Confusing acid dilution calculations

[goldsilverpro]

Unfortunately, when you buy acid, it's usually sold as a weight (or, mass) percentage(weight of acid/weight of acid plus water). I never liked it either but that's just the way it is and you have to learn to deal with it. Working in moles would be much, much easier.

Using percentages. How many here can calculate how much water would be added to convert 500ml of 60%(w/w) nitric to 30%(w/w) nitric? It's not 500ml. It's 664ml. Must first use S.G. charts, graphs, or a formula like the one I gave above. Not intuitive.

On the other hand, how much water is needed to convert 500ml of 16 Molar nitric to 8 Molar nitric. It's 500ml. Lots easier. Very intuitive.

 

[j2000]

What percent "standard" of nitric acid when we wanna make good AR ?

I have 65% NA, and i want to dilute to be 10% NA for 1000mL.
I use calcutor and calcultor said: 116.52mL nitric acid + H20 883.38mL.


This is correct?

Regards

Joel

 

[solar_plasma]

What percent "standard" of nitric acid when we wanna make good AR ?

"Good AR" is when you use enough HCl to cover the material to be dissolved and add only as much nitric as needed, though use at least 3-4 parts HCl per 1 part nitric. If you use SMB for the precipitation, it will consume some HCl and you need even more HCl. The concentration of the nitric you are adding is not important.

I have 65% NA, and i want to dilute to be 10% NA for 1000mL.
I use calcutor and calcultor said: 116.52mL nitric acid + H20 883.38mL.

Better and easier to think and calculate in molarity and weight than in % and ml. Why do you want to dillute your nitric. I can't see the necessity. Just add about 1,7ml of your 60-70% nitric per each gramm of gold. Add it in small increments, give it good time to react, even more since your material is in shape of fine powder and stop adding, when the reaction stops (it has stopped when there is no detectable production of NOx gasses anymore).

I have no clue about ores and concentrates, so wait if other opinions or corrections will pop up.

 

[goldsilverpro]

What percent "standard" of nitric acid when we wanna make good AR ?

I have 65% NA, and i want to dilute to be 10% NA for 1000mL.
I use calcutor and calcultor said: 116.52mL nitric acid + H20 883.38mL.


This is correct?

Regards

Joel

I get exactly the same results that you did - 116ml of 65% diluted to 1 liter = 10%

 

[rickbb]

As Solar posted, (and I have learned the hard way), if you mix your AR based a ratio or % type of formula you will be wasting nitric.

Use only the amount needed to dissolve the gold. You will find you need somewhat less than the general rule of 1 to 3 or 1 to 4 ratios.