Expert: Mike Fulcher - 7/22/2007

Question
what is the calculation which will tell me  how many grams of salt to put in a 1000 mililitres of water. For instance I need a concentration of 100 ppm of salt in 1000 mils of water based on weight. Thanks

Answer
Since you're doing this by weight, you would take the weight of the water (1000 g), then divide by 1000000, which would give you 1 mg.  This is equivalent to 1 ppm by weight, so 100 ppm would be 100 mg.  You'll need to subtract this from the water weight for it to be accurate, so use 999.9 g of water if you're really trying to be accurate.