Warning: This contains a discussion of Christian Exegesis, or biblical interpretation. There is some science stuff as well and a comparison of the two. But if that kind of religious debate is not your cup of tea, you might want to skip this post. We'll wait for you to move on.........
Ye are the salt of the earth: but if the salt have lost his savour, wherewith shall it be salted? it is thenceforth good for nothing, but to be cast out, and to be trodden under foot of men. Matthew 5:13 King James version
From a purely chemical reasoning, I really don't see how it could "lose flavor". . The flavor comes from the ionic bond breaking when it goes into solution, as in when it dissolves in the saliva in your mouth. IF there is physical salt, then those bonds are present. If the bonds are present, then they will break in solution. If they break in solution, there will be flavor. Therefore, they must be talking about something else. I think what has happened here is that a copy error occurred in later editions, and someone changed "savour" to "flavor".
I have also read this (in Mark) as "has lost its saltiness". Comparing the two, that would indicate the meaning as "that which makes it salt". If salt isn't salt, then it is simply dust, and should be put where the rest of the dust is...... In the street to be trod upon, because that is what makes dust.
But I will tell you that the intensity of flavor does change with the salt composition. PCl, commonly known as "lite Salt", used primarily by people on a low sodium diet, is less "salty" tasting than NaCl. On the other hand, most places are going to have only one kind of salt. The P- Cl+ doesn't form when the stronger bonding Na- is present. The Na is stingy, and takes the Cl+ all for itself. Why? Don't know, not a chemist. But those two salts are not found together in nature.
The other concept that you might consider is that the Bible was discussing the preservative nature of salt. If salt has lost its ability to save (savour), then what will preserve the salt? Salt was THE preservative method, and salt mined from the earth (like in Salzburg, Austria, or in Wiesliczka,Poland, or in Krewka, Pakistan) has been in existence since the beginning of the world. So if you want to save something, wrap it in salt. If your salt doesn't save your stuff, then throw it away as worthless.
Now, as to my interest in the passage..... Salt comes in a rocks, or in gravel if you have a lot of it. larger towns pave their streets to stave off the mud. Spreading gravel is the equivalent of paving. If you have a large salt mine to hand (like you know, the Dead Sea, maybe), it is easier to mine the salt than it is the limestone, and break it into gravel. This is very dirty salt, pretty much the equivalent of our road salt, and definitely not fit for eating, or preserving food FOR eating. For that purpose it has to be washed and refined several times. That refining is what makes salt so expensive. This raw stuff is literally dirt cheap. Road engineers will use whatever gravel is closest and easiest to access. Sand stone, limestone, granite, broken reef, coal cinders, what ever they can get cheaply.
Why would Jesus have used this visual if the common culture was not familiar with the image?
From an engineering perspective, this has some really interesting characteristics. Rain does not percolate down through the soil like it does here. It evaporates back UP out of the soil in that region. So the cycle would be.... Salt the road, rain falls and dissolves the salt, enters the earth to a depth of no more than 18", then evaporates leaving the salt behind. The Salt then hardens the soil, creating a hard surface that is more impervious to rainfall than the surrounding ground. IOW, it creates a hard pack road NATURALLY!!!!! in *my* book, that's pure f*****g GENIUS!
Cultural support for this theory comes from a practice distinct to the region. EVERYbody goes barefoot everywhere around the world. Indians, American Indians, Polynesians, Greeks, Romans, Egyptians, Mayan. Everybody. But the ONLY place that has a ritual foot washing with oil is the Holy Land.
Normal dust does not dry out the feet severely. Salt dust will cripple the feet in less than a week because it will dry the skin and make serious bleeding cracks. The only way to correct that is to wash the salt dust off, and rub oil into the skin. And this practice is documented not once, but several times in the gospels. Mary does it to Jesus. Jesus does it to the disciples, widows to saints.
At least, that is MY take on it.