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Glass Care and Maintenance

When treated with proper care edutek laboratory apparatus will give a long and satisfactory service. The following prepared notes are to assist users in obtaining the maximum life and performance from their
apparatus. Our sales department will be happy to advise on any aspect concerning the safe use of our products.

HEATING AND COOLING

Glass may suffer damage in three ways:

» It may break under thermal stress in the steady state, that is when there is established constant thermal gradient through the glass.
» It may break under the transient stress of a 'thermal shock', that is sudden heating or cooling.
» It may, if heated beyond certain temperature, acquire a permanent stress on cooling which could cause subsequent failure.

The following precautionary measures will assist in avoiding failures during heating and cooling procedures.

1. Never leave vessel unattended when evaporation work is being carried out. The vessel may crack or explode as dryness condition is approached if the heat source is not adjusted correctly. Lower the temperature gradually as the liquid level drops.
2. Always use caution when removing glassware from a heat source and avoid placing on a cold or damp surface. Although the ware can withstand extreme temperatures, sudden temperature changes may
cause the vessel to break.
3. Always cool vessels slowly to prevent thermal breakage.
4. Never apply heat to badly scratched or etched vessel as the thermal strength will have been greatly reduced.
5. Never apply point source heating to a vessel as this will greatly increase the chance of breakage.
6. Always diffuse the heat source by using a metal gauze or air/water bath. Alternatively ensure even heating of the vessel by slow movement of the vessel in relation to the heat source.
7. Adjust Bunsen burner to get a large soft flame. It will heat slowly but the mechanical and thermal strength of the vessel.
11. Thick walled glassware should not be subjected to direct flame or other localised heat source. Vessels of this type are best heated with the use of an electric immersion heater.
12. Avoid heating glassware over electric heaters with open elements. Uneven heat of this type can include localised stress and increase the chance of breakage.
13. Remember that the hot plate will retain heat long after the appliance has been switched off .
14. Always ensure that the surface of the hot plate is larger in area than the base of the vessel being heated. An under-sized plate of the job in hand will invite uneven heating and promote breakage of glassware.
15. Always ensure that manufacturer's instructions are Bollowed when electrical heat sources.

Mixing and Stirring

1. Always use a policemen's or similar device on stirring rods to prevent scratching the inside of a vessel.
2. When using a glass vessel with a magnetic stirrer always use a covered follower to prevent abrading the inside of the vessel.
3. When using glass or metal mechanical stirrer in a glass vessel always predetermine the height of the stirrer before use to ensure there is no contact between the stirrer blade and the bottom or sides of the vessel.
4. Never mix sulphuric acid and water inside a glass measuring cylinder. The heat of reaction can break the base of the cylinder.

Vacuum and Pressure

1. Never use a glassware beyond the recommended safe limit.
2. Always use a safety screen when working with glassware subjected to pressure of vacuum,
3. Never subject glassware to sudden pressure changes. Always apply and release positive and negative pressures gradually Joining and Separating glass apparatus useful in aiding separation.
5. In using lubricants it is advisable to apply light coat of grease completely around the upper part of the joint. Use only a small amount and avoid greasing that part of the joint which contacts the i nner part of apparatus.
6. Three type of lubricants are commonly use on standard taper joints
(A) Hydrocarbon grease is the most widely used. It can be easily remove by most laboratory solvents, including acetone.
(B) Because hydrocarbon grease is so easily removable, silicon grease is often preferred for higher temperature or high vacuum applications. It can be removed readily with chloroform.
(C) For long term reflux or extraction reactions, a water soluble, organic and insoluble grease, such as glycerin, is suitable. Water will clean glycerin. There are other type of greases which can be used specifically when certain reagents are used in the Burettes or Separating Funnels.
7. The use of water, oil or glycerol is recommended on both tubing and rubber bung when inserting glass tubing into a bung. Always wear heavy protective gloves or similar protection when carrying out this operation.
8. Always fire polish rough ends of glass tubing before attempting to insert into flexible
tubing. The lubricants recommended above may also prove useful.
9. Never attempt to pull a thermometer out of a rubber bung. Always cut the bung away. PERSONAL SAFETY
1. Use tongs to asbestos gloves to remove all glassware from heat. Hot glass can cause severs burns.
2. Protective gloves, safety shoes, aprons, and goggles should be worn as safety chemical accidents, spilling or splattering.
3. Always flush the outside of acid bottle with water before opening. Do not put the stopper on the counter top where someone else may come in contact with acid residue.
4. Special care is needed when dealing with mercury. Even a small amount of mercury in the bottom of a drawer can poison the room atmosphere. Mercury toxicity is cumulative and the element's ability to amalgamate with a number of metals is well known. After an accident involving mercury, the area should be cleaned carefully until there are no globules remaining. All mercury containers should be kept well stoppered.
5. Never drink from a beaker. A beaker left specifically for drinking is a menace to the laboratory. Do not taste chemicals for identification. Smell chemicals only when necessary and by waiting a small amount of vapour towards the nose.
6. Avoid pipeting by mouth, particularly when using concentrated acids, alkalis or potentially biohazardous materials. Use mechanical means such as a rubber bulb or an automatic
10. Spattering from acids, caustic materials and strong oxidizing solutions on the skin or clothing should be washed off immediately with large quantities of water.
11. When working with chlorine, hydrogen sulphide, carbon monoxide, hydrogen cyanide and other very toxic substances, always use a protective mask or perform these experiments under a fume hood on a well ventilated area.
12. In working with volatile materials, remember that heat causes expansion and confinement of expansion results in explosion. Remember also that danger exists even though external heat is not applied.
13. Perchloric acid is especially dangerous because it explodes on contact with organic materials. Do not use perchloric acid around wooden benches or tables. Keep perchloric acid, wear protective clothing.
14. When using hot plates and other electrical equipments, ensure the wire and plugs are in good condition. Never handle Electrical connection with damp hands.

