Acetanilide Recrystallization experiment Essay Example

down the funnel and be present in the solution that was poured through the funnel. However some of the impure substances are small enough to be incorporated into the structure of the crystals in the funnel causing the pure material to consist of impure materials. For this, another round of vacuum filtration will be needed in order to ensure the most pure material is formed on top.Recrystallization is a useful technique but there are many problems that may arise during the experiment meaning this technique can be very time consuming. First of all, when the solute separates from the solvent it may not always be present in solid form. Instead of being solid, an oil layer can form in place.

When this happens there are various ways to resolve this. First of all, there is the addition of heated solvent using a pipet. Usually about 3-5 drops are added at a time to ensure that boiling still occurs. Sometimes when too much solvent is added a phenomenon called super saturation can occur which can be solved in one of two ways. Either the mixture can be boiled longer so that some of the solvent can be evaporated or a tool such as a microspatula could be used to stir up the mixture, allowing recrystallization to resume.In everyday life, application of recrystallization can be seen.

Some of these include the salt crystals in the saltshakers, sugar, and sucrose. In addition the microchips that are found in computers are made of silicon that has been processed through recrystallization. Recrystallization is also of growing importance in the pharmaceutical department. When recrystallizing certain types of drugs, the crystals themselves can display

different properties depending on the method to gain those crystals.

The crystals went into the filtration without the initial cleansing with water. After the initial few minutes of boiling the test tube, there was an oil layer that was seen. It was yellowish and seemingly caused the efficiently of the solubility to decrease. After the oil layer disappeared and the hot plate was turned off, the mixture seemed to be clear but almost instantly the test tube became encased in fog or what seemed like instant crystallization. However, there were actually no crystals present. After pouring through the filter paper that was present in the Buchner funnel, crystals were seen encased in a white sticky substance that probably resulted from not enough heating.

After the initial vacuum filtration, there was less of the white substance in the funnel most of it seemingly went through the funnel and present in the solution at the bottom of the Erlenmeyer flask. However, there didn't seem to be a sufficient amount of liquid that was present at the bottom probably due to me not boiling the mixture long enough or maybe not cleaning the crystals properly before doing the filtration. As expected from the second filtration, there was pretty much no crystals that formed. Not enough of the impurities came through the funnel, meaning that the initial crystals probably have been too large.The large crystals probably absorbed some of the impurities and those impurities became incorporated into the structure of the crystal itself. Without crystals being produced, in order to find a weight and percent recovered, the impure crystals from the first filtration were weighed.

From there the melting point was recorded,

which is when the first droplets appears on the substance until it turns completely liquid, turned out to be around 100-110 degrees Celsius.DISCUSSIONJudging from the lack of crystals that formed from the second filtration, something must have gone awry from the beginning when the test tube was being boiled. Probably the solvent either did not reach the boiling point when it was taken out or too much solvent was added to try to reduce the oil layer that kept forming. Adding around fifteen drops probably caused the solution to be supersaturated. And a seedling wasn't done to try to cause the solution to try to recrystallize so it remained in that stage with nothing really being produced. If the problem was too much solvent being added the test tube could have been heated longer to reduce the solvent through evaporation.

The crystals on top of the Buchner funnel from the initial filtration were approximately longer than 2mm meaning impurities must have been incorporated into the structure instead of following the solution into the Erlenmeyer flask. One of the impurities that remained was sodium sulfate. The melting point that was found was around 100-110 degrees Celsius, which is a decent amount lower than the actual melting point of 114.3 degrees Celsius.This was due to the fact that the impure crystals consisted of water and sodium sulfate, which reduced the melting point causing the error to occur. The flask also was not cooled to room temperature before placing in the ice bath which might have caused the formation of the crystals to become an even slower process than it needed to be.

If the flask was placed into the

ice water bath after cooling to room temperature the crystals might have been more prevalent and seeable to the naked eye. The percent recovered was not 100 percent instead it was a mere 7.2 percent. Some of the crystals might have been lost when transferring the hot liquid into the Buchner funnel.

Too much of the solid might have been dissolved while boiling the solution and the negligence of making sure to not let the solution boil too long.There were a lot of errors that occurred in the experiment that could've been avoided if more precautions were taken. For example, when seeing the oil layer, there was no need to put an excessive fifteen drops; instead around 3-6 drops should be enough to ensure the solution is usable. When the solution became cloudy within the test tube, the heat should've been left on until the solution became clearer and trustworthy to use. The crystals should've been cleansed with water before attempting to do the second filtration.

That way more of the impurities would've gone along with the rest of the solution through the filter into the flask.This lab shows that being careful is important. One simple change in the procedures will truly alter the outcome of the product to deviate from the standard by a lot. If the solution is boiled too much there will be too little solvent to work with, too much solvent will cause the solution to be supersaturated meaning that agitation of the solution will be needed to cause recrystallization to occur once again.

The flask needs time to cool to room temperature before being placed into the ice bath to allow a few

of the crystals to form instead of hindering the formation for quite a while.For this experiment the melting point should be considerably close to the melting point of 114 degrees Celsius if not impurities such as sodium sulfate and the remaining water in the crystals has lowered the melting point. When doing the second filtration, there should be a few crystals on top, if not then the solution wasn't filtered enough from the first filtration.