per cent solution), dried, and
brushed. Or sprinkle with a 10 per cent solution of soda, drying,
brushing, and noting any change in the color.

_a._ Is there any change in color after the lime water
has been removed from the cloth?

_b._ With what may the action of the lime water or soda
be compared?

=Experiment 43--Testing Rubberized Fabrics=

Materials: Rubberized fabrics.

A great many rubberized fabrics are used for hospitals, domestic
purposes and for clothing. On account of the high price of excellent
rubberized fabrics a great many substitutes are placed on the market
that are satisfactory to the eye, but have not the wearing qualities
for the service they are intended to render.

Strength and Resistance to Scratching.--In order to test a rubberized
fabric to see if it has the necessary strength to stand everyday use,
see if it is possible to scratch it with the finger nail. Then crease
it and crumple it between the hands. Then spread it out very carefully
and notice whether there are any broken places. If there are it should
be rejected.

Waterproof Qualities.--A rubberized fabric should be waterproof. A
sample may be tested by forming a bag with it and filling it with
water. Crumple the bag while it is filled with water. Notice whether
it cracks or leaks.

Examine various rubberized fabrics and notice whether they are
substantial.

=Experiment 44--Test for Vegetable and Animal Fiber=

Apparatus: Acid, fire.
Materials: Warp and filling threads of cotton and woolen fabrics.
Reference: _Textiles_, page 239.

_Directions_

One of the most useful tests is to see whether an article is made of
wool, cotton, or silk, and if a composition of two or more materials,
to estimate the percentage of each. Practical experience can teach one
much in this respect, and in many cases inspection is quite
insufficient. A more reliable test is to burn a piece of material and
notice how it burns.

Take a sample of a woolen and cotton fabric; separate the warp and
filling and untwist one piece of warp and one piece of filling yarn.
Burn a piece of untwisted yarn and notice whether it burns slowly and
curls up into a black crisp cinder leaving a disagreeable smell, or
burns with a flash leaving a light ash behind.

_Questions_

1. Describe the burning process.

2. What is the burning test for vegetable fiber?

3. What is the burning test for animal fiber?

Repeat the s