'Salt' symbolizes the desire of truth and good to be conjoined with each other. So, a salt can conjoin water, which corresponds to truth, with oil, which corresponds to good.

Salt can also have a negative meaning. 'Lot's wife becoming a statue of salt' signifies all the good of truth being vastated, or laid waste, in the church that Lot represented. In that story, Lot's wife represented a form of 'truth' that turned itself away from 'good,' and looked instead to doctrinal matters. Because 'salt' can signify vastation, and 'cities' signify doctrinal aspects of truth, in old times they sowed cities with salt when they were destroyed to prevent them from being rebuilt, as in Judges 9:45

(References: Arcana Coelestia 10300)

2120. Every single detail of what the Lord has said in Matthew 24:7, 29; Luke 21:25, about the last times - about the sea and the waves roaring then, about the sun being darkened, the moon not giving its light, the stars falling from heaven, nation rising up against nation and kingdom against kingdom, and so on - means the future state of the Church, when its Last Judgement takes place. By 'the roaring of the sea and of the waves' is meant that nothing other than heresies and controversies within the Church in general and in the individual in particular will reverberate in this fashion. 'The sun' is used to mean nothing other than love to the Lord and charity towards the neighbour; 'the moon' to mean faith; and 'the stars' cognitions of faith which in the last times will be so darkened; their 'not giving their light' and 'falling from heaven', that they will disappear. The Lord has also spoken in a similar way in Isaiah 13:10. Also, by 'nation rising up against nation and kingdom against kingdom' is meant nothing other than evils clashing with evils, and falsities with falsities. And so on. There were many hidden reasons why the Lord spoke in this fashion. That seas, sun, moon, stars, nations, and kingdoms have such meanings I know for certain, and have shown in Volume One.