For example, I would like to take two images for same glass which has some water the first image it just a water and the second one has some salts dissolved inside the water.
It is better to upload two different sample image of each salty and pure water.After it will be easy to select an appropriate feature and detect salty water from the pure one.
I think that the color and the texture of the salty water is different from the image of the pure water, to make sure, follow what Hossein Soleimani has said.