them
into small pieces. Place in a test tube and pour over them about 10 cc.
of ether. Cork the test tube and allow it to stand 30 minutes, shaking
occasionally. Filter on to a watch glass and let stand until the ether
evaporates, and then observe the fat.

1. What is the appearance of the peanut fat? 2. What is the solvent of
the fat? 3. What becomes of the ether? 4. Why should the peanuts be
broken into small pieces?

Experiment No. 16

Microscopic Examination of Milk

Place a drop of milk on a microscopical slide and cover with cover
glass. Examine the milk to detect impurities, as dust, hair, refuse,
etc. Make drawings of any foreign matter present.

Experiment No. 17

Formaldehyde in Cream or Milk

To 10 cc. of milk in a casserole add 10 cc. of the acid reagent. Heat
slowly over the flame nearly to boiling, holding the casserole in the
hand and giving it a slight rotary movement while heating. The presence
of formaldehyde is indicated by a violet coloration varying in depth
with the amount present. In the absence of formaldehyde the solution
slowly turns brown.

Acid Reagent.--Commercial hydrochloric acid (sp. gr. 1.2) containing 2
cc. per liter of 10 per cent ferric chlorid.

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

1. How may the presence of formaldehyde in milk be detected? 2. Why in
this test is it necessary to use acid containing ferric chlorid? 3.
Describe the appearance of the two samples of milk after adding the acid
reagent and heating. 4. Which sample showed the presence of
formaldehyde?

Experiment No. 18

Gelatine in Cream or Milk

To 20 cc. of milk or cream in a beaker add 20 cc. of acid mercuric
nitrate and about 40 cc. of H_{2}O. Let stand for a few minutes and
filter. Filtrate will be cloudy if gelatine is present.

Add 1/2 cc. of a dilute solution of picric acid--a heavy yellow
precipitate indicates gelatine.

Acid Mercuric Nitrate.--1 part by weight of Hg, 2 parts HNO_{3} (sp.
gr. 1.42). Dilute 25 times with water.

Experiment No. 19

Testing for Oleomargarine

Apply the following tests to two samples of the material:

Boiling or Spoon Test.--Melt the sample to be tested--a piece about
the size of a chestnut--in a large spoon, hastening the process by
stirring with a splinter. Then, increasing the heat, bring to as brisk a
boil as possible and stir thoroughly, not neglecting the outer edges.
Oleomargarine and renovated butter boil noisily, sputte