How much sodium silicate to get 2ppm in 200mL?

[Miami Reef]

I redid the experiment. I couldn’t wait to get the new vials. I needed to know NOW!

Phosphate before silica: 4ppb

Put silica in syringe and used my 0.22um filter. Added a drop directly into the 2L test beaker.

Silica flashed 2.00ppm. I wonder why? I think the drop was larger because of the strainer. I estimated the Si to be about 3ppm based on the color. It was a nice dark blue color.

Tested PO4 after: 19ppb

0.046ppm increase.


This experiment would have been better if I knew the exact Si concentration. I can redo it again when I get the new vials.

 

[Randy Holmes-Farley Verified Community Expert]

I don’t recall seeing any discoloration or solids in the water glass I used in the past, but I also may not have looked carefully.

 

[Miami Reef]

I don’t recall seeing any discoloration or solids in the water glass I used in the past, but I also may not have looked carefully.

Did you see Taricha’s post? He received my silica bottle and tested it himself for phosphates.

Thanks to @Miami Reef for the bottle of water glass. Here's what I found with the Loudwolf water glass silica dosing....
(tldr: nothing much different than what @Rick Mathew and I have measured previously.)

first, the bottle is a mess inside. lots of white solids and some dark particles.

I ran it through a 1um filter because what's specified in the MSDS is supposed to be a liquid and the solids are certainly not what we want.
"Substance name : Sodium Silicate Solution
Concentration : 41%
Formula : Na2SiO3 + H2O
CAS No. : 6834-92-0, 7732-18-5
Product code : LW-WATERGLASS
Synonyms : Waterglass"

I added measured amounts of the liquid to 1L of tank water to make 0, 1, 3, and 4ppm SiO2 solutions. I was over 30% too high, then I realized I goofed and made stock by volume without looking at the density. Correcting with the MSDS info...
"Relative density : 1.39 g/cm3 at 25 °C (77 °F)"
The hanna SiO2 measured comes out right at what was expected. So the liquid portion is exactly what it should be in SiO2.

Here's what the hanna ULR P checker gives for the various concentrations between 0 and 5ppm SiO2.

Stock SiO2 expected (ppm SiO2)	hi736 ULR P reading (ppb P)
0	30
0	23
1.40	27
1.40	22
4.17	27
5.56	30
5.56	43
5.56	32

This fits decently well in context with what Rick and I have measured before....Yellow stars are the new measurements.

(Green points are Miamireef data from post 23 using the hi736, so a little different but not hugely.)

So a couple of points:
1) the SiO2 in the loudwolf product doesn't interfere with the hanna ULR P checker any more than the small amount documented previously with other Silica sources.
2) I'd advise if you get the loudwolf product to filter the tons of solid material off and discard, if you have syringe filters that'd be ideal, but probably running it through a couple of coffee filters a time or two will work.
3) use dedicated hanna cuvettes for each test kit. Hanna sells extras. Using a cuvette to go back and forth between different tests causes weird results sometimes, even with lots of washes between.

 

[taricha]

@Miami Reef here's my calcs based on your last data.
assuming 1 drop = appx 0.05mL, you added 6.7ppm SiO2...

so plotting your 0.046 ppm PO4 apparent increase (green star data point)....

It lines up perfectly with the measurements that Rick and I have made for SiO2 addition.

 

[Randy Holmes-Farley Verified Community Expert]

Did you see Taricha’s post? He received my silica bottle and tested it himself for phosphates.

Yes.

 

[Miami Reef]

@Miami Reef here's my calcs based on your last data.
assuming 1 drop = appx 0.05mL, you added 6.7ppm SiO2...

so plotting your 0.046 ppm PO4 apparent increase (green star data point)....

It lines up perfectly with the measurements that Rick and I have made for SiO2 addition.

Yes! I remembered I weighed a drop one time and it was like 0.03g. I even calculated it to be around 7ppm.

I wrote this

Yesterday I added about 7ppm of Si and the phosphate vial turned dark blue.

