.40g of NaH_2PO_4, and .40g of Na_2HPO_4 was measured into a 150 mL beaker. 50mL of distilled water was then measured in to a graduated cylinder and added to the 150ml solution of NaH_2PO_4 and Na_2HPO_4. 20 drops of the .04% Bromothymol blue solution was then also added to the buffer solution. After adding the 20 drops the tint of the liquid changed to a light green. The Vernier pH probe was calibrated and used to determine the pH of the phosphate buffer solution which was 6.81.
After sitting for 30minutes this solution stayed the same color. Table 2: Solution Colors Before 30 Minutes of Sitting in a Beaker of Water and After Benedict’s test Solution Content | Initial color | Final color | 15% glucose1% starch | Cloudy | Orange | Distilled water | Clear | Blue | This table shows the colors of the solutions before sitting for 30minutes in the solution of water and IKI and the final color after the Benedict’s test has been performed on the solution. The initial color of the 15% glucose and the 1% starch before sitting in the beaker solution for 30 minutes and before the Benedict’s test was perform was a cloudy white color. After the Benedict’s test was performed on this solution it turned an orange color. The solution in the beaker which was distilled water was clear before the IKI was added and before the dialysis tubing was placed in it.
25 ml of diluted unknown acid solution to 100ml beaker by using 25 volumetric pipet. 10ml of deionized water and 3 drops of phenlpthalin indicator the beaker labeled as 3. Potentiometric titration acid solutions 125 ml of NaOH was obtaining in a beaker and 50 ml of NaOH transfer to buret the tip and the meniscus is at below 0 ml. one magnetic stirring bar placed in a beaker contain one of the known solution on a stir. The pH recorded by using pH electrode before adding NaOH.
Materials and Methods To first create the three distinct solutions, 50mL of phosphate buffer with a pH of 6.84 was poured into a 150mL beaker with 20 drops of 0.04% Bromothymol blue indicator. 5mL of the solution was then added to three separate 50mL beakers. 1mL of HCl was added to one of the three beakers and labeled ‘Yellow’, 1mL of NaOH was added to another and labeled ‘Blue’, and 1mL of distilled water was added to the last beaker and called ‘Green’. The spectrometer was prepared and left to warm up before calibrating it. Taking the three solutions prepared earlier, each was transferred to three separate cuvette while filling the fourth cuvette was filled with distilled water.
After the mixture was heated, there was solid on the bottom and liquid on the top of the flask. The set up was let cool to room temperature. Next, we decanted the mixture in to a clean 100 ml beaker. We rinsed the remaining solid with 10 ml of DCM and swirled the mixture. The mixture was decanted again in to the same beaker.
Once the solution of sodium thiosulfate had been standardized the molarity of the solution was known and sodium thiosulfate could be used to titrate tap water and an iodine solution to determine the amount of chlorine in the tap water and iodine in the iodine solution. Procedure/ Observations: The first step of the experiment was to standardize the sodium thiosulfate solution. This was done by cleaning a 50 mL buret and rinsing it three times with sodium thiosulfate solution to ensure the surface of the buret was consistent with the sodium thiosulfate throughout. The buret was then filled with the sodium thiosulfate solution. The buret was monitored to ensure that the solution extended to the tip of the buret and that no air bubbles were present because both would cause an inaccurate titration.
This was allowed to cool to approximately 55ºC and ethidium bromide (10mg ml⁻¹) was added to a final concentration of 0.5 μg ml⁻¹. 4. The gel was poured to a depth of about 5 mm, taking care to avoid bubbles and was allowed to solidify for 30 mins at room temperature. 5. The tape was removed and the trough containing the
After which time, 2.1 mL of 30% hydrogen peroxide was added slowly followed by sodium hydroxide until a pH of 8 was observed. 20 mL of H20 and 10 mL diethyl ether were added to the flask. The contents were separated and the aqueous layer was rinsed with four 10mL portions of ether followed by 15 mL of sodium bicarbonate. The ether layer was dried with granular magnesium sulfate and then the solvent was removed by evaporation under reduced pressure. Lastly, the final product was analyzed by mass spectrometry and HNMR.