weiming1998

Electrolysis of salt is an extremely inefficient (but cheap) way of producing chlorine. It is slow, it requires a salt bridge, and graphite/platinum anodes are needed to prevent corrosion and loss of yield due to the chlorine reacting with the anode. There are so many very easy ways to produce chlorine gas. Combining bleach solution (NaClO/NaCl) or bleaching powder/pool chlorine (Ca(ClO)2/CaCl2) and a (relatively) strong acid (sulfuric, phosphoric, oxalic, etc) will produce chlorine, since the strong acid will make a mix of hypochlorous acid and hydrochloric acid on site, which will react with each other, forming chlorine. Using hydrochloric acid directly is fine too (in fact, the reaction would be faster). Another method of producing chlorine is reacting chlorine tablets (trichloroisocyanuric acid, TCCA for short) with hydrochloric acid, or similarly with a chloride salt and a strong acid. Reacting HCl with a strong oxidizing agent like KMnO4 or MnO2 will produce chlorine as well. Reacting H2O2 and HCl will not produce Cl2 in appreciable quantities, though, due to the inability of H2O2 to directly oxidize HCl to HClO, since hypochlorites react with H2O2 in a comproportionation to form a chloride and oxygen. In my opinion, if you want to make chlorine gas for chemical synthesis, not just as a curiosity, it's definitely worth it to get the chemicals and make it chemically instead of electrolytically.

Firstly, Benedict's reagent doesn't require non-aqueous chemicals. Reacting a known amount citric acid and sodium bicarbonate in stoichiometric quantities will give you sodium citrate in aqueous solution, which you can easily calculate the amount made. Secondly, as I have made Benedict's reagent numerous times, I found that the quantities of chemicals used don't need to be precise. Simply adding excess carbonate solution to citric acid solution, then adding in a bit of copper sulfate made a blue solution that turned brown in the presence of glucose. Finally, apart from iron contamination, the brown-yellow colour can also be partial decomposition of sodium citrate under heat, as organics are very prone to decomposing to a yellowish-brown liquid.