Check out this thread -
http://archive.reefcentral.com/forum...readid=1283622
and how do I get exactly 161 ML?
I used a graduated cylinder the first time. Second time I used a 10mL syringe. Both solutions yielded the same results. The thread above also says you can use a 2L Coke bottle filled to the top with RO/DI and 1/4 cup + 1 tsp of Morton's. Supposedly the Coke bottles are the same and this formula yields the same 35 ppt solution.