Quote:
A formula:
Basically, a gallon of water at room temperature weighs 8.343 lbs, or about 133.5 ounces. But wait! Isn't a gallon 128 ounces? It is 128 fluid ounces by volume, but a fluid ounce is the volume of one ounce of boiling hot water, at which temperature water is less dense than at room temperature. As a result of the density difference, a fluid ounce volume of room temperature water will weigh 1.043 ounces on a scale; and those are the ounces that matter.
Divide 133.5 ounces by 19 to get the amount of anhydrous citric acid you will need to dissolve in a gallon of water to make the combined solution 5% citric acid by weight. That works out to 7.028 ounces. 7 ounces is more than close enough.
So, what is the volume of 7 ounces of anhydrous citric acid? Per what I said earlier, this will vary. All I can do is report the weight of anhydrous citric acid powder I have, as I scoop it and level it from the 10 lb box I bought. A half cup (4 fluid ounces) of the powder weighed 3.83 ounces. The bag is mostly powder with lumps that are not very hard to break up, so it has a bit of moisture in it. I am not set up to do a titration to determine exactly how much moisture, so that just has to be part of the normal error. It would take 7.31 fluid ounces of my powder to get 7.00 ounces by weight. Given the non-critical nature of the mix, if I didn't use a scale and was forced to use volumetric measures, I would just measure 7 fluid ounces of the powder out (1 cup minus two level tablespoons), and add that to a gallon of water.
Edit/Add- The 4 tablespoon & soaking for 4hrs with 2 minutes shake time at start & finish resulted in clean brass, inside and out.