Which Citrus Fruits Remove Stains The Best Environmental Sciences Essay

Nowadays, most of people prefer to use biodegradable product or “green” product. Especially in current downturn economy, many people change to less expensive products. Using citrus fruits as an alternative ways to remove stain is the good choice. Is it very useful to know which of the citrus fruits is best used in removing stains?

Significance of the Study

Sodium hypochlorite (chlorine bleach) and hydrogen peroxide (oxygen bleach) are extremely popular in the market to whiten the fabrics. However, there are some disadvantages using oxygen and chlorine bleaches. Most of them are hazardous if ingested or inhaled and should be used with care. Lindsay Evans (2009) also explained the chlorine can cause negative health effects. Besides, they are costly and give a bad impact to our environment especially rivers and lakes ecosystem. Chlorine that flowing into rivers or lakes will combine with other chemical to form a stable compound where it will remain unchanged in groundwater for many years (Wisconsin, 2010). On the other hand, citric acid best uses as natural bleaches because it does less harm to ecology of rivers and lake.

Limitation of the study

All of the experiment will conduct in the Mara College Seremban’s laboratory. Most of the material such as citrus fruits; lemon, lime, navel oranges and pineapple and table salt are obtained from Carrefour Cheras in Cheras, Selangor, Malaysia. So, all of the fruits are not in the same level of freshness due to different condition during storage that may affect the freshness of the fruits. Besides that, the fruits might not come from same tree and this will affect the concentration of acid in the fruits.

Research Question

The focus of study is to investigate the ability of citrus fruits as natural bleach to remove stain from fabric. The main objective of this study is to identify which of the citrus fruits; lime, lemon, pineapple, and navel oranges is best used as bleaching agent.

So the research question of the study is “How does the type of citrus fruits used affect the rate of reaction of stain removable with influence of sodium chloride?”

The study uses 4 different types of citrus fruits which are lime, lemon, pineapple, and navel oranges that will extract into juice and add with table salt (sodium chloride).


The research question of the study is “How does the type of citrus fruits used affect the rate of reaction of citric acid to remove stain from fabric with influence of sodium chloride?” The rate of reaction of citric acid is the highest at the most acidic solution.So the hypothesis is the most acidic fruit in this case is lime or lemon as both contains high concentration of citric acid.


Independent Variable

The independent variable is the different types of citrus fruit juices. The citrus fruit juices that will use are lemon, navel orange, lime and pineapple.

Dependent Variable

Rate of reaction to remove the stain from fabric will be the dependent variable. The time taken will be record by stopwatch for the stain to decolorize. Then use formula to calculate the rate of reaction.

Fixed Variable

The fixed variables are type of cloth (cotton), volume of juice (5oml), temperature (100Ëšc) and volume (100ml) of water bath, quantity of sodium hydroxide (3 teaspoon) and type of stained( syrup solution). All of this material will be use in same quantity throughout of the experiment.

4.0) Procedure and Analysis

Preparation of an approximately 0.1 M Sodium Hydroxide Solution followed by the Standardization of the Sodium Hydroxide

Before testing the concentration of citric acid, the standard sodium hydroxide solution needs to be prepared. In order to prepare 0.1 M of NaOH, 9.0 cm3 of 1.0M sodium hydroxide solution was diluted with 100.00cm3 of distilled water. Then the sodium hydroxide solution was standardizing to determine its concentration by titrated it with KHP. This acid base reaction is shown in Equation 1(M.L.Gillette,1999);

KHP(aq) + NaOH (aq) NaKP(aq) + H2O(l)………………………………(eq1)

Two portion of 0.5g of dried potassium hydrogen phthalate (KHP) was weighed and dissolved with 50ml distilled water in conical flask. The Phenolphthalein solution was added for 2-3 drops into KHP solution to indicate the end point of titration. Phenolphthalein is used because the product’s pH range between .The sodium hydroxide was titrated with KHP solution until pale pink color was produced. The volume of NaOH solution added was recorded.

Extraction of juices from citrus fruits.

