Finding the Best fitting curve for a graph?

[Ascleipus]

Hi, I m unsure whether or not this should perhaps be in the homework forum, however one might say this is more of a technical issue. I recently conducted an experiment for a report I intend to write up promptly, and I wanted to find the best fitting curve for these values. I tested how different salinities affect the degree of absorption of Polyacrylic acid. This is what I found
Trial 1 Trial 2
Salinity 0M 558g 533g
0.25M 95g 93g
0.5M 79g 79g
0.75M 63g 67g
1M 54g 60g

original mass of the polymer was 3g.

Essentially what I would love to find out is how I might be able to get a best fit curve for this graph.

Help would be much appreciated

 

[Borek]

I don't see how to do it without knowing a priori what kind of function described the dependence. Apparently at low salinities the result is extremely dependent on the concentration, so you would need much more data points to cover this area to be able to suggest something that would be not just a wild guess.