Lab Set-Up & Safety
by K9girrl and The Real
Lab Set-Up & Safety
This was written mostly by K9girrl, but some of it was written by The Real. This is a wonderful write up on setting up a lab and safety in the lab. This will be updated when ever K9girrl adds more.
This is the first of an on-going series on simple Lab. setup and techniques. I will post each section as I have time, so watch for them. Wherever possible I will suggest pieces of home hardware that can substitute for "official" lab-ware. I shall start with the basics and work up to special methods for organic chemistry. CHEMHEAD and others please feel free to comment and post any information that I have missed.
SAFETY: Leather work gloves are essential for cutting and bending glass tubing. To protect yourself from chemical splashes you need plastic apron, safety glasses, and sometimes rubber gloves. Speaking of splashes ALWAYS pour acid into water, slowly while stirring. NEVER pour water into acid as it may bubble and splash you.
LOCATION: You should locate your lab out of sight, but with excellent ventilation. In front of an upper floor openable window is ideal. loose drapes can be a fire hazard, a roll-down blind is better. Install on the window sill a small hook for the pulldown string, so that blind won't flap in the breeze. Venetian blinds are OK, except in strong winds. Any exhaust fan should not have sparking 'brushes" in its motor, these could ignite volatile vapours. Gas for the Bunsen can come from a portable propane tank hung outside the window like a flower box. Propane leaks will thus be outside the building. You will need running cold water and a drain pipe, also one or two electric outlets.
BENCH: Your work table (called a "bench") should be belt buckle high or a bit more. The bench may be raised by stepping each leg onto a brick or a cement block. It should be strong, able to support about a 100 lbs. safely - you do NOT want chemicals and flame dumped onto the floor. Hardware stores have various metal angle braces that go on with wood screws. You might get elaborate and install a small bar-style sink hooked up with rubber hoses. If you do this the faucet should have a high curve gooseneck, and a graduated "hose barb" on the wet end. This fitting is useful for feeding a distillation condenser by means of soft rubber tubing,
STORAGE: Install extra strong shelves near the bench but not over it. It is hazardous to reach over working apparatus for the next bottle of chemical! An old cupboard with locking doors is ideal for dangerous chemicals such as acids. A strong horizontal board with upwards angled finger-thick pegs (about 4 to 6 inches long) makes a good drying and storage rack for flasks. This resembles an old style coat rack, but is mounted head high on the wall. Liquid chemicals are stored in pourable bottles, dry or paste chemicals in wide mouth jars; all with tops on of course. Empty any bags or boxes of dry chemical into clean dry jars. these new containers must be clearly labeled with a band of packing tape and waterproof felt pen. Both container and top should not react with the chemical. Certain chemicals (such as silver compounds) are light sensitive and need a dark coloured container.
WASTE DISPOSAL: Never mix waste paper or rags with chemicals in an INDOOR waste basket. Some combinations are a fire hazard. Never sweep broken glass crumbs with hands, use a whisk and dust pan. Solid chemical waste can usually be put down a sink NOT fitted with a garbage disposal machine. flush down with lots of water. Waste acids may be neutralized in an earthenware crock half-full of broken up oyster or clam shells or marble stone chips. carbon dioxide will bubble up, when bubbles stop, drain off liquid and flush down drain with lots of water. Inflammable liquids do NOT go down drain, but pour out onto vacant land away from buildings, gardens, grass or trees.
LAB WARE: Glass is two types, "soft" or lime glass that can be re-shaped at home in Bunsen flame. "Hard" or pyrex glass is very heatproof, but cannot easily be reworked into different shape. Most flasks and beakers are "hard" glass but must be heated on asbestos wire-gauze pad, not over naked flame.
