no longer be seen. A soap is formed. The process is called saponification. Write two equations to show the reactions that took place. Name all substances.

C. Tests for Fats and Oils.

1. The reagent Sudan III stains fats and oils. Cut open a castor bean or a sunflower seed; apply a drop of the reagent. Result? In like manner test boiled egg yolk for fat.

2. Some substances contain sufficient fat to give the 'grease spot" test. Rub a piece of walnut on a page of your scratch pad placed on the table. Is a grease spot formed? Warm the spot over the burner. It should not disappear. In this way test chocolate.

3. The fat may be extracted from the substance by mixing well with ether or gasoline. The gasoline will dissolve the fat and then if allowed to evaporate, the fat will be left.

Put about 10 grams of grated cheese in one of your beakers. Add 25 cc. of gasoline; stir well.

Caution: Have no flames near.

Filter into your beaker and allow the filtrate to evaporate. What remains in the beaker?

4. What is the use of fats to the body? From the Appendix make a list of 10 foods containing much fat (80% to 100%). Make a list of 10 foods containing very little or no fat (10% to none). Name five fats or oils of commercial value and give their uses.

NITROGENOUS SUBSTANCES

Nitrogenous substances are very complex compounds, found in some plant and nearly all animal tissues. The most important nitrogenous substances are called proteins. They are composed of carbon, hydrogen, oxygen, and about

14% of nitrogen with varying amounts of sulfur and phosphorus. The proteins may be classified into four groups: (1) Those soluble in cold water and coagulated by hot water, called the albumens (egg albumen, blood albumen, milk albumen). (2) Those soluble in hot or cold water (casein in milk). (3) Those not soluble in hot or cold water, called globulins (myosin in meat, gluten in flour, and legumen in peas and beans). (4) Those soluble in hot water but not in cold, called albuminoids or gelatinoids because when the hot solution is allowed to cool a jelly is formed (collagen from skin, cartilage, and bones, and keratin from hair, horns, and hoofs).

MATERIALS.

EXPERIMENT 43

The Albumens and Casein

Fresh egg albumen, concentrated nitric acid, ammonia, Millon's reagent, dry blood albumen, dry egg albumen, soda lime, red litmus paper, fresh milk, rennin, dilute hydrochloric acid or acetic acid.

APPARATUS. Test tubes, funnel, filter paper, evaporating dish, stirring rod.

A. The Albumens (Soluble in Cold Water, Coagulated by Hot Water). 1. Obtain 1 cc. of fresh egg albumen in a test tube. Note its physical properties. Add 20 cc. of cold water and shake well. Does it dissolve?

2. Heat the solution of egg albumen. Result?

3. Filter the coagulated albumen and place a portion of it in your evaporating dish. Heat slowly and note the peculiar odor of burning protein. Explain. This is the "burning test" for proteins.

4. To another portion of the coagulated albumen add

concentrated nitric acid till the albumen is covered. Warm gently. Result? Now pour off the acid, rinse with water, and add ammonia. Result? This is the xanthoproteic

test for proteins.

5. Obtain about 10 cc. of blood albumen in water. Add 1 cc. of Millon's reagent and boil. Result? This is Millon's test for proteins.

6. Obtain 2 grams of dry blood or egg albumen, mix with soda lime, and heat in a test tube. Note the odor and hold a piece of moist red litmus at the mouth of the tube. What is the gas given off? Explain. This is the decomposition test for proteins.

7. Obtain 20 cc. of fresh milk in your evaporating dish and heat. What are the scums formed? By means of the stirring rod place some of the scum in a test tube and apply the xanthoproteic test (see 4 above). Result?

B. Casein (Soluble in Hot and Cold Water).

1. Is casein soluble in hot water? How do you know? 2. To a portion of the milk used in A, 7 add dilute hydrochloric acid or acetic acid. Result?

To another portion add rennin and warm gently. Allow it to cool for five minutes. Result?

3. To a part of the casein apply the burning test. Result? 4. Apply the xanthoproteic test. Result?

5. Apply the Millon's test. Result?

6. Apply the decomposition test, using soda lime. Result?

QUESTIONS

1. If albumen and casein were in a solution together, how could you separate one from the other?

2. What are some of the tests for albumen and casein?

EXPERIMENT 44

The Globulins and Albuminoids

Note to instructor: Have part 1 of A done at home. The gluten loaves should be submitted for approval and credit.

MATERIALS.

Flour, nitric acid, ammonia, Millon's reagent, soaked beans, bones soaked in hydrochloric acid for a week, soup bones, hair or feathers, sodium hydroxide 4 N, sodium plumbite solution.

Note: Sodium plumbite solution may be prepared by adding sodium hydroxide to lead acetate solution until the precipitate first formed dissolves on heating.

APPARATUS.

Muslin bag, test tubes, evaporating dish.

A. The Globulins (Insoluble in Hot or Cold Water).

Gluten is the globulin found in wheat and other cereals. 1. Into a cup full of flour stir just enough water to make a heavy dough. Place the dough in a muslin bag and knead it in the hand in a running stream of water till the water runs through clear. What part of the flour is removed in this manner? Examine the gluten remaining in the bag. What are its physical properties? Is it soluble in cold water? Leave about one fourth of the gluten in the wet muslin bag and take it to the laboratory for the chemical tests. Bake the other three fourths in a moderate oven. Result? Take the gluten loaf to the instructor for credit.

2. Place a piece of unbaked gluten about the size of a bean in a test tube; add water and boil. Is gluten soluble in hot water?

3. Place a similar piece in your evaporating dish. Heat and note the odor.

4. Apply the xanthoproteic test. Result?

5. Apply the Millon's test. Result? Is gluten a true protein ?

6. Myosin is the globulin found in meat. Burn a small piece of meat and note the odor. Apply the xanthoproteic test. Result?

7. Legumen is the globulin in peas and beans. Burn half a bean that has soaked overnight. Result? Apply the xanthoproteic test to half a soaked bean. Is a protein present?

B. Albuminoids or Gelatinoids (Soluble in Hot Water, Forming Jellies on Cooling).

Collagen is the protein found in cartilage, skin, and bones. 1. (Instructor's experiment.) Boil for some time a soup bone (chiefly tendons and bone). Strain off the clear liquid and cool it. A jelly is formed.

2. Soak bones in hydrochloric acid for 2 or 3 days or a week. Neutralize the acid with sodium carbonate. Then boil the soft bone. Allow to cool. A jelly is formed. Commercial gelatine is made from bones.

Keratin is a very insoluble protein containing much sulfur. Found in hair, hoofs, and nails.

3. Burn some hairs or feathers and note the odor.

4. Boil some hair or feathers with strong NaOH. Add sodium plumbite solution. A black precipitate of lead sulfide shows the presence of sulfur in keratin.

XI. DIGESTION OF FOOD

The body is composed of water, proteins, fats, and mineral matter. The average daily ration contains about 100 grams of protein, 100 grams of fat, and 420 grams of carbohydrates,