The preceding ten tables of Tralles contain allthat is requisite for the determination of the volumeof alcohol in a liquid; they have been constructedon the principle of the tables of Gilpin. Trallesexperiments were made in 1811, he found thatGilpin’s alcohol, so far from being absolute, con-tained 108 per cent, of water. Since then furtherextensive researches have been made by manyeminent chemists, the most important being those ofGay-Lussac , who in 1824 drew up much more exten-sive tables, which require scarcely any interpolation.
Gay-Lussac ’s instrument is like a glass hydro-meter, the stem of which is divided into degreeslike that of Tralles, to indicate the percentage ofalcohol by volume, but the temperature at whichthe graduation was made was 15° C. or 59° Fahr.,instead of 60°'Fahr., as the normal temperature ofTralles’ tables. Water is taken as unity at thistemperature. The stem of the instrument is divided,from the point at which it stands in water, into 100divisions, so that eaoh on the scale is equal to one percent, of alcohol; the 100th division indicates pureor absolute alcohol, while 0 or zero equals purewater at 15 C.
The instrument, if immersed in an alcoholic liquorat 59° Fahr., marks the strength by the number ofdegrees below the surface; thus, if the alcoholometerstands at 57 in a liquid at 59°, such a solution con-tains 57 per cent, by volume of alcohol.
In consequence of the temperature 59° Fahr.(15° C.) being taken by Gay-Lussac , as the funda-mental numbers for determining the relation, thepercentage of alcohol and the specific gravities arcin a slight degree different from those of Tralles,but the variation is so minute that in practice itmay be overlooked.
In the annexed table the fundamental numbers ofthe centesimal amount per volume, together withthe specific gravities of the different alcoholic mix-tures at 59° Fahr. (15° C,), are given:—
Ter cent,of alcoholby volume.
Spoeilie gravityof the liquidat Ju°.
Fcr cent,of alcoholby volume.
Specific gravity
Of the liquidat 5b°.
100
0-7947
60
0-9141
95
0-8168
55
0-9248
90
0-8346
50
0-9348
85
0-8502
45
0-9440
80
0-8645
40
0-9523
75
0-8799
35
0-9595
70
0*8907
10
0*9656
65
0*9027
0
1*0000
The first table by Gay-Lussac is denominatedTable for the real strength of spirits, and correspondswith Table VIII. of Tralles. This table gives thetrue percentage by volume at 59° Fahr. (15° C.)from the observed percentage of the alcoholometerat any other temperature. Two numbers are placedin the same horizontal column, and vertical to eachother: those in the top are the observed centesimalquantities of the alcoholometer, while the large figuresin the vertical column below them give the real per-centages at 59° Fahr. when tested at the temperaturefound in the left-hand vortical column. The num-
bers in small figures beneath the real percen-tages denote the bulk at 59° Fahr. (15° C.) of 1000measures of liquid; this number, multiplied by thereal percentage under which it stands, gives theabsolute quantity of alcohol at the temperature atwhich the experiment is performed.
To read the table, suppose an alcoholic liquid of50 strength indicated by the alcoholometer at a tem-perature of G8° Fahr., the observed percentage—50—is sought in the horizontal column at the top; inthe vertical column beneath this and on a line with68°, in the temperature column at the left hand, willbe found the number 48-2, which is the quantity ofreal spirit at 59°. The number 996, in small figuresbelow the indicated strength at 59°, is the bulkor volume which 1000 volumes would occupy atthe standard temperature ; and by multiplying thisnumber by the proper strength, and dividing theproduct by 1000, the strength or true volume of spiritin 1000 of the liquid is ascertained; thus—
996 + 48-2 = 48007-2 + 1000 = 4.8-00, the percentage;
hence, 100 volumes of the liquor at 58° contain 48volumes of absolute alcohol at 59°.
Morazeau constructed, with one of Gay-Lussac ’salcoholometers, a table somewhat more in detail,which differs slightly from the preceding in thefigures denoting the density, although they havereference to the same temperature.
When, however, the liquors to be tested stand ata higher degree than 59° Fahr. (15° C.), no provi-sion is made to discover the true amount of spirit,which must then be sought either by other tables orby the calculation given earlier.
Per centof alcoholby volume.
Specific
gravity.
Ter centof alcoholby volume.
Specific
gravity.
Per centof alcoholby volume.
Specific
gravity.
0
1-000
34
0-962
68
0*896
1
0*999
35
0*960
69
0-893.
2
0-997
36
0*959
70
0-891
3
0*996
37
0-957
71
0*888
4
0*994
38
0*956
72
0*884
5
0*993
39
0-954
73
0-881
6
0*992
40
0-953
74
0*879
7
0-990
41
0-951
75
0-876
8
0*989
42
0-949
76
0-874
9
0-988
43
0-948
77
0-871
10
0-987
44
0-946
78
0-868
11
0-986
45
0-945
79
0-865
12
0-984
46
0-943
80
0-863
13
0-983
47
0-941
81
0-860
14
0-982
48
0-940
82
0-857
15
0-981
49
0-938
83
0-854
16
0-980
50
0-936
84
0-851
17
0*979
51
0-934
85
0*848
18
0-978
52
0-932
86
0*845
19
0-977
53
0*930
87
0*842
20
0*976
54
0*928
88
0*838
21
0-975
55
0*926
89
0-835
22
0*974
56
0*924
90
0-832
23
0*973
57
0*922
91
0-829
24
0*972
68
0-920
92
0-826
25
0*971
59
0-918
93
0-822
26
0*970
60
0-915
94
0-818
27
0*969
61
0-913
95
0-814
28
0*968
62
0-911
96
0-810
29
0-967
G3
0-909
97
0-S05
30
0*966
64
0-906
98
0*800
31
0-965
65
0-904
99
0-795
32
0-964
06
0*902
100
0-747
33
0-963
67
0-899