Kidney stones are a painful and dangerous urinary disorder that could cause severe cramping, block flow of urine, and sometimes cause a fever that “about 5 % of American women and 12 % of men suffer from at some point in their lives” (Kidney Stone Disease). “Most small stones measuring less than 5mm or 6mm can persist in the body with medical expulsive therapy, will typically pass within a few days to a few weeks” (Kidney Stones Overview). Kidney stones are also referred to as renal calculi and are formed in the kidney as a result of buildup of minerals that are being excreted from the body as waste. This buildup can be caused by supersaturation which is when there is too high of a concentration of salts and proteins and this makes the metals precipitate into solid form within the kidney. Kidney stones are not all the same chemically, as shown in figure 2, Calcium stones are probably the most common stone which can combine to make Calcium Oxalate (CaC2O4), Calcium Phosphate (Ca3(PO4)2), Uric Acid (C5H4N4O3), Struvite (NH4MgPO4).
Figure 2. Frequency of Kidney Stones. Data from “Kidney Stone Disease.”
The fact that there are differing chemicals that make up kidney stones presents the problem of solubility in which some may dissolve in acidic solutions or may not dissolve at all. The kidney stones persist in the body due to the fact that the previously mentioned compounds are insoluble in water. This requires unusual tactics to rid the patient of kidney stones such as lithotripsy in which shock waves are used to break up kidney stones into much smaller pieces that can more easily be passed. Some home remedies are accredited with being able to dissolve the kidney stones in the kidney and being quite effective as well. In this experiment lemon juice is used in an attempt to dissolve a few of the most common kidney stones because of its high citric acid content. Perhaps the best treatment for kidney stones is prevention. In this case one would drink large amounts of water and be careful of too much salt and protein intake.
The experiment conducted involved such scientific concepts such as Ksp, percent yield, and percent error. Ksp is a scientific concept in which the solubility of a compound into water at 25 oC is quantified into a number which can be calculated and analyzed. Percent yield is a procedure which indicates how fully a reaction took place by comparing the actual mass attained with the theoretical value that should be attained assuming a complete reaction with perfectly standard conditions. Percent error shows the difference in the final experimental value with an accepted theoretical value which shows how accurate the experiment was which can show if the experiment is credible or not.
Kidney stones needed to be synthesized in order to carry out the experiment. Figure 3. Kidney Stone Formations
Calcium Oxalate: CaCl2 + Na2C2O4 2NaCl + CaC2O4
Struvite: MgCl2 + NH4NO3 + Na2HPO4 NH4MgPO4 +2Cl- + NO3- + 2Na+ + H+ Calcium Phosphate: 2Na3PO4 + 3CaCl2 6NaCl + Ca3(PO4)2
The reactions in Figure 3 were carried out in attempts of producing 5.00 g samples of each of the three stones. To do so, it was required to find the limiting reactant in order to calculate the appropriate amount of each substance to use. Below can be seen the calculations of how to find the limiting reactant for the reaction yielding calcium Oxalate.
Figure 4. Finding amounts of materials to use
Calcium Oxalate (CaC2O4)
Calcium Cloride (CaCl2)
Sodium Oxalate (Na2C2O4)
As can be seen in Figure 4, the first step is to find how many moles of CaC2O4 are in 5.00 g of the substance, then the number of moles is multiplied by the molecular weights of each of the reactants because the reaction is 1:1:1 with respect to the included compounds. This shows how much of each reactants to get in order to get our optimal amount of substance without much waste. However, the percent yield of each substance was quite low, as can be seen in Figure 5 and the calculations that lead to finding percent yield are as follows for the reaction yielding Calcium Oxalate, keeping in mind that 5.00 g is the desired dry mass.
Example Calculation: Calcium Oxalate (CaC2O4):
Figure 5. Percent Yield of Precipitates
Once the stones were collected, thoroughly dried, and massed, 0.100 g of the Calcium Oxalate was placed into an Erlenmeyer flask and dissolved in the home remedy: lemon juice. The stone readily dissolved into 10 mL of lemon juice to the point that no precipitate could be seen. 30 drops of ammonia buffer solution was added to raise the pH of the system to 10. At this point, 8 drops of indicator (Eriochrome black T) was added to the solution. .05 M EDTA solution was then added to a urette above a waste beaker and the EDTA was run through the burette until there was no air bubble in the burette.
Then the first reading was taken off of the burette before the titration started and then the EDTA solution was carefully added to the experimental solution in the Erlenmeyer flask below. This was done for a total of 3 trials, however, only for the Calcium Oxalate stone because of time constraints and material constraints. Figure 6 displays the data that was collected during this process. Figure 6. Data from Titrating CaC2O4 solution
With use of Figure 6, the amount of EDTA that must be added to 0.10 g of CaC2O4 can be averaged to 53.2 mL of .05 M EDTA (H2Y2-).