Glass Tubing: The common size 6MM O.D. glass tubing should be purchased 'soft" except for special applications such as the "hard" central tube in a distillation condenser. a couple of pounds of 6MM out side diameter (not bore size!) "soft" tube should last you for years. Hold "soft" tube with leather gloves and heat bend spot bright red with fan-shaped flame spreader on propane torch. a wide-wick kerosene lamp (no chimney) loaded with methyl alcohol will work. Practice to judge the correct bright red heat on about 2 inches of tube, then bend your angle. Place on heat proof surface to cool-BEWARE! it will be very hot even when glow stops. To cut glass tube, score crosswise with new sharp triangle file. Be sure to put some sort of handle on the pointed file tang. Hold tube either side of score in leather gloves -wear safety glasses- and bend the tube away from the score. The sharp cut ends are smoothed (flame polished) by simply heating past bright red to slightly molten.
Rubber Tubing: You need perhaps 10 to 15 feet of soft rubber tube that can be pushed over your glass tube. A drop of glycerine will lubricate the fit. There are tiny adjustable clamps called "pinch cocks" that can stop or regulate the flow through a rubber tube. There is a clear plastic lab tube called TYGON that is quite good, but does not "pinch" as well as rubber. The ends of plastic tubing are dipped into hot water just before fitting.
Cleanliness-practice it like your a religous fanatic, concerning labware, work areas, the floor, and of course yourself. Organic chemicals have the nast tendency of being readily absorbed through skin. Yes you should wear gloves, but that does not stop everything.
Know your chemicals, have an MSDS for everything you have, know how to use the MSDS, and have proper supplies for suppressing fires and cleaning spills.
Absolutely no food or drink in the lab whatsoever, no smoking, or drug use for that matter.
If possible transfer liquids via pippette or containers specifically designed for pooring (ie tip container, self dispensing, or able to use TFPE/glass stopcocks), this will eliminate spills and does allow for accurate measuring. To help reduce the risk of splashing Erlenmeyre flasks are great, but don't use if you expect a large amount of foaming.
Rubber Stoppers: When a stopper is TIGHT in the flask, nearly 1/3 should protrude. Plain fine grained cork is easier to drill, but rubber usually lasts longer and is less reactive. It is easier to buy 1, 2, and some 3 hole rubber stoppers as rubber is difficult to drill neatly. The correct drill for rubber has a sharp concavity; rather than a sharp point as in a normal twist drill. It is just possible to twist-drill rubber a 1/4 inch at a time by frequently lubricating the bit with damp bar soap. The stopper is gently held in pliers with ( ) shaped jaws. A drill press (medium speed, slw feed) really helps keep your hole straight and plumb. The drill bit should be about 3/4 the diameter of the glass tube. Lube stopper hole and tube with a little glycerine and wear leather gloves while twisting the tube into the hole. Never try to use the bent portion of a glass tube as a lever, as it will break. never try to insert glass tube while stopper is in a flask. If a tube is left in a stopper for some time, it may become stuck there. This is OK for permanent apparatus like wash bottles and distillation heads. Home brewery/wine-making stores have large diameter rubber stoppers that may fit old pyrex glass coffee pots.
Test Tubes: these are for testing reactions while using a minimum of chemicals. Typically there will be a row of them with slight variations in contents, to compare the effect of these small changes. They come in either "soft" or "hard" glass. The 'hard" of course stand heating better without breaking. perhaps the best size for home use is 1/2 to 3/4 dia. and about 6 inches long. The Chemical type has a pouring lip, the Biological type has no lip. There are small tongs available to hold hot test tubes. a test tube rack is easily made from scrap wood.
Beakers: These are 'hard" glass cylindrical cups with a pour spout and often milliliter volume calibrations. A group of different sizes can be nested together on a shelf say 50ml., 100ml., and 250 ml. there are kitchen pyrex measuring cups in several larger sizes up to 1/2 gallon. Note that a milliliter is "close enough" to a cubic centimeter C.C.
Flasks: These are "hard" glass but are not heated over naked flame because of breaking risk. There are two main types: "Florence' round bulb with small flat bottom. Used mainly for INDIRECT heated setups, such as water or sand bath over the Bunsen. "Erlenmeyer" has a conical bulb with large flat bottom, used in DIRECT heated setups with flask perched on wire gauze / asbestos pad over Bunsen. The necks are available in different diameters. For stoppers with multiple holes, or with a fractional distillation tower through a single large stopper hole; then a wide neck is necessary. The neck of a flask should be padded with asbestos or glass-fiber cloth whilst supported in a retort clamp. Otherwise the expanding hot glass may be cracked by the clamp.
