CHLORINE 1
Running Head: CHLORINE 1
Determining the Free Chlorine Content of Swimming Pool Water
Student’s Name
Institutional Affiliation
Determining the Free Chlorine Content of Swimming Pool Water
Abstract
The study aimed at coming up with the ways by which the amount of chlorine in swimming pools can be determined. From the previous reviews, it was established that swimming pool water must have some amount of chlorine in it, though the amount should not be too much as it can pose some threats to people using the swimming pool. In this experiment, Colorimeter will be used to determine the content of chlorine in swimming pool water.
Introduction
In the nineteenth century, Physicians used chlorine water for killing bacteria (Richardson, DeMarini, Kogevinas, Fernandez, Marco, Lourencetti, … & Marcos, 2010). When it was discovered that some diseases are transmitted by water, municipalities started using chlorine to cleanse public water. It is the same reason as to why chlorine is added to swimming pools. Chlorine when in contact with water, a reaction occurs forming hypochlorous acid (HOCL) and a hypochlorite ion (OCL). The two, when in water is what is called free chlorine. (Richardson et al. 2010).
Method
Colorimeter method was used in the study to show the quantity of free chlorine in the water from a selected swimming pool. As the solution to be used in the experiment is red, the people experimenting were advised to apply the 565 nm (green) LED as stated by Dong, Li, Zhou, Wang, Chi, & Chen, (2012). We had to come up with the most suitable wavelength depending on how the absorption spectrum of the solution would be determined. We had to measure how light is absorbed by the aqueous solution which had a known concentration sample of chlorine by Beer s law. N, N-diethyl-p-phenylenediamine is reacted with the chlorine in each sample produced. After the reaction, the DPD will be oxidised, making a product known as magenta which is red. In the experiment, the standard solutions for free chlorine were prepared. The colorimeter was then used to determine the absorption rate of each standard sample. After that, a graph of concentration against the absorption of free chlorine was plotted. The level of free chlorine in the water was then determined from the chart, (Weng, Li, & Blatchley III, 2012).
The following are the reagents used in the experiment: 10 mg/l computer free chlorine standard on a Vernier interface of a computer, samples of water from a swimming pool, chlorine powder which is free of the DPD substance, Vernier Colorimeter, a pipet which is 25 ml in capacity, a cuvette, pipet tissues which are 10 ml capacity, pipet pumps, six beakers of 50 ml each, rods for stirring, and 100 ml beaker of distilled water.
Procedure
We had to obtain and wear some goggles, after which Six clean and dry beakers, 50 ml each were labelled as from 1-6. About 20 ml of the standard solution of free chlorine (10 mg/l) was transferred into the beaker which 100 ml in capacity. The 10 ml pipet was then used to extract exactly 1.00 ml of the prepared solution of the free chlorine into beaker one, after that, the 25 ml pipet was then used to add 1 ml of distilled water into the same beaker. The same procedure was then repeated to prepare the same solution in beakers 2 to 5.
With the prepared solution and the remaining distilled water, the 25 ml pipet was used to transfer the sample of swimming pool water into a beaker and then one DPD free-chlorine powder pillow was added to each of the beakers labelled initially. The powder was then well mixed into the selected water using the stirring rod. After stirring, a blank was made by pouring distilled water in an empty cuvette to about ¾ full and then closed with a lid. For accuracy, the cuvettes were wiped dry on the outside using a tissue paper. Furthermore, the solutions within the cuvettes were checked to be free of bubbles. After that, the cuvettes were positioned so that light could pass through the transparent sides.
The Colorimeter is connected to the computer interface. The machine is then prepared for the collection of data by opening the file selected for the free chlorine data. The Colorimeter lid was opened, the blank put into it and then closed. Moreover, the Colorimeter was calibrated and prepared to measure the developed solutions. The ‘less than’ or ‘greater than’ button on the Colorimeter is pressed to select the 565 nm wavelength which is for green. CAL button is pressed until the flashing of the red LED begins is when it is released. We waited until the LED stopped flashing, indicating that the calibration is complete, (Dong et al. 2012). The blank Cuvette was then emptied of water, and then rinsed twice with the solution in beaker one with 1 ml amounts, after which it was again filled to about ¾. The outside of the Cuvette was after that cleaned and inserted in the Colorimeter.
We were in a position to come up with data on absorption and concentration for all the solutions tested. The cuvette containing the solution from beaker one was left in the Colorimeter with the lid closed. After the stabilisation of the value displayed on the monitor after clicking b, we again clicked and entered 0.40 as our concentration in mg/l. After clicking again, the absorption and concentration value for the first solution was saved. The contents in the cuvette were then poured and the cuvette rinsed twice using 1ml amounts of the solution in beaker 2, and then it was filled again to about ¾. The cuvette was again placed in the Colorimeter. We waited for the value to stabilise before clicking. We entered 0.80 mg/l to be the concentration and clicked. The steps were then repeated for beaker 3 (1.2mg/l), the fourth beaker (1.6 mg/l) and the fifth beaker (2.0 mg/l). We finally waited until step 11 before measuring the absorption of the swimming pool water, that is in beaker six.
Results
We had to study the data pairs on the absorption against the concentration graph. On moving the examine line, the intake and concentration values of each data are shown on the right side of the graph. We noted down the absorption and transmittance data values in a table. The graph of absorbance against concentration was examined. To find out whether there was a correlation between the two variables, we had to press the linear fit button.
Discussion
With the curve of linear regression displayed on the graph, it is necessary to select interpolation from the analyse menu as argued by Weng (2012). A vertical cursor will automatically appear on the graph. The concentration and absorption of the cursor will be shown in the floating box. The cursor is to be adjusted within the line of regression until the value of absorption is almost the same as the one we noted as we were finalising the 11th step. The corresponding value of concentration is now the concentration of the free chlorine of the selected swimming pool sample in mg/l. The graph of absorption rate against the level of consistency is printed, together with the line of regression and the interpolated concentrations which are unknown. The cursor was moved up the vertical line of the cursor to the toolbar to keep the interpolated values of level displayed (Dong et al. 2012). The resultant graph and the table are as shown below:
Fig 1.0
In conclusion, the Colorimeter method is the best way of determining the content of free chlorine in swimming pool water. The technique will give you the direct relationship of both concentration and absorbance rates of the selected sample of the swimming pool. Furthermore, it will be easy for one to come up with a plotted graph for the comparison of the two variables. Moreover, the method works better when it comes to determining the safest swimming pool as far as the people’s health is considered.
References
Dong, Y., Li, G., Zhou, N., Wang, R., Chi, Y., & Chen, G. (2012). Graphene quantum dot as green and facile sensor for free chlorine in drinking water. Analytical Chemistry, 84(19), 8378-8382.
Richardson, S. D., DeMarini, D. M., Kogevinas, M., Fernandez, P., Marco, E., Lourencetti, C., … & Marcos, R. (2010). What’s in the pool? Comprehensive identification of disinfection by-products and assessment of mutagenicity of chlorinated and brominated swimming pool water. Environmental health perspectives, 118(11), 1523-1530.
Weng, S., Li, J., & Blatchley III, E. R. (2012). Effects of UV254 irradiation on residual chlorine and DBPs in chlorination of model organic-N precursors in swimming pools. Water Research, 46(8), 2674-2682.