[Intanjir]

Ok, I did that titration of HCl into the sodium silicate with universal indicator and it changed color to orange within 5% of when you would expect it to given the concentration given on my stuff's label.

[Tittywahah]

Ok I did the titration and here are the results so far:
Adding phenolpthalein to the 5g Sodium silicate dissolved in water, it turned pink and was at a PH above 11
Using 0.5M HCl as the titrant and 5g sodium silicate dissolved, HCl added until pink disappeared and the PH strips measured below 6.8 (Strips range 0.3 increments;
Results after calculations: 0.93g Na₂O this is 18.6% in this batch of powder

My other Sodium Silcate solution has 12% Na₂O and 30% silicon dioxide at 1.5g per mL.

I will have to do the titration again tomorrow to be sure. I think I need to stop before the 6.8 is reached but also take a measurement both when the pink colour disappears and then when the PH is at 6.5.  we will see what the results are then.

[Tittywahah]

I knew I made a mistake yesterday, tiredness.  Did a comprehensive test this morning.

0.5M HCl (Density 1.18) added to 5g Sodium Silicate dissolved.

at 35mLs the phenolpthalein turned from pink to clear
at 39mLs  PH at 8.3 exactly
at 40mLs PH at 6.8 + precipitate began to form
at 42mLs PH at 1.0

Taking the value of PH 6.8 the Na₂O content is at 0.62g per 5g which is 12.4%

Now attempting the Silicon Dioxide amount

[Intanjir]

12.4% Na2O seems low for a powder, might make some sense of why it was so stubborn to dissolve.
Hopefully you get at least 25% or so weight loss on roasting.
If you don't get any weight loss on roasting the powder then something is wrong, hehe.

[Tittywahah]

Yes, absolutely. It is actually crystaline and contains very very hard lumps which I have to break up.  Is it harmless to roast in the cooking oven?