A. General Safety and Emergency Handling

LABORATORY SAFETY

Laboratory safety is of the utmost importance to anyone who does laboratory work. As a beginning chemistry student, part of your education in the undergraduate laboratory this semester is to learn to recognize that chemistry laboratory is, indeed, a very dangerous place where serious accidents do happen. This is not to discourage you from working in the laboratory. Instead, you must learn to be a responsible laboratory user who always works safely in the laboratory to avoid endangering yourself and others around you. You must constantly exercise your common sense.

A. General Safety and Emergency Handling

There are numerous safety precautions that you must undertake and safety regulations to remember. Your own diligence and your compliance to the instructions provided inside this Manual and by your laboratory instructor and demonstrators are required.

First of all, treat all chemicals as potentially hazardous. Most organic compounds are flammable and should never be heated with a Bunsen burner. Avoid inhaling chemical vapors, and learn the proper use of a fume hood for this purpose. Take special care when handling strong acids, bases, and bromine. Chemicals needed for your experiment are normally stored under designated fume hoods. Take only small amounts and return to obtain more when necessary.

If chemicals spill onto your skin (most likely your hands), wash the infected area under running water continuously for at least 15 minutes. Use the eye-wash (at least 15 minutes) if chemicals splash inside your eyes. Chemical spills on the bench-top or floor must be reported so that the proper course of action can be determined. Indeed, report all accidents (such as spills, cuts & burns, etc.) to your laboratory instructor or demonstrators, no matter how minor.

You must also learn the locations and basic usage of the fire extinguishers and fire blankets inside the laboratory. Know where the exits are in case it becomes necessary to evacuate the laboratory. In this respect, laboratory stools are not allowed to be placed in front of the fumehoods. Tripping accidents may result not only during practical sessions but also these stools pose serious obstructions during an emergency evacuation.

Secondly, keep your workstation and all common areas in the laboratory clean and tidy at all times. Students knocking off with their arms glassware placed dangerously close to the edge of the bench-top are common. Tripping from unseen objects on the floor (such as stools placed randomly in a narrow aisle) is another common accident. Also, the laboratory floor must be kept dry to prevent people from slipping. Water spills should be mopped up immediately. In case you break some glassware, never pick up broken glass pieces with your bare hands. Instead, ask your laboratory instructor or demonstrators for proper instructions.

At the end of an experiment, all apparatus must be cleaned properly and returned to where you obtain them. Wash your hands thoroughly before leaving the laboratory.

Most serious cuts result when glassware shatters while it was being forced into rubber tubing, plastic tubing, or stoppers. Pushing stoppers down the necks of flasks is also a dangerous act. Cuts can be avoided by taking the following precautions:

-When inserting glassware into rubber tubing, rubber stoppers, or corks, make sure that the hole in the stopper or cork is of the correct size. Always lubricate the glass with a drop of water or glycerol.

-When inserting glassware into plastic tubing, always soften the end of the plastic tubing by dipping it into hot water for a few seconds.

-Always use two hands for these operations and keep your hands practically touching.

-Always rotate the glassware or the stopper while pushing gently. In other words, screw the glassware through the stopper, or into the tube, and screw stoppers into flasks.

-Additional protection may be obtained by wrapping several layers of cloth around the glass before gripping on it.

B. Safety Regulations (Department of Chemistry)

LABORATORY USAGE No student is permitted to work inside the laboratory unless your instructor or demonstrator is present.

SAFETY GLASSES THESE MUST BE WORN AT ALL TIMES IN THE

LABORATORY.

DRESS PROPERLYLong pants for men and full-length dresses or slacks for

women must be worn. Shorts and mini-skirts are not

allowed. You must wear closed-toes shoes. No sandals are

allowed. Long hair should be tied back.

CONTACT LENSES Do not wear your contact lenses in the laboratory. They

may trap chemical vapor inside your eyes and make eye

injuries more severe.

FOOD You must not eat or drink inside the laboratory. No

smoking or applying make-up is allowed.

WASTE DISPOSAL Chemical waste must be disposed of properly in designated

waste containers only. Consult this Laboratory Manual and

your instructor or demonstrators for more instructions.

For up-to-date laboratory safety information from the Purchasing, Safety & Security Office (PSSO) of the Department of Chemistry, visit

C. Handling Apparatus with Glass Joints

Many of the apparatus that you will be setting up to run organic chemical reactions, etc., involve glass joints. The following paragraphs provide you with an introduction to these glass joints and the proper techniques to handle glassware in general.

Quickfit and Clearfit Glass Joints

Until the first quarter of last century, assembling laboratory apparatus often involved the use of corks, rubber bungs, rubber tubing, and glass tubing. It was often difficult and time consuming. A noteworthy improvement came in the early 1930s when the ground glass conical joint was introduced commercially. In describing glass joint, we use the term “cone” for the part that is inserted and “socket” for the part into which the “cone” is inserted. By means of grinding, glass cones and sockets were made to such precise limits that they could be fitted together quickly to make effective joints. Hence, the trade name Quickfit came about. Ground glass conical joints, however, had certain limitations because once the original smooth surface of the glass was damaged enough by grinding, the advantage would be lost.

Later, improvement in the production process enabled the manufacturing of a new range of laboratory apparatus with clear glass conical joints. They retain the original smooth glass surface even after repeated uses and are known by the trade name Clearfit. Common joint sizes are B14, B19, B24, B29, and B34 in order of increasing diameter of the joint.

