1.) When determining the melting point it's described in my text as recording 2 points in the melting process.
a) when the first drop of liquid is seen
b) when all of the compound is liquified
and since I have to determine the melting point of sulfanilamide pure and impure (I get the pure after crystalization and the impure is the before sample)
My question pertains to should I trust the temperature that is stated on the web. Secondly when seeing the "first" drop of liquid from the compound does it litterally present itself as a drop of liquid (descriptions in books can be misleading sometimes)
2.)What will happen if you choose a solvent whose boiling point is higher than the melting point of the compound to be crystalized?
-I was confused as to what was said before ...so..I'll propose my thoughts before I have to hand this in tommorow...
I think that if the boiling point is higher than the melting point wouldn't the solution boil before the compound to be crystalizes melts at all? (I thought about this awhile and it should be but isn't in my text)
1. It will be obvious when the first crystal melts. It may not be a "drop" as such so it isn't literal but you can't miss it. As for the literature mp, no, I wouldn't trust them for your samples. They will be good boundaries to guide you but the mp of your samples will depend upon the purity, both before and after recrystallization.
#2 I will leave. I know you and Bob Pursley have talked about it.
Thanks Dr.Bob for all your help, I'll make note of that when I do lab tomorrow =D
1.) When determining the melting point of a compound, it is indeed common to record two points in the melting process. The points mentioned in your question are commonly used:
a) The first point is when the first drop of liquid is seen. This indicates the beginning of the melting process.
b) The second point is when all of the compound is completely liquified. This indicates the temperature at which the compound has fully melted.
To determine the melting point of sulfanilamide for both the pure and impure samples, you should follow these steps:
- Obtain a small amount of the pure sample after crystallization, and another small amount of the impure sample.
- Prepare your melting point apparatus, such as a melting point capillary tube and a heating source, following the recommended procedures.
- Place a small amount of either the pure or impure sample into the capillary tube.
- Insert the capillary tube into the melting point apparatus and slowly heat it.
- Observe the sample closely for any changes.
- The first drop of liquid observed indicates the beginning of the melting process, and you should note the temperature at this point.
- Continue heating until all of the compound is fully melted, and note the temperature at which this occurs.
Regarding the temperature stated on the web, it's always good to exercise caution and cross-reference information from multiple reliable sources. While online resources can provide helpful information, it's important to ensure that the source is trustworthy and the information is backed up by scientific evidence or reputable references.
As for the description of the "first drop of liquid," it might not always appear as a perfect drop due to varying factors such as the compound's physical properties and the experimental conditions. The description in books is often generalized to convey the concept, but it's important to focus on the change in the appearance of the compound from solid to liquid as an indication of the first drop.
2.) If you choose a solvent whose boiling point is higher than the melting point of the compound to be crystallized, it can lead to some challenges in the process.
When you dissolve a compound in a solvent for crystallization, heating is often involved to facilitate dissolution. If the boiling point of the solvent is higher than the melting point of the compound, there is a risk that the solvent will boil before the compound fully melts. As a result, the compound may not be able to dissolve completely, leading to incomplete crystallization.
To overcome this, you should generally select a solvent with a boiling point lower than the melting point of the compound. This ensures that the compound can fully melt and dissolve in the solvent during the crystallization process. Additionally, it's crucial to consider other factors such as solubility, purity, and chemical compatibility when choosing a suitable solvent for crystallization.
I hope this clarifies your questions. Good luck with your experiments!