# Clarification of Solution Amounts

Posted by R on 12/28/2007

Hello Ted, I assume it was a total error in what you wrote online re: the making of 10% solution of SFS in water when you wrote.... stores sell 100% sodium thiosulfate powder, but I don't know how much to get and a recipe to make 10% solution. It is on a per weight basis. 30 grams of sodium thiosulfate in 100 cc solution of water. 1 cc of water equals 1 gram of water. Am I correct? isn't it 10 grams SFS to 100cc water or 30 grams SFS to 300cc water?? correct?? not that I would know... anyway, I bought the 100% SFS crystals from a pool house company and it's here now, but I do not know how to mix this together... unless it was NOT an accident that you put 30g sfs to 100cc water... let me know thanx soo much!

Replied by Ted
Bangkok, Thailand
383 posts

Dear Robert, A simple way to remember is 1 gram of water = 1 cc = 1 ml = 1 gram of water. This means in 90 ml of water, plus 10 grams of sodium thiosulfate (STS) would get about 10% sodium thiosulfate, roughly. It doesn't have to be exact. If I am working with 30 grams, then it's 270 grams of water to get a 10 STS solution. Here is how it is calculated: Weight of STS/(weight of STS + weight of water) x 100 = concentration of STS% The concentration of STS is based on TOTAL weight. Again all these are approximate figures in my use, and this is the proper way to calculate. You need to divide by TOTAL WEIGHT which equals to weight of STS plus weight of water.