The process of adding the proper amount of salt is one of the most challenging and risky tasks in cooking, despite how simple the motion itself may seem. No long justifications are necessary because even a small amount of excess salt in a meal runs the risk of ruining the flavour entirely. We have all had overly salty paneer or dal, but it is more likely to happen while making first courses and side dishes, where salt tends to dissolve more.
Numerous home cures have been developed that are intended to balance an overly salty food, and much has been spoken and written in scientific terms on how to fix the problem or at least to lessen it. Adding a potato to the dish, either whole or broken up into pieces, is one of the most popular remedies (depending on whoever is explaining the method, often backed up by pseudo-scientific notions worthy of a science fiction film). This idea holds that the potato absorbs the extra salt like a sponge, saving you from throwing away food that would otherwise be discarded. Then, a ton of ways relating amounts and timing have developed around this quick remedy, which tend to make it sound even more realistic.
There is no explanation for why this approach does not work, simply because a scientific approach requires you to demonstrate the opposite, i.e., that a particular technique or procedure works. It makes a small but significant difference: if adding potatoes to a dish that is overly salty does not change the flavour, the repair does not work, period, no need to state the obvious.
Why not give it a try for yourself and see what happens when you add a potato to a salty soup? The soup will remain salty, but you will now have a lovely boiled potato instead. Some people have even tried to tackle the issue scientifically by conducting an appropriate experiment, which you may repeat yourself provided you have the required tools.
Experiment
Take two 400 ml water samples and add the same amount of salt to each, say 35 grams. Once the salt has dissolved, boil the two samples for the same amount of time without stirring. At this time, add an 80-gram potato that has been peeled to one of the samples. After 30 minutes, finally take both samples out of the heat and filter them. Afterward, conduct a refractometer analysis. The results from both samples are identical, demonstrating that the potato did not diminish the salt content. Given that potatoes are unable to absorb any substance selectively, rather than asking why the technique does not work, ask yourself what chance it has of working.
Fix
Actually, there are a number of techniques that are effective. If the overseasoned ingredient hasn't already been included into the recipe, the simplest approach might be to simply wash the salt off of it. Add some kind of liquid, such water or milk, to dilute it. To prevent your meal from being too thin, you might need to increase the proportions of the other solid ingredients as well, but hey, the worst that can happen is that you'll have extra soup. It might be best to simply double the recipe while you're at it, invite every neighbour, and turn the tragedy into a celebration. Alternately, you might include a sweet component to help offset the flavour. Set the acid to work. Lemon juice, which can hide the salty flavour, enhances overly salted cuisine to its full potential. Alternatively, depending on the meal, you might use vinegar or another sour citrus.
But preventing a salt emergency altogether is the greatest approach to maintain the flavour of your food. Don't measure salt or other potent spices over your pot or skillet because a mistake there could undo all your hard work. Keep an eye out for components that already include salt, such as some broths or cheeses, as they may cause the salinity level to sneak up on you. Potatoes, on the other hand, are usually a great side dish.