17
11.
Display unit of the instrument
The instrument designed to measure concentration of liquid using the refraction of light.
The "Refractive Index" is a unit which expresses the refraction of light. Individual substances
have a value of Refractive Index of their own and the following substances have a value of
Refractive Index at 20℃ as shown below.
Air .................................. 1
Water ............................ 1.33299
Salad oil ....................... 1.47
White plate glass ..... 1.52
Diamond ...................... 2.55
The Refractive Index of water solution increases grandually from 1.33299 of water as
dissoloved components increase. Scales of the instrument are set up by unit of weight % of
sucrose dissolved in water. This is called Brix(%) (Brix (percentage)). If 10g sucrose is dissolved
in 90g water, for example, this solution is expressed by Brix 10%. There exists a fixed relation
between this Brix(%) and the aforementioned Refractive Index and the relative expression is
determined by ICUMSA (International Committee of Uniform Method of Sugar Analysis). Based
on this relative expression, the instrument converts the Refractive Index of sample (measured
result) to Brix(%) and display its value.
Table 11-1 Table of Refractive Indexes and Brix(%)
1974 ICUMSA
％
％
％
％
％
0
1.33299 20
1.36384 40
1.39986 60
1.44193 80
1.49071
1
1.33442 21
1.36551 41
1.40181 61
1.44420 81
1.49333
2
1.33586 22
1.36720 42
1.40378 62
1.44650 82
1.49597
3
1.33732 23
1.36889 43
1.40576 63
1.44881 83
1.49862
4
1.33879 24
1.37060 44
1.40776 64
1.45113 84
1.50129
5
1.34026 25
1.37233 45
1.40978 65
1.45348 85
1.50398
6
1.34175 26
1.37406 46
1.41181 66
1.45584 86
1.5067
7
1.34325 27
1.37582 47
1.41385 67
1.45822 87
1.5094
8
1.34477 28
1.37758 48
1.41592 68
1.46061 88
1.5121
9
1.34629 29
1.37936 49
1.41799 69
1.46303 89
1.5149
10
1.34782 30
1.38115 50
1.42009 70
1.46546 90
1.5177
11
1.34937 31
1.38296 51
1.42220 71
1.46790
12
1.35093 32
1.38478 52
1.42432 72
1.47037
13
1.35250 33
1.38661 53
1.42647 73
1.47285
14
1.35408 34
1.38846 54
1.42863 74
1.47535
15
1.35568 35
1.39032 55
1.43080 75
1.47787
16
1.35729 36
1.39220 56
1.43299 76
1.48040
17
1.35891 37
1.39409 57
1.43520 77
1.48295
18
1.36054 38
1.39600 58
1.43743 78
1.48552
19
1.36218 39
1.39792 59
1.43967 79
1.48811
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