The lemon was cut into small pieces and blend with blender. The juice released was putted into the beaker and labeled with A. First step was repeated again until half of the beaker filled. Then, the extracted juice was filtered through muslin cloth. The whole procedure were used again with another type of fruits, lime, navel orange and pineapple and labeled with;

Citric acid Determination

The concentration of citric acid is determined by titrate the fruit juices with NaOH. The approximately 10 mL of lime juice be prepared by using pipette and was transferred into a conical flask. Then, the lime juice was diluted with 20ml of distilled water and three drops of phenolphthalein was added into solution. The solution with 0.1M sodium hydroxide (NaOH) was added from burette to the juice sample while swirling the mixture until the reaction mixture turned into faint pink color. The end point was reached when the pink color persists for thirty seconds. The volume of NaOH added was recorded. The processes were repeated again to increase the accuracy. Then, the procedure was used again with different type of juice; lemon, orange and pineapple. By using the formula, the molarity of citric acid in the fruit juice was calculated.

Qualitative Data

The colour of solution in conical flask change from white colour to faint pink colour.

Data Analysis- calculation for determining the citric acid concentration through sodium hydroxide added.

The citric fruits consist of citric acid. Citric acid contains carboxyl acid group and reacts with hydroxide ion as indicate in equation 2 (Dr. Ewa &Thomas, 2007). The sodium hydroxide will ionize to form sodium ions and hydroxide ions (eq 1).

NaOH (s) Na+ (aq) + OH – (aq) (eq 1)

C3H5O (COOH)3 (aq) + 3 OH- (aq) C3H5O(COO)33- (aq) + 3 H2O (l) (eq 2)

The purpose of this experiment is to determine the concentration of citric acid on the citrus fruit by titrating the citrus juice with standard sodium hydroxide solution. The concentration of citric acid can be calculated by measuring the volume of sodium hydroxide used (eq 3).

Molarity,M= (eq 3)

M1V1 = M2V2 (eq 4)

Based on the equation, the molarity of the OH- ions equal with sodium hydroxide as the molecular ratio is 1:1. So, the molarity of hydroxide ions can be known. By using equation 4, the concentration of citric acid can be determined.

Calculating the concentration of citric acid

By using the data given above, I had calculated the concentration of citric acid in citrus juices. The citric acid C6H8O7 is a triple basic acid that consists of three carboxylic acids and react with one hydroxide ion ,eq 1(Ewa Peter & Thomas M Moffet, 2007). In this experiment, I assumed that the citric acid is sole acid found in the citrus fruits.

C3H5O(COOH)3 (aq) + 3 OH- (aq) C3H5O(COO)3 (aq) + 3 H2O (l)……………….(eq 1)

However, according to experiment conducted by Law.C& Solak.E(2009) the citric acid does not always have the 3 carboxylic acid. So, in this experiment I will assume that the citric acids only have 1 carboxylic acids but it’s less accurate. The following reaction takes place in the titration;

C6H8O7 + OH- → H2O + C6H7O7-………………… (eq 2)

Based on the equation(eq 2), the molarity of the OH- ions equal with C6H8O7 as the molecular ratio is 1:1. By using equation below, the concentration of citric acid can be determined.

M1V1 = M2V2

where :

m1 = molarity of Sodium hydroxide, NaOH

v1 = volume of Sodium hydroxide Solution, NaOH

m2 = molarity of dilute citric acids, C6H8O7

v2 = volume of dilute citric acids Solution, C6H8O7

Procedure for process of stain removable

The white cloth cotton was cut into3cmÃ-3cm size for 20 pieces and each pieces of cloth were stained with syrup solution. Then the stained clothes were dried for about 1 hour. 20 cm3 of lime juice was prepared and the initial pH of juice was recorded by using pH meter. For the first trial, a stained cloth was held under the running water and was soaked in the lime solution for more than 30 minutes (diagram 4.1). After that, the stained cloth was put into100Ëšc hot water bath and the time taken for the stained decolorize was recorded. However, the stained took longer time to decolorize where the results recorded were inaccurate. So I used another method by adding 3 teaspoon of table salt (sodium chloride) into lime juice. The pH value of juice was recorded. The stained cloth was rubbed with salt before soaked into the solution for an hour. Then, the stained cloth was putted into 100°C hot water bath and the time taken for the stained decolorized was recorded. In order to identify the best fruit best use to remove the stain, the whole step was repeated again with another type of fruits; lemon, navel orange, and pineapple. The results from different type of fruits were compared.

