Hydrometer Temperature Corrections
Posted to HBD #963, 9/7/92, by Christopher Lyons
Following up on the specific gravity of water as a
function of temperature.... The earlier equation was
based on data for 50F-to-105F. Since the equation
was from a polynomial fit, it should not be trusted
for predicting SG outside this temperature range.
The data below was obtained using the "Handbook of
Chemistry and Physics (CRC)", and is valid for a
temperature range between 0 and 212F.
Temp (C) Temp (F) Density Correction relative to 59F
------- -------- ------- --------------------------
0 32 0.99987 -0.74
3.98 39.16 1.00000 -0.87
5 41 0.99999 -0.86
10 50 0.99973 -0.6
15 59 0.99913 0
18 64.4 0.99862 0.51
20 68 0.99823 0.9
25 77 0.99707 2.06
30 86 0.99567 3.46
35 95 0.99406 5.07
38 100.4 0.99299 6.14
40 104 0.99224 6.89
45 113 0.99025 8.88
50 122 0.98807 11.06
55 131 0.98573 13.4
60 140 0.98324 15.89
65 149 0.98059 18.54
70 158 0.97781 21.32
75 167 0.97489 24.24
80 176 0.97183 27.3
85 185 0.96865 30.48
90 194 0.96534 33.79
95 203 0.96192 37.21
100 212 0.95838 40.75
The correction term was computed relative to
15C (59F). It may be easily calculated relative
to any temperature. A third order polynomial fit
to this data was also very good (R**2 = 0.999969):
Correction(@59F) =
1.313454 - 0.132674*T + 2.057793e-3*T**2 - 2.627634e-6*T**3
where T is in degrees F.
This equation should be good for the entire temperature range
of interest