[sundrops]

the melting point of salicylic acid is 159 degrees celcius.

now while conducting an experiment would the melting point be any different? for example would the melting point be higher/lower due to impurities? or will melting point always be the same? or if it ends up as a pure substance would the melting point be the same as the theoretical melting point?

can anyone help me out here? I'm a little confused.   lol as you can tell.

[mike]

Hiya, I don't know from your post what experiment you are conducting with salicylic acid but the literature melting point (mp) is usually for the pure substance.

Small percentages of impurities in a sample generally decrease the melting point of the sample.

At the end of the experiment, you could test the melting point of your sample, if the melting point is below the literature then it probably contains impurities.

You may also want to compare the melting point of your sample after the experiment with a sample of the original solid, or with a a sample you know to be pure.

Mixed melting points are another useful experiment in which the sample from your experiment can be mixed with a pure sample and see if this changes the melting point.

Good luck!

[sundrops]

in the experiment we are conducting, i will be synthesizing salicylic acid from methyl salicylate - so the probability that my sample will be pure is fairly slim. is it safe to say then that my melting point will be lower? we are using boiling chips and the like that may account for the product to be unpure.

[mike]

I would say that your melting point would be lower than the literature value.

Boiling chips should not affet the purity/melting point of your product as they should all be removed in the work-up of the reaction. (don't try to get mp of boiling chips as they don't melt )

Impurities may include, solvent, starting materials or byproducts of the reaction.

Generally if your melting point is close to the literature and has a narrow range (when it starts and finishes melting) then it is relatively pure.

If your melting point is significantly lower than the literature and quite broad then it is probaly impure.

[sundrops]

lol - thanks!