I took the average of 20 x 1/4 teaspoons(the smaller, the less accurate any weights will be). They where off by about 0.08 grams at most as long as they where level and the user was somewhat careful.
1.67 grams was the weight I arrived at for a 1/4 tsp using the KNO3 I had.
So with a replication no# of 20, I'm pretty confident on the errors involved.
Now if someone is sloppy, then the error goes up, this is true for anything however.
So the method itself is not inaccurate, it's the poor measurement techniques etc that contribute, or the different brands of KNO3 etc.
You can buy a simple gram scale for about 20$ that goes to 0.01 gram accuracy.
None of this is really a big issue unless you dose smaller than 20 Gallon tanks, in which case, making a liquid, then using say, all of it up 4 weeks(the time), can be done and pretty accurate.
Say you want to make a 4 week batch of dosing solution.
Say the tank is a 5 gallon tank.
You'd add 3/4 teaspoon of KNO3, about 1/3 tsp of KH2PO4 to 280mls of water.
Then dose 280 mls by 4 weeks, or 280mls/28 days= 10mls per day
You can change the time and volume to anything you want, just provided you can dissolve the ferts into the water.
Just divide the standard dosing routine in EI, add to water, then divide the mls of water/days you want to dose.
Note, this is for daily dosing(10mls per day example), you could dose 30mls 2-3x a week also.
Regards,
Tom Barr