The best way to tell if you get too much sodium in via sodium ascorbate is to look at the factors likely to make you retain water in your current health state, your total sodium daily intake, etc.
Current CDC statistics have the total daily sodium intake of the average american at an estimated 3 grams for ages 2 and up- drastic, but the warnings against sodium have a lot to do with the sometimes antagonistic relationship between sodium and potassium salts in the body. Both are necessary for normal healthy heart function, and it's important to aim your diet for a maxiumum potassium intake. (Fx, boiled potatoes, vegetables with the steaming/boiling water saved for sauce, bananas).
The salt content of sodium ascorbate is 180 mg per 1 gram total sodium ascorbate powder. It tastes a bit revolting in a thick dilution, and quite fine in a thinner- you'd have to track your actual intake yourself. I find the thicker dilution to be a passable excuse for a mouthwash ;) that can actually be swallowed. Hydrogen peroxide is still the absolute best for that though.
The thing about vitamin C megadosing is that you need to be aware that your kidneys will have some extra work to do to excrete it. I believe most of the anti-vitamin-C literature I am finding is based on ascorbic-acid-based research, completely independant of co-factor minerals and bioflavanoids. As a chelator vitamin C ups the amount of water and minerals passing through your urine.
Get these minerals down pat and in the right porportions for yourself so that you are in good standing before you C-up-
The one factor you need to be wariest of when taking C is copper depletion. Copper depletion contributes to heart palpitations and symptoms of hyperthyroidisim- it has a close relationship with zinc in maintaining metabolisim.
I have not experienced adverse effects since purchasing my big tub of Sodium Ascorbate, and I have used it by putting two grams in a tiny bottle, diluting with as much water will fit in the bottle, and then sipping or putting a few drops in water or lukewarm tea.
I'm hoping a friend of mine will agree to mix some rosehip-powder he bought recently with my sodium ascorbate. I think there are some interesting points behind the whole bioflavanoid thing, but I haven't found rock-solid data on it yet.
(BTW, look up vitamin D3 if you're looking for a metabolisim boost. Vit C and Zink are strongest on the Immune system side of things. ;)