The "'original gravity" of beer is the specific gravity of the wort from which it was made, before fermentation. This is ascertained by computation from data given by the alcoholic content and the malt extract contained in the dealcoholized liquid. The specific gravity of the alcoholic distillate (or the specific gravity of the alcohol evaporated, if the indirect method is used) when subtracted from 1.000 gives a number called the "spirit indication." The degrees of gravity lost are then ascertained by reference to the table given below. The degrees found are added to the specific gravity of the dealcoholized beer, and the number thus obtained is the original gravity.

The following table was calculated by Graham, Hofmann, and Bedwood from actual experiments on malt worts fermented under normal conditions:

1 The following duplicate determinations show very satisfactory agreement in the results obtained by using a small quantity for drying:

No. 4800.

No. 4801.

No. 4804.

No. 4817.

1...........................

4.25

5.40

4.52

4.67

2...........................

4.16

5.40

4.58

4.62

Degrees of

spirit indication.

.0

.1

.2

.3

.4

.5

.6

.7

.8

.9

0

.3

.6

.9

1.2

1.5

1.8

2.1

2.4

2.7

1

3.0

3.3

3.7

4.1

4.4

4.8

5.1

5.5

5.9

6.2

2

6.6

7.0

7.4

7.8

8.2

8.6

9.0

9.4

9.8

10.2

3

10.7

11.1

11.5

12.0

12.4

12.9

13.3

13.8

14.2

14.7

4

15.1

15.5

16.0

16.4

16.8

17.3

17.7

18.2

18.6

19.1

5

19.5

19.9

20.4

20.9

21.3

21.8

22.2

22.7

23.1

23.6

6

24.1

24.6

25.0

25.5

20.0

26.4

26.9

27.4

27.8

28.3

7

28.8

29.2

29.7

30.2

30.7

31.2

31.7

32.2

32. 7

33.2

8

33.7

34.3

34.8

35.4

35.9

36.5

37.0

37.5

38.0

38.6

9

39.1

39.7

40.2

40.7

41.2

41.7

42.2

42.7

43.2

43.7

10

44.2

44.7

45.1

45.6

46.0

46.5

47.0

47.5

4X. 0

48.5

11

49.0

49.6

50.1

50.6

51.2

51.7

52. 2

52.7

53.3

53.8

12

54.3

54.9

55.4

55.9

56.4

56.9

57.4

57.9

58. 4

58.9

13

59.4

60. 0

60.5

61.1

61.6

62.2

62.7

63.3

63. 8

64.3

14

64.8

65.4

65.9

66.5

67.1

67.6

68.2

68 7

69. 3

69.9

15

70.5

71.1

71.7

72.3

72.9

73.5

74.1

74.4

75.3

75.9

A content of acetic acid above 0.1 per cent. somewhat vitiates the results given by the table, and a correction is necessary. The manner of making this correction may be ascertained by consulting Allen,1 or any of the standard works, which give also tables for the calculation of the actual weight of malt used in the wort.

Below is given a table showing the results obtained from the samples analyzed, by the direct and indirect methods :

Comparison of direct and indirect methods of estimating alcohol and extract in malt liquors.

Serial No.

Number of analysis.

Alcohol direct.

Alcohol by calculation.

Extract direct.

Extract by calculation.

Original gravity by distillation.

Original gravity by evaporation.

Per ct.

Per ct.

Per ct.

Per ct.

4800............

1

4.28

4.33

4.18

4.56

1. 0505

1.0506

4801............

2

4.42

5.40

6.03

1. 0573

4802...........

3

4.55

4.51

5.71

6.44

1.0607

1. 0596

4803............

4

4. 18

3.96

5.05

5.52

1. 0533

1. 0516

4804............

5

5.53

5.39

4.55

5.03

1.0628

1.0616

4805............

4806............

6

7

4.40 4.29

4.08 4.08

6.15 5.22

6.44 5.67

1. 0590 1.0549

1.0562 1.0531

4807............

8

4.35

3.84

5.09

5.54

1.0549

1. 0507

4808............

9

4.52

4.39

5.94

6.64

1. 0609

1. 0594

4810............

10

3.84

3.67

7.05

7.82

1.0601

1. 0584

4811............

11

4.36

4.08

4.63

5.29

1. 0539

1.0516

4812............

12

4.29

3.90

5.18

5.57

1.0545

1.0513

4813...........

13

4.63

4.33

5.86

6.32

1. 0607

1. 0576

4814............

14

4.71

4.57

4.91

5.62

1.0585

1.0569

4815............

15

4.30

3.90

4.83

5.39

1.0538

1. 0506

4816............

16

3.86

5.62

4817............

17

4.28

3.90

4.64

6.36

1. 0577

1. 0545

4818............

18

4.68

4.33

6.82

7.24

1.0650

1.0613

4819............

19

6.24

5.83

3.46

4.17

1.0647

1.0616

4820............

20

5.66

5.39

4.42

4.90

1. 0633

1.0611

4821............

21

6.13

5.77

5.90

6.33

1. 0728

1. 0697

4822............

22

5.30

5.51

3.94

4.54

1. 0587

1. 0605

4823............

23

5.38

5.07

3.05

3.25

1. 0543

1. 0520

4824............

24

3.86

3.43

6.24

6.63

1. 0553

1. 0517

4825............

25

4.59

4.20

5.38

5.80

1. 0581

1.0545

4826............

26

5.25

4.76

6.02

6.55

1. 0669

1. 0623

4827............

27

6.92

6.42

5.55

6.09

1.0781

1. 0741

4828............

28

4.89

4.39

8.19

8.83

1.0736

1.0683

4842............

29

4.22

3.49

5.88

6.31

1.0570

1. 0509

4843............

30

' 4.22

3.37

5.84

6.23

1. 0567

1. 0493

4844............

31

4.16

3.37

5.88

6.26

1.0563

1. 0494

4845............

32

5.06

4.14

6.26

6.69

1.0660

1. 0576

4.73

4.41

5.40

5.94

1. 0600

1.0569

1Commercial Organic Analysis, 2d edit., Vol. I.