I came across this in a thread on Na & K carbonates "Basically, just remember, L S, B C L, S P A All potassium,nitrate salts are soluble.. however, chlorides,carbonates and sulphates are an exception.For chlorides, all chlorides are soluble except lead chloride and silver chloride..all sulphates are soluble except barium sulphate,chloride sulphate and lead sulphate..for carbonates,sodium,potassium and ammonium carbonate is soluble while the rest are insoluble.. as as sodium and potassium are very reactive when reacted with water due to the reactive series of metals..u can seperate sodium and potassium with their solutions by titration, changing them into a oxide or hydroxide... " I presume the Chloride Sulphate is a typo for Calcium Sulphate? But the thread is not editable. But secondary question, how do you remember a mnemonic like that? When I read it, I could not at first connect it at all to what followed. Then when I realised it was supposed to be a mnemonic, I had to check it against experience to know whether it was true. It's easy enough to remember these low solubility compounds, because that's what you see when you use them, but how anyone remembers the letters I don't know. And is it helpful to call these insoluble when Severn Trent / South Staffs supply calcium, carbonate and sulphate ions all in the same solution to my tap?