The Planted Tank Forum - View Single Post - KH Standard / How to
View Single Post
Old 08-27-2010, 10:18 PM   #15
Darkblade48
Moderator
 
Darkblade48's Avatar
 
PTrader: (3/100%)
Join Date: Jan 2008
Location: Japan
Posts: 9,329
Default

As KevinC mentioned, you can easily increase your precision by increasing the volume of water to be tested.

The gH and kH test kits work on the basis of titration. As KevinC also mentioned, if your 4 dkH reference solution is slightly off (i.e. 4.1 dkH), then it will require that 5th drop to change the colour to a bright yellow.

As for where your error is coming from, I would suspect the sodium bicarbonate as well. Despite it being a brand new box, it is not completely air tight, and there are surely impurities left over from the manufacturing process, etc. However, since it is going to go into a drop checker, which is not the most precise tool anyway, you can probably get away with the reference solution you already have made up.
__________________
Anthony

A Primer to Pressurized CO2 and A Primer to Planted Tanks
Eheim Pimp #362 - Eheim 2213 x2, Eheim 2028, Eheim 2217, Eheim surface skimmer and Eheim autofeeder.
Victor Pimp #33 - HPT272-125-350-4M
Darkblade48 is offline   Reply With Quote