The experimentally obtained values of density, TDS, refractive index, and ultrasonic velocity with varying temperature are reported in Tables 1, 2 and 3 for Tap Water, RO water and Distilled water respectively.
Table 1
Observations for Tap Water
Temperature | TDS | Refractive Index | UV Ultrasonic Velocity (v) (m/s) | Density (ρ) (kg/m3) | Adiabatic Compressibility (β) (m2/N) | Acoustic Impedance (Ry) |
281K | 1060 | 1.414 | 1480 | 1000.716 | 4.562E-10 | 1481059.68 |
282K | 1060 | 1.414 | 1400 | 1000.645 | 5.099E-10 | 1400903 |
283K | 1060 | 1.414 | 1480 | 1000.561 | 4.563E-10 | 1480830.28 |
284K | 1060 | 1.414 | 1440 | 1000.464 | 4.82E-10 | 1440668.16 |
285K | 1060 | 1.414 | 1480 | 1000.354 | 4.564E-10 | 1480523.92 |
286K | 1060 | 1.414 | 1520 | 1000.231 | 4.327E-10 | 1520351.12 |
Table 2
Observations for RO Water
Temperature | TDS | Refractive Index | UV Ultrasonic Velocity (v) (m/s) | Density (ρ) (kg/m3) | Adiabatic Compressibility (β) (m2/N) | Acoustic Impedance (Ry) |
277K | 74 | 1.349 | 1520 | 1000.06 | 4.33E-10 | 1520091 |
281K | 74 | 1.349 | 1480 | 999.935 | 4.57E-10 | 1479904 |
282K | 74 | 1.349 | 1546 | 999.888 | 4.18E-10 | 1545827 |
283K | 100 | 1.414 | 1466.66 | 999.807 | 4.65E-10 | 1466377 |
287K | 100 | 1.414 | 1480 | 999.351 | 4.57E-10 | 1479039 |
288K | 100 | 1.414 | 1440 | 999.206 | 4.83E-10 | 1438857 |
291K | 83 | 1.414 | 1440 | 99.689 | 4.84E-09 | 143552.2 |
293K | 113 | 1.36 | 1490 | 998.32 | 4.51E-10 | 1487497 |
294K | 116 | 1.355 | 1600 | 998.111 | 3.91E-10 | 1596978 |
295K | 116 | 1.355 | 1500 | 997.889 | 4.45E-10 | 1496834 |
296K | 116 | 1.355 | 1584 | 997.657 | 3.99E-10 | 1580289 |
297K | 116 | 1.356 | 1480 | 997.415 | 4.58E-10 | 1476174 |
298K | 116 | 1.356 | 1496 | 997.163 | 4.48E-10 | 1491756 |
299K | 116 | 1.356 | 1480 | 996.902 | 4.58E-10 | 1475415 |
300K | 116 | 1.355 | 1573.33 | 996.631 | 4.05E-10 | 1568029 |
303K | 116 | 1.358 | 1460 | 995.765 | 4.71E-10 | 1453817 |
Table 3
Observations for Distilled Water
Temperature | TDS | Refractive Index | UV Ultrasonic Velocity (v) (m/s) | Density (ρ) (kg/m3) | Adiabatic Compressibility (β) (m2/N) | Acoustic Impedance (Ry) |
283K | 06 | 1.36 | 1500 | 999.757 | 4.4455E-10 | 1499635.5 |
284K | 06 | 1.36 | 1416 | 999.662 | 4.9891E-10 | 1415521.39 |
285K | 06 | 1.36 | 1480 | 999.554 | 4.5674E-10 | 1479339.92 |
286K | 06 | 1.36 | 1500 | 999.434 | 4.447E-10 | 1499151 |
287K | 06 | 1.36 | 1840 | 999.301 | 2.9558E-10 | 1838713.84 |
293K | 06 | 1.36 | 1488 | 998.261 | 4.5243E-10 | 1485412.37 |
296K | 06 | 1.36 | 1480 | 997.596 | 4.5764E-10 | 1476442.08 |
298K | 06 | 1.413 | 1500 | 997.102 | 4.4574E-10 | 1495653 |
299K | 06 | 1.413 | 1666.66 | 996.841 | 3.6114E-10 | 1661395.02 |
303K | 06 | 1.423 | 1613.33 | 995.706 | 3.8585E-10 | 1606402.36 |
Density depends on mass and volume, [18–19] temperature variations lead to changes in molecular associations, resulting in changes in mass and volume and hence density as shown in the Tables 1, 2 and 3. Under a set of experimental conditions the values of the three water samples, are affected by Total Dissolve Salts, Temperature .The regression and ANOVA statistics for Tap Water (highest TDS) and Adiabatic Compressibility are reported in Tables 4 and 5.Good correlation was observed in TDS and adiabatic compressibility of Tap Water.
