Replied by Ted (Bangkok, Thailand)
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.