CLEANING

Successful experimental results can only be achieved by using a clean apparatus. In all instances laboratory glassware must be physically clean, in nearly all cases it must be chemically clean and in specific cases it must be bacteriologically clean or sterile. There must be no trace of grease and the safest criteria of cleanliness is the uniform wetting of the glass surface by distilled water-this be ing of the utmost importance for glassware used for volumetric methods. Any prevention of uniform wetting of the surface will introduce errors such as distortion of the meniscus and accuracy of volume.

GENERAL CLEANING

1. Cleaning of glassware which has contained hazardous materials must be solely undertaken by experienced personal.
2. Most new glassware is slightly alkaline in reaction. For precision chemical tests, new glassware should be soaked several hours in acid water (1 % solution hydrochloric acid or nitric acid) before washing.
3. Glassware which is contaminated with blood clots, culture media, etc. must be sterilized before cleaning.
4. If glassware become induly clouded or dirty or contains coagulated organic matter, it must be cleaned with chromic acid cleaning solution. The dichromate’s should be handle with extreme care because it is a powerful corrosive
5. Wash glassware as quic kly as possible after use but if delays are unavoidable, the articles should be allowed to soak in water.
6. Grease is removed by weak sodium carbonate solution or acetone or fat solvents. Never contamination on the glassware.
10. Special type of precipitate material may required removal with nitric acid, aqua regia or fuming sulphuric acid. These are very corrosive substances and should be used only when required.
11. It is imperative that all soap detergents and other cleaning fluids be removed from glassware before use. This is especially important with the detergents, slight traces of which will interfere with serologic and culture reactions. After cleaning, thoroughly rinse with tap water ensuring that containers are partly filled with water, shaken and emptied several times. Finally rinse with deionised or distilled water.
12. Drying can be undertaken either in baskets or on pages in air or at a temperature not exceeding 120°C.
13. Always protect clean glassware from dust by use of temporary closures or by placing in a dust free cabinet. For cleaning specific type of glassware, please refer the following pages. Cleaning Specific Types of Glassware
1. Pipettes
Place pipettes tips down, in a cylinder or tall jar of water immediately after use. Do not drop them into the jar, since this may break or chip the tips and render the pipettes useless for accurate measurements. A pad of cotton or glass wool at the bottom of the jar will help to prevent breaking of the tips. Be certain that the water level is high enough to immerse the greater portion or all or each pipette. At a convenient time, the pipettes may then be drained and placed and in a cylinder or jar of dissolved detergent or, if exceptionally dirty, in a jar of chromic acid cleaning solution. After soaking for several hours, or overnight, drain the pipettes and run tap water over and through then until all traces of dirt are removed. Soak the pipettes in distilled water for at least one hour. Remove from the distilled water, dry the outside with a cloth, shake out the water and dry.
Burettes (with glass stopcock )
1. Remove the stopcock key and wash the burette with detergent and water.
2. Rinse with tap water until all the dirt is removed. Then rinse with distilled water and dry.
3. Wash the stopcock key separately. Before the stopcock key is replaced in the buretts stopcock key are not interchangeable
4. Always cover burettes when not in use.

Culture Tubes

1. Culture tubes which have been used previously must be sterilized before cleaning. The best general method for sterilising culture tubes is by autoclaving for 30 minutes at 121°C (15ib. pressure). Media which solidify on cooling should be poured out while the tubes are emptied, brush with detergent and water, rinse throughly with tap water, rinse with distilled water, place in a basket and dry. sterile container. It may be expendient to sterilize all tubes as routine.
2. To clean and sterilize tubes containing blood, discard the clots in a waste container and place the tubes in a large basket. Put the basket, with others, in a large bucket or boiler. Cover with water, add a fair quantity of soap or detergent and boil for 30 minutes. Rinse the tubes and clean with brush, rinse and dry with the usual precautions.
3. It is imperative when washing serological glassware that all acid, alkali and detergent be completely removed, Both acid and alkali in small amounts destroy complement and in large amounts produce hemolysis. Detergents interfere with s e r o I o g i c reactions.
4. Serological tubes and glassware should be kept separate from all other glassware and used for nothing except serologic procedures.

 
 
 
 
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