Diy.2 part, powder not fully disolved

[john08007]

Started making my own 2 part using the recipe online. For alk I used baking soda that I baked in my oven. Calcium I used Prestone driveway melt, magnesium I used epsom salt and mag chloride from BRS.

My question, the calk, alk still had undisolved powder on the bottom of the container the next day. I'm thinking maybe the recipe is the exact amount, my measuring cup not exact and the solution was a saturated solution so I added more ro water. Seem like a logical explanation? I'm thinking I may just need to tweak my doser to adjust for the concentration of my batch.

 

[bertoni]

I am not sure what happened. How much undissolved powder was left? If it was a small quantity, it might have been contaminants.

 

[john08007]

There wasn't much, it just looked like a layer of white powder along the bottom of the jug. So in the future is it best to mix exactly as the recipe states, siphon off the top clear liquid and discard the bottom if there is a precipitate there?im thinking this will work fine, it will just be a little more diluted and need to be dosed slightly more

 

[dkeller_nc]

If this was baking soda from the grocery store, it wasn't contaminants. It's possible that you didn't bake it enough to completely convert the sodium bicarbonate to sodium carbonate. Sodium bicarbonate is a lot less soluble than sodium carbonate, and the recipe calculators on-line are near the limit of solubility. Complicating matters is that sodium bicarbonate has a negative heat of solution, so dissolving it in RODI will lower the temperature of the solution somewhat, and all of the sodium bicarbonate won't dissolve until the room heat raises the temperature of the solution.

I can't comment about Prestone Driveway Heat. That may, or may not, be pure calcium chloride dihydrate. My guess is that if it is, it's a very low grade of calcium chloride, so yes, it may have all sorts of other things in it.

 

[bertoni]

You can discard the bottom layer if it's thin. I agree that some of it might have been sodium bicarbonate that didn't get quite enough baking. You can heat the solution to dissolve more if that's the issue, but I doubt it's worth the effort.

 

[hkgar]

I use a large pot to make the solution and stir over a low burner on the stove. It makes dissolving a bit easier and I always get it all dissolved, but takes a lot of stirring.