EXAMPLE. How many units of heat are required to melt

10 lb. of zinc from a temperature of 60° F.?

SOLUTION. The specific heat of zinc is found from the table to be .0956. Hence, the number of heat units necessary to raise it to the melting point is 10 X (680 — 60) × .0956 = 592.72. Latent heat of fusion = 50.63 heat units. Hence, the total number of heat units required is 592.72 + 10 X 50.63 1,099.02.

EXAMPLE.-A wrought-iron bar 22 ft. long is heated from

70° to 300°. How much will it lengthen? SOLUTION. 22 × (300—70) X .00000686 .41654 in.

=

.0347116 ft.

=

ALLOYS.

==

Silver, T= : Tin,

NOTE.-A = Antimony, B = Bismuth, C = Copper, G. Gold, I Iron, L = Lead, N = Nickel, S Z = Zinc.

=

Proportions.

2 C, 1Z

32 C, 10 Z, 1.5 T

20 C, 1.25 Z, 2.5 T

25 C, 2 Z, 4.5 T
8 C, 5 Z, 1 T

SC, 1 T

Metal, expands in cooling 75 L, 16.7 A, 8.3 B

WEIGHT OF ROUND AND SQUARE ROLLED IRON. From in. to 91⁄2 in. in Diameter, and 1 ft. in Length.

WEIGHT OF SHEET LEAD.

Thickness. W'ght. Thickness. W'ght. Thickness. Wight.

203.260

9

258.800

91

215.040 273.792

913

2

Inches.

Lb.

Inches.

Lb.

Inches.

Lb.

PROPORTIONS OF THE UNITED STATES STANDARD SCREW THREADS, NUTS, AND BOLT HEADS.

The threads have an angle of 60°, with flat tops and bottoms, and are of the following proportions:

Notation of letters. All dimensions in inches.

3 D
+

1

0 = 1.155 i.

=

d=D-