Iron sulphate on lawn

Hi all, 

Just wondered if you may be able to give me some advice on applying Iron sulphate to my lawn to give it a bit of a green up. My lawn is 85m2  so i was thinking of just using 85g of the iron sulphate. Im just not to sure how much water i would need to mix with the 85g to apply it. I have a 10l watering can that i plan on using. Do i simply just fill up the can with water do a test run with just water and see how far round the lawn i get then work out how many full cans of water it will take to finish and just devide the mixture evenly between them?

Hope you may be able to assist 

Many Thanks