Manual for Recrystallization Essay

This essay has a total of 2214 words and 15 pages.

Manual for Recrystallization






Instruction Manual
The purification process:
Recrystallization & Filtration

Jason Williams
09-13-00
NATS 4310
Table of Contents
Preface
Chapter 1 Equipment involved and preparation
Glassware and accessories
Proper sterilization of equipment
Safety precautions
Chapter 2 Setup procedure before purification
Equipment setup
Choosing of solvent
Chapter 3 Gathering of an unknown compound and the first step: filtration
Collection
Filtration
Repeat Filtration and Cleaning
Collection and measuring of crude sample
Chapter 4 Recrystallization process
Solvent addition
Induction of Crystals
Collection
Chapter 5 Evaluation methods for purity
Small scale test
More accurate tests
Chapter 6 Frequently asked Questions and trouble shooting
Index


Preface
To begin, the intent of this booklet is to give instructional advice. The instructions
given will provide a basis to allow an individual to perform the necessary task to undergo
the purification process. The design of the manual is to instruct students in a college
laboratory setting. In particular, the area of science that the manual will focus on is
Organic Chemistry. Students will be able to refer to this instruction guide throughout
the semester because this process will be put in use often. The purification process if
an essential part of chemistry, and the student must recognize its importance. Without a
purified product, many of the drugs on the market would not be on sale. Even though these
purification procedures are on a small scale, it will provide a starting point for those
who are just beginning Organic Chemistry. The skills needed to purify a product will come
with practice and help from the instructor, but this manual will give the initial
directions to help the student on purification. Once mastered, more techniques will help
the student to gain a product that is pure enough to put on the market.




Chapter 1

The Equipment involved and preparation

The first step in understanding any laboratory process is understanding the equipment
needed. Also, there is a need for the proper preparation of the tools needed before any
of the steps can begin.


Glassware and accessories

The main pieces of glassware needed to conduct the filtration and recrystallization will
be at least two 250ml flasks, a 100ml flask, and at least three 50 ml flasks. In
addition, a glass stirring rod and a case of micropipettes would be useful. For the
filtration procedure, a funnel with a rubber stopper, a trapper flask, and a small piece
of filter paper is important to have. There is also a need for vacuum hoses in the
filtration process as well. The student will also need a hotplate. The lab will provide
all the necessary pipes needed to setup a vacuum and also the air current needed later on
in the collection phase. Each lab will have different types of equipment, and it is the
students responsibility to understand and learn how to work each tool.


Proper Sterilization

For any experiment to have the proper results, cleaning and sterilization is critical part
of preparation. The best way to have the glassware cleaned is to steam clean the many
pieces in a autoclave or a dishwasher. This may be done in advance by the instructor or
the students. It is also good practice to clean the equipment by hand, even after it has
come out of a machine cleaner. The funnel and the filter paper must also be free of any
impurities so that it will not reflect in the result. Because the purification process is
so important, there has to be a high standard of cleanliness for all the tools that the
student will use.

*It is extremely important that the student make sure all the pieces are dry as well or
the weight of excess water will show up in the results. Thus exaggerating the final
calculations*


Safety Precautions

Above all else, it is important to take all the proper methods to be safe in the
laboratory. All Students must wear safety goggles at all time in the lab. It would also
be a good idea to wear pants and shoes in case of spillage. Also, the student might also
consider wearing gloves, but the instructor will notify the student if the chemicals
require a student to wear gloves. It is also important that all safety related issues be
reported to the instructor immediately.

WARNING: DO NOT TRY TO CLEAN UP CHEMICALS WITHOUT NOTIFYING THE INSTRUCTOR



Chapter 2
Setup Procedure before purification

The setup for the process is simple, but choosing the right solvent to do the job is critical.

Equipment Setup

The setup of the glassware for the filtration procedure is as follows. First one hose
must be firmly on the vacuum pipe on the water facet in the lab. The other end of the
hose will go to a flask will connect to the top end of a trapper flask. ( The purpose of
the trap is prevent water from the pipe to flow into the filtrate after the process is
complete.) Next the on the side of the trapper flask is a small projection for another
hose. The other end of this hose will go to the 250ml flask with the vacuum projection on
the side. This is the flask where the filtrate will fall into. Place a funnel with a
small piece of filter paper in on the top of the flask. Make sure a rubber stopper is on
the top of the flask as well in order to have a proper seal. The only other setup
required is for the air drying process that is done in the collection phase after
recrystallization. A micropipette attached to a hose, which will provide a stream of air
to allow the solvent to evaporate off of the crystals. The air stream will come from the
pipes in ventilator hoods in the lab.


Choosing of Solvent

The most crucial part of any recrystallization is the need for the correct solvent. It is
important because it must dissolve the crude sample while it is hot but not when it is
cold. In addition, it must dissolve the impurities in the sample at both temperatures, so
that they remain in solution. This process is usually a matter of trial and error.
However, the instructor may have already chosen the solvent before hand. Students should
refer to their textbooks and understand the concepts of polarity and solvation before they
proceed to choose a solvent. *If problems arise ask the instructor for help.*



Chapter 3
Gathering of an unknown compound and filtration

Without proper filtration, the rest of the purification steps will be pointless. It is
crucial that the student take care when transporting the sample from each piece of
equipment to another.


Collection

The collection of the initial sample will come after the student has gone through the
desired experiment. Experiments that end in a final compound that is a mixture of solid
and liquid will require the filtration process. The collection of the compound will be
Continues for 8 more pages >>