I use sodium lactate in most, although not all of my soap formulas. In my CP, I find it lends a creamy depth to the lather....almost as if I had added goat milk or coconut milk as my soaping liquid instead of water. It also lends a bit of extra hardness, which helps soap to unmold easier, especially soap poured into intricate, decorative molds. It helps those to unmold smoothly and easily without incurring damage to the surface.
In my HP, it helps the soap batter to smooth out more, making it more jam-like instead of more dense, mashed potato-like. I can also feel the same creamy depth to the lather that it gives to my CP.
In my liquid soap, it helps to dissolve the soap paste into liquid soap much quicker than normal when I go to dilute.
And I also use it in my lotion, where it acts as a humectant, drawing moisture to the skin.
I use it @ 3% ppo in my soaps and @ 3% in my lotion.
IrishLass