1. Place a piece of white cotton cloth and a piece of woolen material in small dishes. Cover with 50 per cent solution of nitric acid. The wool fibers will turn yellow. The cotton remain white. If a piece of wool cloth was mixed with cotton, how would the test prove it?
2. Boil samples of cotton and wool together; then samples of cotton and silk together, for fifteen minutes in a 5 per cent solution of caustic potash. The animal fibers will dissolve, the cotton will remain. Of what use would this test be?
3. Moisten samples of cotton and of wool with Millon's reagent. Place in porcelain dishes and heat gently. The animal fibers will become red; the vegetable are unchanged.
4. Material made of cotton and linen and sold for all linen can be tested. Place fringed sample in a porcelain dish. Heat gently in 50 per cent solution of caustic potash for two minutes. Remove with glass rod and dry between blotting papers. The linen will be dark yellow in color and the cotton white or light yellow.
So we have learned a few tests of different kinds. There are many more. When you go to high school you can learn about others. The Pleasant Valley girls enjoyed making these tests with Miss James' help. Perhaps you may be able to try them with your teacher.
EXERCISES AND PROBLEMS
1. Try the above chemical tests with your teacher's help.
2. Try some of the other tests for adulterations.
3. Tell four ways in which materials are adulterated.
Lesson 7
HOW PATTERN IS MADE IN CLOTH
Barbara said she never could quite see how pattern is made in cloth. There seem to be so many different kinds of patterns. Miss James explained about this. She said there are several ways of making patterns. Some are printed; others woven; some embroidered. Have you discovered this?
Patterns are often woven. Do you remember, when you studied about linen, you learned that the Jacquard loom has a series of cards above it which are able to control the pattern? Wonderful silks and beautiful velvets and brocades as well as damask table linen are made in this way by weaving. Patterns of stripes and plaids are also made by the loom in weaving. Sometimes the warp or the filling threads are colored; and this color forms patterns in stripes or squares. See if you have any pieces in your surprise box in which pattern is made by colored threads of warp or woof.
Try to find some woven patterns made by the Jacquard loom in silk or linen. Think of all the beautiful ribbons, silks, tablecloth damasks, towels, and napkins; all such patterns are woven by the loom. Plain patterns like basket weave, twill, diagonal, satin weave, are also made by weaving. See if you can work out some of these patterns on your school loom.