Variation of adiabatic compressibility with temperature plotted for the three water samples, Tap Water, RO water and Distilled water have been shown in Figs. 1, 2 and 3 along with the trendline (dotted).
Figure 1, shows plot between adiabatic compressibility along with variation in temperature for tap water (TDS = 1060). The trendline line shows a uniform decline with temperature.
Figure 2 shows variation of adiabatic compressibility with variation in temperature for RO water carrying a TDS of 74. In temperature range (291 K – 294K) the graph shows a dip, while in the rest of the temperature range, the compressibility is constant. Trendline also shows a constancy throughout.
Figure 3 shows variation of adiabatic compressibility with variation in temperature for distilled water carrying a TDS of 06. A sharp dip was observed in the graph at 287K, while the trendline followed a pattern of minor decline.
3.1 Multiple Regression Analysis in Excel
While doing analysis with regression analysis [20] TDS was taken as independent variable and adiabatic compressibility as the dependent variable, regression analysis was performed for all the three samples, out of which positive correlation was found for tap water only while the other samples RO and distilled showed negative correlation.
Regression Statistics
Regression Statistics was applied to find the relation between adiabatic compressibility and TDS (Total Dissolved Salts) of the three water samples. The regression statistics for all three water samples (Tap water, RO water and Distilled Water) where temperature was taken as independent variable and adiabatic compressibility was taken as dependent variable showed very poor correlation. The correlation coefficient R, which measures the strength between the two variables (temperature and adiabatic compressibility) was found to be very poor 23% for Tap Water, approximately 0% for RO water, and 8% for distilled water.
Also, the F value (significance F), which states that if F value is less than 0.05 (5%) then model is acceptable. For all the three water samples F value was greater than 0.05 (0.26 for tap Water, 0.77 for RO water, 0.44 for distilled water, hence rejecting the possibility of correlation between temperature and adiabatic compressibility.
Regression Statistics yielded positive result for correlation between TDS and adiabatic compressibility for tap water. The correlation coefficient R was found to be 0.61(61%) and the F value (significance F) was found to be 0.034 (less than 0.05), this model finally passes the statistical test and comes under category of being acceptable.
Table 4
Regression Statistics between Tap Water and Adiabatic Compressibility
Regression Statistics |
Multiple R | 0.790675128 |
R Square | 0.625167158 |
Adjusted R Square | 0.55020059 |
Standard Error | 0.165222699 |
Observations | 7 |
The R-squared value of 62, indicates that our model accounts for 62% of the dependent variable’s variance. Usually, higher R-squared values are better. F value which shows that whether the model is acceptable or not (value should be less than 0.05), also passes the test of acceptability.
The standard error which shows how certain one can be of result, smaller the number, more certain one can be of result is 0.16, showing that the result comes in the range of being acceptable (smaller the number the more certain one can be of result).
Table 5
ANOVA Statistics for Tap Water and Adiabatic Compressibility
| Df | SS | MS | F | Significance F | df |
Regression | 1 | 0.227650155 | 0.227650155 | 8.339279392 | 0.034275401 | Regression |
Residual | 5 | 0.136492702 | 0.02729854 | | | Residual |
Total | 6 | 0.364142857 | | | | Total |
In the ANOVA Table 5, for Tap water the F- test for overall significance, significance F is 0.03 (< 0.05) which shows that the model is acceptable.
Our p-value for the overall F-test is 8.33783E-09. Value being small is written in scientific notation. The E-09, indicates that we need to move the decimal point 09 places to the left. Hence, can conclude that our regression model as a whole is statistically significant.
We included variables in our model: TDS and Adiabatic Compressibility. The coefficient is approximately 4.64. The positive sign indicates that as TDS increases, adiabatic compressibility also tends to increase. There is a positive association between these two variables. For every one-unit increase in TDS, compressibility increases by an average of 4.64.