Care of Glass Joints

All glass joints should be kept completely free from dirt. Dust in a glass joint may cause leakage and grit may even cause breakage. Therefore, before use, glass joints should be wiped free from foreign matter. After use, joints should be separated as soon as possible, preferably while still warm to prevent seizure.

Seizure of Glass Joints

Seizure of Quickfit ground conical joints may be due to cementation. Sodium hydroxide should never be allowed to remain in contact with the ground joint surface. It attacks the matt surface very rapidly and the products of the attack, if left between two ground surfaces, will cement together. Jamming may also cause seizure. Although Clearfit glass joints are less prone to seizure, it is necessary to exercise similar precautions when handling them.

Lubrications

For work under atmospheric pressure, lubricant is normally not required. Lubrication of the ground joints with grease is essential, however, when conducting distillation under reduced pressure or when there is possibility of basic solution coming into contact with the ground glass surface. Petroleum jelly or silicone stopcock grease can normally be applied, but silicone high vacuum grease is necessary for best result. Excess grease will contaminate reaction products and such must be avoided. When using a silicone grease, care should be taken to ensure that jointed equipment is not left assembled for any length of time as “dry out” of the lubricant may occur causing seizure of the joints.

Clamping of Quickfit or Clearfit Glassware

Supporting rather than clamping forcefully should always be the first principle in assembling glassware. Clamps should only be tightened to fingertip-tightness (i.e., not too tight). Before tightening the clamps to the stand, it must first be ascertained that the apparatus is free from physical strain.

Cleaning and Care of Glassware

Clean apparatus is essential for laboratory work. If grease is used to lubricate the glass joints, the joints should first be carefully wiped clean with tissue paper, and the remaining grease then removed with cotton and wool containing ether or chloroform. After that, the glassware should be washed properly with detergent. If washing up is done immediately after an experiment, it is nearly always possible to remove organic compounds from glass apparatus. If a brush is used inside the flask, avoid scratching the glass with the metal parts. Tarry residue may be removed by the use of dichromate cleaning mixture. Glass apparatus is best left to drain dry in a rack or it may be dried in an oven.

Care should be taken to avoid scratches on the surface of glassware as these will reduce the mechanical strength of the glass and make it more susceptible to breakage through thermal shock. Proper cleaning and storage of flasks will lengthen their life significantly. Scratches sufficient to cause breakage are produced often by unprotected glass stirrers, rubbing or knocking two flasks together, or by the metal stems of cleaning brushes. The technique of scratching a glass vessel to induce crystallization should never be attempted in Quickfit or Clearfit flasks.

TECHNIQUE 1. Extraction

Extraction is a commonly used separation technique for separating a desired compound from a mixture or from impurities. A separatory funnel is necessary for a liquid-liquid extraction, which is outlined in the following steps:

Practice opening and closing the Teflon stopcock with an empty separatory funnel while holding the funnel in the correct position with both hands as shown in the figure below. Note that it is very important for you to use your index finger to hold the glass or plastic stopper tightly in place.

Now, MAKE SURE THE STOPCOCK IS CLOSED. Place the funnel upright in an iron ring attached to a ring stand. Remove the stopper and pour into the separatory funnel (with the aid of a glass funnel) the solution to be extracted. Add also the extraction solvent.

Note: The total volume of the solution inside should be NO MORE THAN 2/3 of the volume of the separatory funnel.

Replace the stopper. Hold the filled separatory funnel using the correct position with both hands like before. Carefully invert the funnel a few times and then slowly open the stopcock to release any built-up pressure. Close the stopcock afterwards and shake the funnel for several seconds. Vent, and shake again. Vent, and shake one more time. Vent once again before returning the funnel to the upright position in the iron ring.

Remove the stopper and allow the layers to separate.

To capture the bottom layer, open the stopcock gradually and drain it into a clean container (a conical flask). Close the stopcock as soon as the last trace of the bottom layer has gone down and out of the funnel. Over-draining is not uncommon; however, it should be avoided if at all possible.

Remove the upper layer by pouring it out from the top of the funnel (into a beaker). This way it will not become contaminated with traces of the lower layer found in the stem of the funnel.

Note: Make sure you know which layer is aqueous and which is organic. Usually, the bottom layer is organic. Ether, for example, is a solvent that is less dense than the aqueous layer.

The organic layer, at the end, should contain only the organic compound. However, there might still be traces of the aqueous solvent, or water, inside. Therefore, you should add a drying agent (anhydrous magnesium sulfate MgSO4) to the conical flask containing the organic layer to absorb any residual water. Allow about 10 minutes for drying. The hydrated (wet) MgSO4 can then be separated by simple filtration.

TECHNIQUE 2. Folding a fluted filter paper

TECHNIQUE 3. Simple Distillation

Distillation is also a separation technique. Distillation differs from reflux only in that at least some of the condensate is removed from the boiling system. The mixture, which usually contains two components, is heated and the temperature of the vapor is maintained at boiling point of the lower boiling liquid, throughout the simple distillation.

Set up the distillation according to the diagram on the next page. The distilling flask should contain the mixture with a few boiling chips. The receiving flask may be a conical flask.

Check to make sure the cooling water is running properly in the condenser before starting to heat the mixture.

While there is no need to watch the temperature of the water bath (the heat source), the temperature reading of the thermometer should stay steady at about the boiling point of the lower boiling component of the mixture when liquid begins to emerge at the other end into the receiving flask. This is because the vapor above the mixture should contain mostly the lower boiling liquid.

Note: While we want to continue heating until the last drop of liquid emerges, always keep an eye on the distilling flask because it is dangerous to heat the flask until its content is completely empty.