Stands, Rings and Clamps: One useful stand is a inch diameter iron ring set about 8 inches high on tripod legs. These were intended to hold clay flower pots. A friend with a torch to do bronze-welding can make you retort stands, rings and flask clamps out of angle iron and Re-bar rod. From a Lab supply buy several wire-screens with asbestos center discs. These are called lab gauze, never heat beakers or flasks over naked flame.
Funnels: You need at least one glass funnel with a long stem. The most common size takes 11 cm. diameter filter paper formed into a cone. This is used for "through the stopper" applications on flasks. I have a white nylon long funnel that is quite good for most things. You must use filter paper, as regular papers are coated and do not work. Fold your disk of filter into quadrantal segments. One of these segments is folded across to overlap into a cone of paper. This fits well enough the 60 degree funnel cone. The household coffee filter funnel works for large volume filtration into beakers or jars. This funnel has a shoulder to make it perch on the rim of the receiving vessel. They come in single cup or whole pot sizes, use the ones that take filter paper not metal screen. The specialized "thistle tube" funnel is not used for filtration but for "through the stopper" direct introduction into flasks such as gas generating apparatus. There is also a "separating funnel" with a ground glass valve useful for adjusting the drip rate into a flask. Some of the esoteric branches of organic chemistry use filter funnels with most of the spout removed to prevent deposits condensing in the spout. Still others involve glass funnels warmed by sheet copper hot-water jackets!
Porcelain Ware: There are many small porcelain dishes from Oriental stores that will substitute. For example I have a suction flask made of a small Japanese teapot! The rubber suction hose goes over the narrow spout, a wide rubber stopper from Wine-Arts carrys the filter funnel and replaces the lid of the pot.
MEASURING: It is possible to make a two-pan balance with coiled bits of copper wire for weights. You will need to borrow some standard weights to calibrate the wire. A graduate column will be necessary for liquid volumes, and may also float a hydrometer for Specific Gravity (S.G.) measurements. You might need one or two pipettes for routine small volumes. Later I will explain simple "glass blowing" to make pipettes, but you will need a good one to calibrate the homemade. Some stick-form thermometers may be necessary, select them to clearly show the temperature ranges that interest you. A single all-purpose thermometer will not display small variations in temperature. I will explain this in the Distilling section where it becomes critical to hit correct boiling points (B.P.)
Keep the copper coil weights in a solvent to keep them free of oils and other organic chemicals. Also try to use good enameled wire to prevent oxidation. Calibrate at least 6mos and replace as necessary. MW35 18ga copper wire works great for such applications.
This is the second part of basic chemistry series. We will cover solutions, filtration, crystallisation, and several kinds of distillation.
SOLUTIONS: Solutions are two parts; the solvent and the solute.The solvent is the dissolving fluid, and the solute is the sobstance dissolved therein. Common solvents for Organic chemistry are: (single solvent class I) water, alcohol, ether, Ligroin (petroleum ether) , glacial acetic acid, benzene. (mixed solvents class II) water+ alcphol, water + glacial acetic acid, ether + Ligroin, and benzene + Ligroin. There are 3 ways of expressing solution; Percentage, Molar, and Normal.
Percentage Solutions: There are two ways to express percent solutions; percent solute by volume, and percent solute by weight. In the first way both liquids are measured by volume. In the second way both liquid and dry are weighed. To weigh a liquid, subtract the empty container weight from the weight of container + liquid. Molar Solutions: These are based on the molecular or Formula Weight of the solute. This weight is found by adding (the atomic weights using a table) of chemical elements in a typical solute molecule. M solutions are seldom prepared, and in many cases the solute will not dissolve in the theoretical amount of solvent. Fractional Molar solutions are thus more common, for example; M/4 meaning 1/4 gram formula weight per Liter of solution. Other examples are: 0.1M or M/10 each meaning 1/10 gram formula weight of solute per liter of solvent.
