# Can I calculate the maximum concentration of sucrose that will dissolve in water at STP using physical constants?

I am interested in identifying the maximum solubility of sucrose in water. Can this value be estimated based on the physical properties of sucrose?

Eventually I will need this in degrees Brix (%w/w).

this question represents is a specific case of my question at biology.SE

-

## 1 Answer

The solubility of sucrose in water at 25 °C is given as 2000 g/L. But, that doesn't tell us if this solubility, given in units of g/L, is expressed as a molar concentration (aka molarity) or as a molality. That's because molarity and molality are equal for diluted solutes (which don't contribute much to the total mass of the solution), this does not hold for concentrations as high as 2000 g/L.

Thus, you have to turn to other sources, which are careful of specifying the quantity given:

Now that we're clear about what is specified, you can turn these quantities into any other you want. For example, if I understand the definition of degrees Brix correctly, we can get the following approximation: 1 liter of water has a mass of 1 kg, plus 2.1 kg of sucrose in it gives the solution a mass of 3.1 kg. So, given that you have 2.1 kg of sucrose in a 3.1 kg solution, you'd be at 68 °Bx.

-
I was looking for the value "solubility of sucrose". Thank you. But, is this something that is determined empirically, or can it be derived from the chemical properties of sucrose and H2O? Can the density of the final solution be similarly derived? – Abe Mar 8 '12 at 14:50
@Abe this is determined either from experiments or atomistic calculations (which are just in silico experiments). Same goes for the density of the solution. Generally speaking, properties of solutions cannot be determined by simple calculations except in the limit of low concentration… – F'x Mar 8 '12 at 15:12
also, if the solubility is 2000g/L, does that imply that the final solute volume would be 1L, or that the total volume of water is 1L? – Abe Mar 8 '12 at 15:37
@Abe that's in fact the crux of the matter. I'll rework my answer completely to answer that clearly… – F'x Mar 8 '12 at 19:35