and adding
water. 2. Which sample contains pure vanilla extract? 3. State the
principle underlying this test.

Experiment No. 12

Testing Olive Oil for Cotton Seed Oil

Pour into a test tube 5 cc. of the oil to be tested and 5 cc. of
Halphen's Reagent. Mix thoroughly. Plug the test tube loosely with
cotton, and heat in a bath of boiling saturated brine for 15 minutes. If
cotton seed oil is present, a deep red or orange color is produced. Test
two samples and compare.

Halphen's Reagent.--Mix equal volumes of amyl alcohol and carbon
disulphid containing about one per cent of sulphur in solution.

(Adapted from Leach, "Food Inspection and Analysis.")

Experiment No. 13

Testing for Coal Tar Dyes

Dilute 20 to 30 cc. of the material to 100 cc.; boil for 10 minutes with
10 cc. of a 10 per cent solution of potassium bisulphate and a piece of
white woolen cloth which has previously been boiled in a 0.1 per cent
solution of NaOH and thoroughly washed in water. Remove the cloth from
the solution, wash in boiling water, and dry between pieces of filter
paper. A bright red indicates coal tar dye. If the coloring matter is
entirely from fruit, the woolen cloth will be either uncolored or will
have a faint pink or brown color which is changed to green or yellow by
ammonia and is not restored by washing. This is the Arata test.

(Adapted, Winston, Conn. Experiment Station Report.)

1. Describe Arata's wool test for coal tar dyes. 2. What is the
appearance of the woolen cloth when the coloring matter is entirely from
fruit? 3. What effect has NH_{4}OH upon the color? 4. Why is NaOH used?
5. Why may not cotton cloth be used instead of woolen? 6. What can you
say of the use of coal tar dyes in foods?

Experiment No. 14

Determining the Per Cent of Skin in Beans

Place in an evaporating dish 10 gm. of beans, 50 cc. of water, and 1/2
gm. of baking soda. Boil 10 minutes or until the skins are loosened,
then drain off the water. Add cold water and rub the beans together till
the skins slip off. Collect the skins, place on a watch glass and dry in
the water oven for 1/2 hour. Weigh the dried skins and calculate the per
cent of "skin."

1. What does the soda do? 2. What effect would hard limewater have upon
the skins? 3. How does removal of skins affect food value of beans and
digestibility?

Experiment No. 15

Extraction of Fat from Peanuts

Shell three or four peanuts and with the mortar and pestle break