Normal Solutions: This is the most common expression of solution. The advantage is that equal quantities of reacting solutions having same normality N will combine with no left over waste. ( I can't enter the simple equation on this one line entry.) In simple practise Normal Solutions are prepared using Equivalent Weights table rather than formula weight.
DISSOLVING the SOLUTE: Using water, glacial acetic acid, or not easily inflammable solvents, these may be heated in flask on wire-gauze pad over direct flame. Frequently stir or shake the flask to dissolve crystals on bottom, lest heat difference may break the flask. Flammable alcohol and benzine may also be heated on wire-gauze over direct flame if small quantities are used. ......
Dont forget solvents such as dichloromethane (DCM, methylene chloride), toluene, chloroform (trichloromethane), acetone, nitromethane, nitroethane etc.
....If it ignites do not blow on it, but remove from flame and snuff flask with glass cover such as inverted small beaker. For large quantities of alcohol, benzine, ether, ligroin, carbon disulphate or other low B.P. (boiling point) solvents they are heated indirectly in flask nested in sand or water bath. These are supported metal bowls of water or dry sand surrounding a Florence flask. The bowl is heated from beneath by a bunsen. The flask stopper should have thick vertical glass tube to act as air cooled condenser and to spout vapour much higher than the flame. If the solvent is not miscible (mixable) with water, then the solute should be dried of water before adding to the flask. To achive the best crystallisation later, use ONLY ENOUGH solvent. Start with too little solvent to dissolve, and after heating add just enough new warm solvent for the stirred solute to disappear. Upon later cooling you will have supersaturation yielding lots and lots of crystals. Sometimes a mixed solvent (class II) is used; one solvent which easily dissolves solute, and another solvent that dissolves it with difficulty. first dissolve in hot "easy" solvent, then add the hot "difficult" solvent. Sometimes the solute will not disappear completely when the correct amount of "difficult" solvent has been added. Do not spoil your chance of future crystallisation by being tempted to add more solvent, just leave the little bit of slute undissolved.
FILTRATION: A suitable funnel containing a cone of filter paper is supported over the receiving vessel, often a beaker. This receiver is often pre-heated a bit to avoid cracking if hot solution is used. The spout of the funnel should touch the inside wall of the receiver so that the liquid runs down the wall rather than falling. To pour into the funnel without tearing thin wet filter paper, pour along a vertical glass rod you hold touching the inside of the funnel. Do not touch the rod to the inside bottom of filter cone, lest you puncture the wet paper. for hot organic liquids, the funnel spout may be shortened to prevent condensation in the spout. There are small abrasive cut-off wheels for the Dremel power tool that can cut glass. There is a thin rapid-filter paper available. For large crude chemical work use coffee filter funnels, most of which are designed to perch on a jar rim. these coffee papers are strong enough not to need the glass rod pouring technique, but do pour slowly. If inflammable solvents are used, turn off flame and sources of ignition before pouring. Boiling nitrobenzine, analine, phenol, may be filtered using regular filter paper. Some acids may require a nitrocellulose filter. This material is explosive when dry, and is stored wet in a jar.
Only a few crystals should form in filter paper using HOT solvent. If lots of crystals form on paper whilst pouring, then too little solvent was used. You may elect to puncture the paper and return everything to the heating flask with a bit more solvent this time. It helps to keep records of amounts used so that future batches become easier. Remember you can easily have too much solvent! Sometimes differently soluble crystals will condense between paper and funnel wall. For large quantities you need a large glass funnel kept warm by a custom made hot water jacket. For small quantities, a pyrex funnel may be gently pre-heated over a flame just before filtering.
CRYSTALLISATION: The size and shape of the container influence crystallisation. generally a beaker is good, as long as it is 1/2 to 1/3 full. the mouth is then covered with a filter paper, then a large watch glass or plate. The paper insulates the glass cover preventing condensation. The beaker must be left UNDISTURBED in a cool place during crystallisation, say the back of the refrigerator. If crystals form slowly, "seed" the solution by throwing in a pinch of the correct crystals. A common mistake is that you get a melted-looking substance rather than crystals. This is because the solution was too concentrated. so it's back into the heating flask with more solvent this time. See why careful experimental records are important? When you win crystals you need to remember exactly why and how for next time.
