I thought I had explained that methionine, not salt, is the "medicine" that makes c/d and s/d effective against the formation of struvite crystals.
Actually, you first stated it was salt, plain old salt to be exact (see your previous reply) . Then you come back with another reply that it was methionine, not salt. ( see second quote). I'm sorry, but to me, you seem to be changing your information on the same subject, which is very confusing. My only point was, whatever the ingredient is in Hills CD food, it creates thirst which makes cats drink more water. This keeps crystals from forming, so that is all I care about. Period.
Actually the "medicine" you are referring to that creates thirst in the cat is salt, plain old salt. The reason c/d and s/d are prescription is the added methionine which is an amino acid which acts as a urine acidifier. The urine acidifier bring urine pH down to levels where crystals do not form as easily. Feeding a diet high in meat also acts as a natural urine acidifier.