Figure 7. Finding percent dissolved of Calcium Oxalate
Ca2+ + H2Y2- CaY2- + 2H+ *Notice Ca2+:H2Y2-= 1:1 (Complexometric Ca Determination)
Amount of CaC2O4 dissolved:
In Figure 7, it is determined that 335 % of the Calcium Oxalate kidney stone dissociated in the lemon juice by first finding how many moles of EDTA were used by multiplying the molarity of the EDTA by the average amount of EDTA used to titrate the experimental solution. The equation for the reaction between a free calcium ion and an EDTA compound in pH of 10 is a 1:1 reaction which allows to see how many calcium ions were stabilized and therefore dissociated from the CaC2O4. This number of moles can then be multiplied by the molecular mass of CaC2O4 to find the initial weight of the ions that dissociated which comes to be .335 g of CaC2O4.
This mass is then divided by the amount that was in solution which was 0.10 g, then multiplied by 100 to give a final percent of dissociation for the CaC2O4 in lemon juice of 335 %. This means that the kidney stones dissolved into 3.35 times the amount of ions than it could possibly, suggesting quite large errors in the experiment/procedures occurred. Figure 8. Finding Ksp for the dissociation of Calcium Oxalate Concentration of Ca2+:
Ksp for the titration: [Ca2+] [C2O42-]
Ksp= (0.2377)2 = 0.0565 *Theoretical Ksp= 2.3210-9 (Tro, Chemistry, A-12)
The calculations in Figure 8 show the steps needed to find the Ksp for the dissociation of CaC2O4. The concentration of Ca2+ ions within the solution and buffer solution (10 mL of solvent and 1 mL of buffer) was found by dividing the number of moles found in Figure 7 by the amount of solution present. The Ksp for this particular reaction can be found to be a 1:1 ration between the Ca2+ ion and the C2O42- ion which allows for simple squaring of the concentration of the Ca2+ ion to give the experimental Ksp. However, when compared to the theoretical value of Ksp for the dissociation of CaC2O4 at 25 oC, the experimental value obtained is shown to be largely incorrect with a percent error of 2.435×1011.
The data that shows a 335% dissociation and an overall percent error of 2.435×1011 of CaC2O4 which means that the kidney stones dissolved into 3.35 times the amount of ions than it could possibly, suggesting quite large errors in the experiment/procedures which were probably caused by the conflict between the yellow color of the lemon juice and the indicator which is supposed to turn blue, however, the solution turned green very gradually which must have led to the incorrect results. If the experiment had not had such large errors, the experiment would have shown whether or not lemon juice could dissolve kidney stones effectively or not.
Perhaps the lemon juice had dissolved the Calcium Oxalate more effectively than water at standard conditions which could have contributed to the large error because the error states the Calcium Oxalate dissociated much more than expected which would favor the possibility that the lemon juice is a much better solvent than water. However, further tests would be needed to be conducted to confirm this theory.
Kidney stones are a harmful and sometimes dangerous renal condition in which a compound that is insoluble in water gets trapped in the kidney and can be very difficult to expel. This led to the investigation of whether home remedies can help with kidney stones by dissolving them. However, the decision to use lemon juice in the experiment was flawed and therefore the results cannot be used for scientific data collection. The mistake of mixing the colored lemon juice and the indicator ultimately skewed the results incomprehensively because a definite titration point where the solution was just equalized could not be found. Subsequently, the lemon juice may have helped dissolve the kidney stones, however, it cannot be confidently determined from this experiment.
Fredric L. Coe, Andrew Evan and Elaine Worcester, “Kidney Stone Disease,” American Society for Clinical Investigation 115 (2005): 2598–2608, accessed October 5, 2014, doi: 10.1172/JCI26662 “Kidney Stones Overview,” Washington University School of Medicine in St. Louis, accessed October 5,
Remik44992. “Couple of kidney stones on macro shot.”
http://www.shutterstock.com/pic- 91980854/stock-photo-couple-of-kidney-stones-on-macro-shot.html?src=6DK-IP65Yj0z5jaeXvYdSw-1-1. “Complexometric Ca Determination,” Ulrich de la Camp and Oliver Seely, accessed October 20, 2014, http://www.csudh.edu/oliver/che230/labmanual/calcium.htm.
Tro, Nivaldo J. Chemistry: A Molecular Approach. (New Jersey: Pearson Education, inc. 2014), A-11-A-12.