SEPARATION: Now the crystals are to be separated from the liquid (mother liquor). It is not good practise to simply dump into filter because crusts on side and rim of beaker are considered impure for Organic purposes. Suck out the crystal strata with a meat baster (like a huge eye-dropper). This is gently squished into a filter that has been moistened with solvent. The crystals caught in the filter are gently spray washed with fresh solvent to remove the last traces of the mother liquor. a small flat bottomed coffee filter is better than a conical lab filter, in that it spreads the crystals out for washing. In this it resembles the special BUCHNER organic filter. Do not wash too much, and begin to re-dissolve! A gentle little mist spray is enough.
If your solvent will not evapourate easily in air (i.e. glacial acetic acid, toluene, nitrobenzene, etc.) these must be mist-washed off the crystals with a more volatile solvent: drain and mist with half-and-half original and volatile solvents. Now drain and mist with pure volatile solvent. Example: original acetic acid solvent may be displaced in this technique by distilled water that will air dry.
DRYING CRYSTALS: The damp crystals must now be dried 1. air drying, 2. gentle heating by warm air stream, 3. chemical drying. For air-dry the crystals are spread out in thin layer upon several thicknesses of filter paper and covered with a large inverted funnel. A bit of air flow is important, so the funnel rim is stepped up on thick slices of cork. Forced drying by GENTLE heat is tricky as crystal form may be damaged. Always test a small amount before committing the entire batch and perhaps spoiling it. Crystals not easily soluuble in ether but crystallise from a solvent muscible with ether; can be thus quickly air dried after ether misting.
SECOND "RUN" CRYSTALS: Some substances are easily soluble in ALL available solvents and will crystallise only on partial evaporation. A good crystallisation dish is the pyrex kitchen casserole with matching flat glas lid. For air flow but to keep out most dust; this lid is to be lifted up with cross rods (I use chopsticks across small dishes.) Sometimes to get good crystals you need very slow evaporation, and a filter paper covered 1/3 full beaker is used instead of an evap. dish. leave undisturbed for a long time.
The rim and sides of the crystallisation vessel may now be scraped down to dissolve in the mother-liquor. A second 'run' of crystals may often be obtained by evaporating a bit of the solvent. the liquor may also be diluted with a second solvent that does not easily dissolve the solute. Examples: a solution in alcohol or glacial acetic acid may be diluted with water; OR a solution in ether or benzine diluted with ligroin to force crystals out of solution.
EVAPORATION may be rushed by surrounding the beaker with a desiccant in an enclosed space such as a covered plastic bucket. For absorption of water and/or alcohol use calcium chloride surround (granulated or fused) or sulphuric acid. Glacial acetic acid is absorbed by soda-lime, solid potassium hydroxide, or with sodium hydroxide.....
..Dehydrated magnesium sulphate or fused sodium sulphate are sometimes used for drying. Crystal purity depends on impurities being left behind in the mother-liquor, so do not allow solvent to evap. completely. Your crystals must be suctioned out meat baster) while still covered by solvent. After filtering your abundant crystals are mist washed and drained as before. If you have only tiny amount of crystals from small batch, spread them on clean dry unglazed porcelain plate such as the back of a ceramic tile. They are moistened only with the smallest possible mist of solvent (a perfume spray bottle)and the plate left tilted to dry.
DISTILLATION: This is a method of purifying a substance in solution by means of relative boiling points. The boiling point (B.P.) of a substance is characteristic and usually expressed at or about sea level atmosphere pressure. As air pressure drops with altitude B.P. also drops. This is why Mountaineers carry tiny pressure cookers so that they can still cook their (mostly liquid) food! There are several kinds of distillation technique roughly grouped by the heat range employed. At a given heat of the flask every substance that boils at or below that B.P. will distill over and be condensed into the receiving vessel. Every substance with a higher B.P. will be left behind in the flask.
Destructive Distillation: This is a very high heat range industrial method of cracking crude petroleum into various liquid fuels. Products are naptha, gasoline, kerosene, diesel, etc. Dry wood is so distilled for turpentine, creosote, methyl alcohol, etc.
