Citric acid -- How much to use???

Hello,

This weekend I plan on changing the coolant and flushing the system out on my 87 190E 2.6 (M103). I have obtained MB degreaser and MB citric acid powder as per the plethora of posts on another list. The degreaser dilution is very clear from both the posts and the bottle itself -- 50g/L, or 450g for a 9L cooling system like mine. The recommendations for the citric acid dilution vary wildly however. There are, naturally, no instructions on the 500g bottle. Here are the 3 different amounts I have found:

Quoted from the Mercedes Microfiche, Engines 615, 616, 617.91 Mechanical III (not my engine, but how different could citric acid dilution be between engines...):

"Fill the cooling system with a 10% (100g / liter) solution of citric acid and water."

That works out to nearly 2 500g bottles of citric acid for my 9L system.

From a post on another list:

"The part # is 000 989 10 25 - that's enough to do one cooling system any size..."

About half the concentration of the previous post.

From a mechanic at Fletcher Jones MB in Newport Beach:

"Use about 3 tablespoons per gallon."

Huh?! There's probably more acid in straight tap water than that! I think he might have been mis-informed, so I am ruling that out for now (unless someone can verify that he was indeed correct).

So... Does anyone know how much should be used? I would greatly appreciate any input. Thanks!

John