Allot is the proportion of a baser metal mixed with a finer or purer, as when copper is mixed with gold, etc.

Amalgam is a compound of mercury and a metal - a soft alloy.

All compositions of copper contract in the admixture, and all amalgams expand.

In the manufacture of alloys and compositions, the more infusible metals should be melted first.

In compositions of brass, as the proportion of zinc is increased, so is the malleability decreased.

The tenacity of brass is impaired by the addition of lead or tin.

Steel alloyed with 5/100 th part of platinum, or silver, is rendered harder, more malleable, and better adapted for cutting instruments.

Any alloy which is slowly heated and gradually cooled (annealed, that is), is softer than when the compound is suddenly chilled; hence the hardness of chill-cast iron.

In moulding. no casting of any kind should be removed until it is cooled down to within a few degrees of the atmosphere; and in open sand castings, a thick covering of sand should be applied to retain the heat.

Neglect of this caution is certain to weaken the piece, and frequently is the cause of accidents.

ALLOYS AND COMPOSITIONS.

Copper.

Zinc.

Tin.

Nickel.

Lead

Antimony

Bismuth.

Silver

Cobalt of Iron.

Iron.

Arsenic.

Argentan.....................

55.

24.

21.

Argentiferous....

50.

2.5

2.5

40.

2.5

2.

.....z

Babbitt's metal*.........

8.7

......

89.

7.3

• ■••

Brass, common............

S4.3

6.2

10.6

" "

75,

25.

" " hard....

79.3

6.4

14.3

" Mathematical

Instruments.

92.2

7.8

" pinchbeck.........

80.

90.

" red tombac.........

88.8

11.2

" rolled...............

74.8

22 3

3.4

" tutenag............

50.

31.

.........

19.

" very tenacious..

88.9

2.8

8.8

" wheels, valves...

90.

10.

" white.................

10.

80.

10

.....

. ...

" wire.................

07.

SSL

" yellow, fine...........

66.

34.

" Britannia metal........

25.

to,

When fused, add...

. ..

25.

25.

Bronze, red...............

87.

13.

....

" red..................

86.

11.1

2.9

" yellow........

67.2

31.2

1.6

" Cymbals.....

80.

20.

" gun metal, large

90.

10.

.....

« .....

" " small

7.

" Medals...........

9.1.

7.

• ••••

" Statuary...........

91.4

6 5

1.4

1.7

Chinese silver............

65.1

19 3

13.

2.48

.12

.....

.......

Chinese white copper..

40.4

25.4

2.6

31.6

Church bells................

80.

6.6

10.1

4.3

• ••••

" ............

69.

31.

Clock bells....................

72.

26.5

1.5

........

Cocks, Musical bells..

87.5

12.5

.....

German silver.............

88,8

33.4

83.3

" " ..........

40.4

25.4

31.6

2.6

.....

" " fine......

49.5

24.

24.

2.5

.......

Gongs................

81.6

18.4

............

House bells.............

77.

23.

Lathe bushes...............

SO.

20.

Machinery bearings..

87.5

12.5

.....

" " hard

77.4

7.

15.6

Metal that expands in cooling....................

75.

16.7

8.3

.....

Muntz metal...................

60.

40.

.....

Pewter, best..................

86.

14.

.....

" ...............

80.

20.

......

Printing characters.....

......

......

......

......

80.

20.

.....

Sheathing metal...........

58.

45.

.....

Speculum " .........

66.

22.

.....

12.

" "

50.

21.

29.

....

Telescopic mirrors......

66.6

33.4

.....

Tempert........................

33.4

66.6

.....

Type and stereotype plates ....................

69.

15.5

15.5

White metal................

7 4

7.4

28.4

......

......

50.8

.....

" " hard........

69.8

25.8

4.4

.....

Oreide.........................

73.

12.3

Magnesia.........4.4 Crin of tartar 6.5

Sal-ammoniac 2.5 Quick-lime ...1.33

*See page 164 for directions. †For adding small quantities of copper.