Direct Heat Distillation: This is the most common for crude distillation; an Erlenmeyer upon a lab. gauze heated by Bunsen or large alcohol lamp. Distillation flasks should contain a few pieces of broken glass (about sugar-cube size) to prevent the boiling vibration known as "bumping". The stopper carries a stick-form thermometer 9with its bulb within the flask neck to read vapour temperature. The L shaped glass tube exiting the stopper is connected to the central condensation tube of a water-cooled condenser by rubber tubing. This condensing tube is long for low B.P. (up to about 100 C.) and short for high B.P. (well over 100 C) The idea is to get proper condensation without the substance depositing in the condensation tube.
Fractional Distillation: This means the separation of several substances by more precise attention to the B.P. of the desired distillate 'fraction". To prevent "hot spots" in the Florence flask, it is often seated in a stainless steel bowl of water or dry sand; the bowl being heated by the burner. I have a 2 liter Florence sand-nested in the base of an electric 1100 watt deep-fat fryer. The thermostat switch helps to regulate the heat, but I wish there were a more precise thermostat probe through-the- stopper. As it stands, I must monitor and hand regulate to some extent. Also the little spark at the thermostat contacts could ignite volatile vapours unless bench ventilation fan is working. I DO have an electronic thermometer through the stopper into the vapour. it looks a bit like a lolli-pop with a digital readout in either 14 to 392 F. OR -10 to 200 C. within about 1 degree. There is an automatic minimum / maximum recorded in memory for batch records. This is item BA 080008 from WWW.marathonwatch.com
The "head" of a fractional still is more complicated. The flask neck is short and wide to accommodate a fractional column, often called a bubble tower. Their purpose is that the higher B.P. fractions do not pass over, but condense and drain back into the flask. The vapour thermometer is inserted into the top most tower stopper, below which a glass tube exits on a downward angle to the condenser. There are three main forms: Wurtz, Linnemann, and Hempel. Wurtz has several ascending simple glass bubbles, and condensation occurs on upper surfaces of the bubbles. Linnemann has small platinum screens between the bubbles and is more efficient but can be a bastard to clean. Hempel has a simple neck rising through the flask stopper, then widening to the appearance of a fat test tube with a condenser side stem. This column is packed with glass beads, and the top-most stopper carries the vapour thermometer. In my homemade version I use white glass beads about the size of pearls. The Hempel is simple and best suited to serious production of distillate. It is necessary to slack off on the heat from time to time to allow the bubbles or beads to drain themselves back into the flask.
Collecting Fractions: ideal condenser action should be a steady drip, drip, drip with very little escaping steam. If there is considerable steam lost at correct vapour temperature, then your condenser column is not long enough or the cooling water flow should be increased. Usually the first few drips from a still are impure as they pass over below true boiling point. Until you stabilize at the desired B.P. the "first runnings" are often collected in a small beaker and discarded. Now comes the real fraction passing over at the true constant B.P. When the flask level becomes low vapour temperature often begins to rise in spite of your care. These "last runnings" are collected in a separate beaker. Never allow a still to run dry as the flask may break! Note that the best fraction is considered to be the long middle run at correct substance B.P. vapour temperature in the still "head".
Distillation in Steam: This technique is best known for extracting 'essential oils' from herbs. The distillation flask is not directly heated; rather water is boiled in another flask and live steam is piped into the bottom of the distillation flask. The distillation flask contents are so heated by this steam-hose effect, that fractions arise within the waste steam to the condenser.
Vacuum Distillation: The above methods are considered Normal distillation, in that evaporation occurs at roughly normal atmosphere pressure. Vacuum distillation uses considerably reduced and regulated air pressure. This method is often used for exotic Organic substances not volatile at normal atmosphere, in partial vacuum these fractions may be distilled without damage to the molecule. I have only assisted with Vac rig, and so am not competent to talk about them.
THIS ENDS THIS TWO PART ARTICLE. Anarchism involves de-mystifying subjects as much as possible and empowering comrades with our experience. Since I have not seen such an article on lab set-up, I had to write one myself. May the sudden bright light always be at your back, may the better sort of Devils guide your feet.
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