Besides that, I also used the different type of stain to test which one is more effective been bleached by citric acid. In this experiment I used vegetable based stain which is tomato stain. The first method is used; without adding the table salt (sodium chloride) and the result was recorded and be compared with synthetic stain (syrup).

Qualitative data

For synthetic stain:

The pink’s colour of stain turns into colourless.

Fabrics become white

Fabric cloths smell fruity.

The juices become more slippery when added with sodium chloride.

For organic stain

The brown colour of mud decolorize

The fabric colour turn into brownish

The fabric become smelly

The juices become more slippery when added with sodium chloride.

Data Analysis

According to the data collected, the different type of fruits and different type of stain will affect the time taken for the stain to decolorize. For the syrup stain, there must be influenced by sodium chloride (cooking salt) as it is hard to remove by citric acid alone. Adding the cooking salt involved the osmosis concept where when the solution become more saturated, the water will moving from the cloth to the salt and taking the stain together. When the cooking salt is added into the juice, the pH of juices drop and become more acidic. However, chemically the cooking salt does not affect the acidity of citric acid. The drop in pH value may be due the presence of water in the juices which react with the salt and release the hydrogen ions which might cause this to be happened

8.0: Conclusion and Evaluation

8.1- Conclusion

Based on the results of the experiments carried out in this essay, its show that the type of citrus fruits used does affect the average time taken to remove the stain. The hypothesis that average time taken would be fastest in the most acidic fruit (lime) which consist high concentration of citric acid, is also supported based on the data collected.

The main objective of this essay is to identify which of the type of citrus fruits; lime, lemon, pineapple, and navel oranges are best used as bleaching agent. As mention above, the type of citrus fruit does affect the average time taken to remove the stain. However, it also depends on the type of stain. Test on fabric with synthetic stain without adding sodium chloride (salt) required a long time where the average time taken cannot be collected. Meanwhile, citrus fruits are best used on fabric with vegetable based stain as there in no influence with sodium chloride. In addition, the time taken to remove the stain for vegetable based stain is fastest compare than synthetic stain. Besides that, the citrus fruit only react as bleaching agent in hot temperature only. It is possible that the stain can be removed under room temperature. Thus it can be concluded that, the lime is the best used as bleaching agent but with certain condition; type of stain and temperature.

8.2- Evaluation

Some error and limitation occurring during the experiment which causes the result collected imprecise. The limitation and errors in these experiments can be divided into several parts. For the first part is problem in procedure A. Initially, the sodium hydroxide prepared had been assumed exactly 1.00M. However, to test the accuracy of the concentration, the sodium hydroxide had been standardized using KHP solution. After calculating the concentration of the sodium hydroxide, the concentration of sodium hydroxide is approximately 0.1M with 0.2% of percentage error.

There is a limitation occur when calculating the concentration of citric acid by titrate it with sodium hydroxide solution. One problem is the assumption that the citric acid is the sole acid in citrus fruits. The citric acid should been standardized to know the exact concentration. Besides that, some common mistake occurred in the experiment such as improper position of burette and parallax error in taking the measurement. To overcome this, there is no other solution except reduce the parallax error by positioning the eyes straight to the scale reading needed and position the apparatus used at the smooth surface. Moreover, it was hard to determine that the colour of the solution turned to faint pink colour because if the titration of NaOH was titrated without care the solution will become too red. So the result of the first faint pink colour come out should be observed and detected properly so it needs a particular partner in doing that job.

In the last part(procedure D), most of error occurs is during taking the average time taken to remove the stain from fabric. When the stained fabric is place into hot water, it is difficult to identify whether the cloth decolorize or not because it is possible for fabric to turn into white without be rub. To improve this, the experiment must be repeated for several times to increase the accuracy. There is also a limitation where the removable of stain cannot be seen clearly when test conducted with coffee at first. So, to overcome this problem, the stain was changed into syrup which the red colour can be seen clearly.

8.9: Recommendation for further research

More work could be done on the use of sodium chloride (cooking salt) in removing stain, is it effective used and how it will increase the effectiveness of citric acid in removing stain. The effectiveness of citric acid should be compared with commercial bleach and color safer bleach. Which one is best used? Besides that, the uses of citric acid can be extending more into the cleaning process; such as kitchen utensils and rusting. The investigation should be carried on how does cold water remove stains? The method of soaking cloth with cold water to remove stain is quite effective and the chemistry behind this should be expose.