleaching agent for nuts and fruits before they are dried. In this case the sulfur dioxide is prepared by burning sulfur in air.

MATERIALS.

EXPERIMENT 26

Sulfuric Acid and Hydrogen Sulfide

Pine splint, concentrated sulfuric acid, sugar, sodium acetate, distilled water, barium chloride solution, hydrochloric acid, and ferrous sulfide.

APPARATUS. Test tubes, flask, delivery tube, safety tube, litmus paper, and splints.

A. Sulfuric Acid.

1. Pour 1 cc. of concentrated sulfuric acid into 5 cc. of water in a test tube. (Caution: Never pour the water into the acid.) Note the heat produced by touching the bottom of the test tube to the hand.

2. Thrust a pine splint into 5 cc. of concentrated sulfuric acid in a test tube. Warm gently. Remove the splint and note result.

3. To a gram of sugar in another test tube add a few drops of concentrated sulfuric acid. Warm and explain result. Write the equation to illustrate in a general way what took place. Explain why concentrated sulfuric acid causes such serious burns.

4. Half fill a test tube with distilled water, then add a drop of concentrated sulfuric acid. To this add 1 cc. of barium chloride solution. The precipitate is barium sulfate, BaSO4. Try to dissolve the precipitate in hydrochloric acid. Result? In nitric acid. Result? State the test in your own