This was from a full drop. So yes, I’m so happy to read I was in line with you and Rick Mathews.

 

[WhatCouldGoWrong71]

How should I be mixing this stuff? I had Dino’s, and went through a bottle of brightwell stuff like I was 17 and hanging out on the corner with a brown bag. It was recommended to me to use this. I have 130 G system and just want to keep doing daily dosing to keep the LCA away. This stuff is like a syrup and when put a tad bit in water it looks like it separates. I only have a Salifert SI test kit which I see doesn’t really work. I also don’t have anything that doesn’t measure super accurate in terms of ML, I have lots of syringes but all are in increments of 1. Thoughts?

 

[Miami Reef]

How should I be mixing this stuff? I had Dino’s, and went through a bottle of brightwell stuff like I was 17 and hanging out on the corner with a brown bag. It was recommended to me to use this. I have 130 G system and just want to keep doing daily dosing to keep the LCA away. This stuff is like a syrup and when put a tad bit in water it looks like it separates. I only have a Salifert SI test kit which I see doesn’t really work. I also don’t have anything that doesn’t measure super accurate in terms of ML, I have lots of syringes but all are in increments of 1. Thoughts?

You’d need about 2.1g to get 1ppm in your tank. Dose once per week.

Exact dosage is not critical. Just eyeball about 2.5mL and dose it once a week.

The separation when added is likely magnesium hydroxide. It will redissolve. Dose in a high flow area of the sump.

 

[Randy Holmes-Farley Verified Community Expert]

It’s also fine to dilute it with ro/di if that helps it disperse better/faster. It will locally cloud the water a bit with temporarily precipitated magnesium hydroxide due to the high pH.

 

[taricha]

Right. I dilute and pour into a powerhead. Cloudiness gone instantly.

 

[Miami Reef]

YESSSSSSS!!

@taricha @Randy Holmes-Farley @Idech
@Garf


I did it!!!

I got the new Hanna vials and caps. I am specifically going to use each one for their own test kits. No cross contamination.

I prepared a 35ppt salinity solution.

Tested PO4 before: 12ppb. I used ULR ppb with the ULR ppb reagent

Then, I filtered the silica with my 0.22 syringe filter (it was VERY difficult to push out the silica through the filter)

I added a fraction of a drop.

Here’s the Silica test with the new vial and small drop:

Then, I tested the phosphates again:

Jonathan, Can you please input my new values to the graph? I want to see the new chart.


I believe the silica just needed to be filtered. There will only be an interference if you dose too high or if the product is messy inside.

 

[taricha]

Here's what that looks like @Miami Reef . (green stars.) You can see it fits in the area where there is no detectable increase in PO4 measured.

We should probably refer to the interference of SiO2 on phosphate measurements as an interference from SiO2 overdose.
Because there's no good reason to dose amounts of SiO2 high enough to actually cause this effect to appear.

 

[Miami Reef]

Here's what that looks like @Miami Reef . (green stars.) You can see it fits in the area where there is no detectable increase in PO4 measured.

We should probably refer to the interference of SiO2 on phosphate measurements as an interference from SiO2 overdose.
Because there's no good reason to dose amounts of SiO2 high enough to actually cause this effect to appear.

Beautiful. I love how I’m in the graph with you guys.

Now here’s the kicker: Do you think those solid masses in the silica product contain particulate phosphate (real PO4 reading), or is it just messing with the test (false high)?

Because when I did not filter, I got a PO4 increase, even when targeting 1.5ppm.

 

[taricha]

hard to guess what the solid contaminants are - the white stuff I'd guess is mostly some solid form of Silica, since there's so much of it in the bottle.
It could be responsible for causing Si levels to overshoot a dosing target and go too high.
The black solids - who knows.

It is hard to guess what the effect of unknown solids would be on chemical tests. I'm glad that the filtered liquid behaves exactly as expected so the solids can be discarded and we don't have to think about them.