ALCOHOL. —Alcoiiolometuy. Fownes’ Table. 147
Care must be taken that the mercury is entirely inthe bulb of the thermometer before it is fixed to thestem; and salt must always be added when deter-mining the boiling point, except in the case ofwater.
The instrument is very useful for testing therelative quantity of fruit and alcohol in normalwines.
Fownes drew up a table of the value, in absolutealcohol, of spirits of different specific gravities, whichis given below.
The table was formed synthetically; absolute alco-hol and distilled water were weighed out in therequired proportions, mixed in small closely-stoppedbottles, and well shaken together. After standingthree or four days, the mixtures were brought to thetemperature of 60° Fahr. exactly, and their specificgravities determined with great care. When two orthree days more had elapsed, the specific gravity wasagain taken, but in no case had any further contrac-tion occurred. Neither was the specific gravity of amixture, containing nearly equal parts alcohol andwater, which had been so examined, changed by beinginclosed in a strong accurately-stoppered bottle, andheated for some time to a temperature above its boilingpoint.
In this manner, every alternate number in the table—every even number—was obtained by direct experi-ment ; the others were then incorporated.
TABLE OP TIIE PROPORTION BY WEIGHT
Of real or absolute alcohol contained in 100 parts of spirits ofdifferent specific gravities, at the temperature of 60° Fahr.
Specific
gravity.
Per centngeof alcohol.
Specific
gravity.
Per centngeof alcohol.
Specific
gravity.
Per cfntngoof alcohol.
•9991
0-5
•9511
34
•8769
68
•9981
1
•9490
35
•8745
69
•9965
2
•9470
36
•8721
70
•9947
3
•9452
37
•8696
71
•9930
4
•9434
38
•8672
72
•9914
5
•9416
39
•8649
73
•9898
6
•9396
40
•8625
74
•9884
7
•9376
41
•8603
75
•9869
8
•9356
42
•8581
76
-9855
9
•9335
43
•8557
7?
•9841
10
•9314
44
•8533
78
•9828
11
•9292
45
•8508
79
•9815
12
•9270
46
•8183
80
•9S02
13
•9249
47
•8459
81
•9789
14
•9228
48
•8434
82
•9778
15
•9206
49
•8408
83
•9766
16
•9184
50
•8382
84
•9753
17
•91G0
51
•8357
85
•9741
18
•9135
52
■8331
86
•9728
19
■9113
53
•8305
87
•9716
. 20
•9090
54
•8279
88
•9704
21
•9069
55
•8254
89
•9691
22
•9047
56
•8228
90
•9678
23
•9025
57
•8199
91
•9665
24
•9001
58
•8172
92
•9652
25
•8979
59
•8145
93
•9638
26
•8956
60
•8118
94
•9G23
27
•8932
61
•8089
95
•9609
28
■8908
62
•8061
96
•9593
29
•8886
63
•8031
97
•9578
30
•8863
64
•8001
98
•9560
31
•8840
65
•7969
99 ’
■9544
32
•8816
66
•7938
100
•9528
33
•8793
67
The contraction of volume suffered by various mix-tures of alcohol and water, may be rendered obvious
by comparing the actual specific gravities of suchmixtures with their calculated mean densities. InFig. 52, on the next page, in which the verticallines represent the percentage of alcohol by weight,and the horizontal lines the specific gravities, thecalculated mean specific gravities of the mixtures areseen to form a straight diagonal line from corner tocorner, while the actual densities form an irregularcurve with upward convexity, rising quickly to itsmaximum deviation at 30 per cent., running almostparallel with the other line to 50 per cent., andthence declining until it reaches the extremity ofthe scale.
Silbehmann holds that the various means employedfor ascertaining the respective quantities of alcoholand water in mixtures of those liquids possess manydisadvantages. The distillation process is rarely em-ployed, on account of the great skill required in itsapplication, and the length of time the operation de-mands before the results are arrived at. This method,at best, is only applied where accurate and scientifictruth is required, irrespective of delay and toil. Thedensity test is open to error on account of extractivematters being present, which render the specificgravity of the impregnated liquid higher than that ofalcohol, and thus prevent the true amount of spiritfrom being determined with strict accuracy; hencethe excise duty is, in consequence, evaded. Winestested by the density process only indicate aboutone-half their strength; and for this reason Gay-Lussac combines, with the use of his alcoholometricareometer, the distillation test.
He objects likewise to the boiling test of Field’shydrometer, that liquids may be heated beyond theirboiling point without ebullition, and that the ther-mometer, even when immersed in the liquid, mayunder certain circumstances stand several degreesabove the real temperature, which would give rise toa difference in result of four alcoholometric degreesfor every such extra indication. lie also considersthat the barometric variations should be taken intoaccount in some better way. S7 LBERMANn’S arrange-ment to obviate these evils is based upon the dilata-tion of the alcoholic liquid. It is well known thatbetween 32° and 212° Fahr. (0° and 100° C.), thedilatation of alcohol is triple that of water. This ismuch greater between 77° and 122° Fahr. (25° and50° C.)—and may thus be demonstrated:—Poui-water at 25° C. into a thermometer tube, so as tofill the reservoir, and a small portion of the tube upto a certain mark ; then, on heating the thermometerto 50° C. the water will rise a certain distance abovethe mark, and let this point be scratched on the tube;now, if the same quantity of pure alcohol, also at 25°C., be substituted for the water, and heated to thetemperature of 50° C., it will be found to have risenthree and a half times higher than the water. Anymixture of alcohol and water, on being treated in thesame way, will be found to have a mean point ofdilatation between these two, and will be nearer theone or the other, according as either liquid prepon-derates. If, therefore, a series of mixtures of alcoholand water be made, beginning with—