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Potassium Sulfate Density question

Ictus

Ictus

Hey Guys,

I ordered some Potassium Sulfate powder so I could raise the K and S in my solution without overdosing the P, like most premixed nutes will do.

The only info I could find online (wikipedia) said it has a density of 2.66 g/cm3.

Since 1 Tsp = 4.928, I calculated using hydro buddy that 1/8 tsp added to 1 gallon of water should increase the EC by 0.5.

I did that experiment, added 1 gallon of tapwater, measured EC (.293), then added 1/8 tsp of Potassium Sulfate, trying to pack the stuff and level the spoon as well as possible.

The result was a .674 EC solution, an increase of .381.

76.2% as effective as my calculations thought.

So could this mean the real density of this powder form is 2.02g/cm3, or is there something else going on? Reaction with somethin in tap water perhaps.. or some kind of non-soluble filler? Hydrobuddy getting the EC wrong? Or possibly even I have the wrong compound?

Would you guys recommend dosing according to the 2.66 g/cm3 stat found online or my measured 2.02g/cm3 in terms of EC potency?
 
im pretty sure that hydrobuddy converts mg/l into EC. im not 100% but i dont think it takes into account different chemicals electrical conductivity when in solutions. if this was not the case hydro buddy would need to know exactly what chemicals make up a fertilizer in order to predict ec, which i know isnt the case.

all things considered you are off by 23.8%, id say thats accpetable givin you are using measuring spoons. this stuff could also be hydroscopic, i not sure tho
 
You have several problems going on at the same time which may compound the issue. One is you are mixing measures between SI and Metric, and using kitchen measuring spoons to take your measurements. 2nd you are using wikipedia for the data on your potassium sulfate instead of the manufacturers data sheet. The particular manufacturer might have added powdering or anti-caking agents to the material depending on if it is for agricultural use or labratory use, which will change the characteristics for your material.

You need a set of mL measuring spoons. You may need to check with a lab supply depending on the size you need.

Amazon and ETA have a "inexpensive" set of metric measures available they look to be the same set, 1mL, 2mL, 5mL, 15mL, 25mL. The difference is pricing and the cost of shipping.

http://www.amazon.com/Metric-Measuring-Spoons-Set-5/dp/B0017UHUQ4

http://www.etacuisenaire.com/catalog/product?prodId=599


1cc = 1mL for measuring volume
 
Thanks guys. I will get some of the more accurate spoons.
Sadly the stuff I got didn't come with any info. I got it off eBay from a big seller so I messaged them with the same info, hopefully they let me know.

I will probably err on the side of too low until I can be sure.
 
DP,

Just to make sure I understand the unit mixup properly, are you saying that my kitchen teaspoons are metric, while density in g/cc is SI?

In practice how different is it? I thought SI included metric but SI was more specific. Which of my measurements suffer from this? And the ml spoons would be considered SI?
Thanks again.
 
Density as measured in g/cc is metric/SI (Systeme International, pronounced with a frenchie, french accent)

American Kitchen spoons in teaspoon and tablespoon measures are not metric.

They do make metric oz, tablespoon, teaspoon measures, but not usually for the American market.
Metric ounce measure is a hybrid for simplification.

1oz = 2 Tablespoons (Tbls)
1 Tablespoon (Tbs) = 3 teaspoons (tsp)

if you are using metric ounces (this is really for cooking and guestimation not for labratory usage)
1oz = 30mL
1 Tablespoon = 15mL
1 teaspoon = 5mL

for labratory and industrial use
1oz = 29.574mL
1 Tablespoon = 14.787mL
1 teaspoon = 4.929mL
1/8 teaspoon = o.6161mL.
 
Ok, I did calculate using 1tsp = 4.929 using my spreadsheet.


I heard back from the eBay seller, and they told me all they knew ATM was 50% potassium, 17% sulfur. That was very slightly different than hydrobuddy's default values so I plugged em in, and scaled up to 0.5 tsp, supposing it to be 6.6g. Hydrobuddy predicted EC 2, and I tested 1.772, Accurate to 88.6%. Not perfect but pretty close.

Funny because hydrobuddy underestimated the EC of GH Micro by 30% and calmag was off by 100% !! It guessed 0.9 and I tested 1.85.

So I guess it's asking a lot to get a perfect EC prediction for the commercial mixes.


I'm going to order the metric spoons also. Thanks for your help.

I just did the same test again but more concentrated.
 
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