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8., INVESTIGATORY PROJECTS, PROJECT, AIM, Checking the bacterial contamination in drinking water by testing sulphide ion., APPARATUS, Beaker, test tubes and test tube stand., REAGENT, Sodium nitroprusside solution., The drinking water is contaminated by bacteria. The bacterial contaminatin in potable water, is caused as a result of the mixing of sewerage water into it. Bacterial contamination is also, THEORY, noticed in river water as well as water obtained from lakes., The biotic compounds are oxidised by the aerobic and anaerobic (non-aerobic) bacteria, present in sewerage water. The products of oxidation caused by aerobic bacteria possess, bad smell. This process of oxidation of sewerage is known as aerobic oxidation because it, occurs in presence of oxygen., The anaerobic oxidation is caused due to lack of oxygen in polluted water. It is responsible, for putrefaction in it. It forms gases like methane (CH,), hydrogen sulphide (H,S), phosphine, (PH,) and ammonium sulphide [(NH,),S]. The smell of these gases is very bad. This process, of oxidation in presence of low content of oxygen is known as anaerobic oxidation., The sewerage water has bacteria in large number. The bacterial contamination is very, harmful. It can cause several diseases like dysentery, vomiting and cholera. Therefore, it 15, very important to test the drinking water for the presence of sulphide ions., 2-3 drops of sodium nitroprusside solution are added to a sample of potable water. If thee, is the development of violet coloration in it, it indicates the presence of sulphide ions due to, bacterial contamination in the given sample of water., PROCEDURE, (i) Collect water samples from different sources such as well, river, hand pump and pond. Mark these sapae, A, B, C and D., (i) Take 2-5 ml of each water sample in different test tubes., (ii) Add 1-2 drops of sodium nitroprusside solution to each test tube and shake., (iv) Record in the table the observations made., 76, CHAPTER

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OBSERVATIONS, Sr. No., Water sample, Colour developed, Bacterial Contamination, 1., Sample A, No colour, No. It is pure water., 2., Sample B, Violet colour, Yes. It is contaminated water., 3., Sample C, No colour, No. It does not contain sulphide ion., 4., Sample D, Violet colour, Yes. It contains sulphides ions, RESULT, Water samples B and D have sulphide ions. Therefore, they have bacterial contamination., VIVA-VOCE, formation of violet coloration confirms the presence of, Inhide ions in the given sample of the potable water.

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PROJECT, AIM, To investigate the foaming capacity of different washing soaps., Four 150 ml beakers, test tubes, test tube stands, tripod stand, wire gauze, 25 ml measure, cylinder, glass rod and stop watch., APPARATUS, Different samples of soap and distilled water., The foaming capacity of different washing soaps can easily be compared by noting the time, taken for the disappearance of foam formed by equal volumes of various samples with the, same force. Lesser the time taken by the foam of soap sample to disappear, the lower will be, its foaming capacity., CHEMICALS, THEORY, PROCEDURE, (i) Take four 150 ml beakers and label them as A, B, C and D., (ii) Weigh 1 g of each soap sample and put one sample in one beaker., (iii) Add 25 ml distilled water with measuring cylinder in each beaker., (iv) Dissolve the soap in water using a glass rod and by heating gently., (v) Place four test tubes marked as A, B, C and D in test tube stand., (vi) Pour 1 ml of soap solution already prepared in the test tube of corresponding number., (vii) Add 10 ml of distilled water with the measuring cylinder in each test tube., (viii) Pick up one test tube and shake its contents vigorously 5 times. Put it on the test tube stand and immediately, start the stop watch., (ix) Note the time taken for the disappearance of foam in the test tube., (x) In the same way, find out the time taken for disappearance of foam produced in test tubes B, C an, respectively shaking each test tube for equal number of times by the same force., OBSERVATIONS, Weight of each soap solution taken = . g, Volume of each soap solution = . ml, Volume of distilled water added to soap solution = ml, Number of times each test tube is shaken =, 82, PaicAL CUESTAY Cs

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Projects, Soap samples No., Time taken for disappearance of foam in seconds, A, C, INFERENCE, The soap sample for which time taken for the disappearance of foam is maximum has maximum foaming, capacity. Therefore, it is the best cleansing agent among the given samples., RESULT, Soap sample number.. has the maximum foaming capacity., PRECAUTIONS, 1. Weighing of soap of measuring volumes should be done accurately., 2. The same distilled water should be used for each sample., 3. Each test tube should be shaken in a similar way for equal number of times., 4. The time of disappearance of foam should be noted accurately.