Title : Determination of Chloride in Urine in Different Circumstances
To determine the chloride content by titrating mixtures of urine against potassium thiocyanate under in different circumstances.
How do different conditions of urine samples collected affect its concentration of chloride which is measured by titrating the mixture of urine with potassium thiocyanate until it turns red?
The greater the consumption of food, the higher the chloride concentration in urine. This can be investigated by varying the time when the urine sample is taken. One urine sample is taken before meal, one after meal and the third sample should be after a high consumption of water. The lesser the volume of the potassium thiocyanate needed to turn the mixture of urine sample to red, the higher the amount of chloride content in the urine.
Variable| Unit| Methods of controlling|
Independent:Conditions when urine sample is taken| | The urine samples are taken at the specified times and conditions; before meal, after meal and after a high consumption of water.| Dependent :Volume of potassium thiocyanate needed to turn the urine mixture red. | Cm3| Record the volume of potassium thiocyanate needed to turn the urine mixtures red using the process of titration.|
Variable| Unit| Methods of controlling| Possible effects on results| Constant: Volume of urine and silver nitrate solution| cm3| Use 2cm3 of urine for each sample and 10cm3 of silver nitrate solution for every trial.| If different volumes of urine sample and silver nitrate solution are used, the concentration of the mixture will be different and this will affect the end result of the experiment.| Concentration of potassium thiocyanate and silver nitrate| M| 0.1 M of potassium thiocyanate and silver nitrate are used.| A higher concentration will increase the rate of reaction and this will affect the outcome of the results. Each trial should be consistent.| Time for the mixture to be stirred| min| The mixture is to be stirred for 5 minutes each trial.| The mixture has to be stirred according to the given time so that the silver nitrate will react completely with the urine sample.|
Urine| Trial| Burette reading of potassium thiocyanate / cm3 (± 0.05cm3)| Amount of potassium thiocyanate used / cm3 (±0.10cm3)| | | Initial| Final| |
Fasting| 1| 0.00| 2.10| 2.10|
| 2| 10.50| 12.40| 1.90|
| 3| 12.40| 14.00| 1.60|
Fed | 1| 6.00| 8.30| 2.30|
| 2| 14.00| 16.40| 2.40|
| 3| 18.20| 20.00| 1.80|
Watered| 1| 8.30| 10.50| 2.20|
| 2| 20.00| 22.00| 2.00|
| 3| 22.00| 24.50| 2.50|
Table 1: The condition of urine sample and the initial and final burette containing potassium thiocyanate to turn the initial urine colour to red
1. The initial colour of the urine samples are yellow and pale yellow. 2. The colours of urine mixtures change to red after titrated with potassium thiocyanate. 3. The colour of urine mixture turns darker red if potassium thiocyanate is continuously added.
Calculating the average volume of potassium thiocyanate used to turn mixture of urine sample from its initial colour to standard red:
Trial 1 + Trial 2 + Trial 3 3
Example using student A’s fasting level urine sample:
2.10 + 1.90 +1.603 = 1.87 cm3
Calculating the standard deviation:
Calculating the standard deviation of average volume of lime juice needed to decolourise the DCPIP solution by using GDC: 1. Press (STAT) button
2. Press number 1 on the GDC
3. Insert the data (for trial 1, 2,3) in the column that appear on the GDC’s screen, we may choose to insert the data in the L1, L2 or L3 column. 4. Press the ENTER button to insert the data in the column. 5. Then, press the (STAT) button again.