Man's physical universe

xanabras

COMBUSTION 653

their other properties, has resulted in their almost universal adoption

for chemical laboratory glassware.

Colored glass is obtained by adding small traces of the oxides of

heavy metals; thus cobalt oxide imparts a blue color; selenium oxide,

a ruby red; chromium trioxide, a green; manganese dioxide, a violet;

and iron oxide, an amber color.

One of the latest developments in building is the use of glass blocks.

These blocks can be improved as to their insulating and light-diffusing

properties by sealing sheets of Fiberglas into them.

Melted glass can be passed through tiny holes or pulled out to produce

threads that are less than one tenth of the diameter of a human

hair. These fibers can be spun into moistureproof, verminproof, rotand

mildewproof, fireproof cloth. Because of their electrical insulating

properties glass fabrics are used in the electrical industry for such applications

as battery-plate separators. At present glass fabrics are too

harsh for wearing apparel in direct contact with the skin and have

limited utility in uses involving much wear or flexing. Glass wool is

widely used in air conditioning as a filtering medium and an insulating

material.

Mineral wool, a product similar to glass wool, is likewise widely used

for heat and sound insulation. The raw materials for mineral wool are

slags, formerly the waste products from the refining of metals, to

which certain rock materials are sometimes added to impart the desired

properties to the final product. The mineral wool is usually produced

by melting the slag or slag-rock mixture and then blowing air or steam

under high pressure into a small stream of the molten material.

STUDY QUESTIONS

1. Differentiate between quicklime and hydrated lime.

2. What is the composition of mortar, and what reaction takes place when it

sets?

3. Why is it desirable to keep concrete wet while it is setting?

4. Discuss mineral wool as to (a) its preparation, and (b) its uses.

5. Discuss Portland cement as to (c) composition, (b) raw materials, and

(c) method of manufacture.

6. Discuss glass as to (o) composition, (b) raw materials, (c) types of glass, and

(d) modern uses.

7. Discuss the progress that man has made in duplicating the materials produced

in nature.

8. Discuss plaster of Paris as to (a) its preparation, (b) its uses, and (c) what

happens when it sets.

9. Discuss the nature of incendiary bombs.

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