Hello!
So i am a little confused about something. I've been trying to measure density as per CuCl2 document, using a lead-acid battery hydrometer.
Solution "in work" as in dissolving copper and with a bubbler, colour, dark. read 1.10. another solution, been re-generated and turned bright emerald green,
reads 1.125.
Why then the document talks of density of 1.25 or more? Am i measuring it wrong?
Thanks
Depends on how much copper is in there dissolved. Copper chloride has very high solubility in water, 620g/L. By classic AP dissolution, you can be theoretically close to this, if no acid escape during the process.
But more realistically, the real system getting close to saturation point, probably not happening.
If the hydrometer can be faulty, there is another approach to density measurement. Take good scales, capable of measuring at least with precision of 0,01 g (cheap ones from e-stores can be just fine). Take volumetric flask or graduated cylinder, fill it with precise volume of solution at issued temperature, weigh it, and then calculate the density from weight and volume measured. For ballpark +-5-7% measurement it is more than sufficient.
Density is connected to the ammount of dissolved CuCl2 in solution, and it will slowly rise with CuCl2 content. If there is unconsumed HCl, it will also skew the readings to some minor extent.
Validation of hydrometer readings - easiest approach:
Prepare saturated salt solution (using ordinary tablesalt) by adding good
excess of salt to water (sat. soln. is around 330g/L), stirr it for few minutes and let it sit still for day or two - to equilibrate it. Now you should have saturated salt solution at given temperature - which density is known. Measure it´s density using your hydrometer and compare the numbers.
