Nearly all kind of chemical waste may be delivered to the "Materialverwaltung" (=Material Management) without any treatment. Only pressure gas cylinders which still contain gas may cause problems. Please feel free to discuss your specific problem with the "Materialverwaltung".
Very different problems
Organic acid halogenides
Since the reactivity may be very different, you will find here only some general hints. There are three possibilities:
- Dispose in a separate bottle. Advantage: Very easy, but it may be more expensive.
- Dispose as solvent waste. To avoid that all the waste will fly past your ears, you may add the acid halogenide only in very small portions. It is not needed that you spend hours or even days standing at the waste container, but only add a little bit from time to time, where it is best to do this with a proper filled waste container since in an empty waste container there is at the moment nothing wich will dectivate the acid halogenide and then you will have a desaster without any warning if the container is later on filled with other chemicals. This method is more effort but it will be cheaper. The safety is very enhanced if the mixture is stirred on adding the compound.
- Deactivation with water or alcohol. But even if you use "gratuitous" water the amount of waste increases and makes the disposing more expensive. A deactivation is only meaningful, if the mixture then may be disposed as organic solvent waste.
A deactivation is only meaningful if the quantity is so small that the resulting mixture may be flushed down the drain. Otherwise disposing the untreated compound in a separate bottle is more profitable.On hydrolysis in pure water an explosive reaction may occur with a perfidous time delay! It is better to use hydrochloric acid from the beginning as described below:
To a three necked flask equipped with dropping funnel and gas outlet pipe a little bit of hydrochloric acid is added. Then a little bit of phosphoroxychloride is added with stirring until the mixture is warmed up. Then ice and phosphoroxychloride is alternating added in a way the solution remains constantly slightly warmed and will not boil. The acidic gas is absorbed. Carefully ensure that the phosphoroxychloride will react instantaneously and never will form a separate layer! If you see a second layer, immediately stop adding the phosphoroxychloride and wait until the layer has disappeared. If the reaction is running propperly even larger amounts of the phosphoroxychloride may be deactivated quickly. If necessary you may additionally cool the flask in a bath.
Since the resulting mixture is very acidic, it should be neutralised. The salt solution may then be flushed down the drain.
A deactivation is only meaningful if the quantity is so small that the resulting mixture may be flushed down the drain. Otherwise disposing the untreated compound in a separate bottle is more profitable.
These kind of acid chlorides may be deactivated with diluted sodium hydroxide solution. If the reaction is too vigorous, add ice to the mixture. The resulting mixture may be flushed down the drain.
Do not blow it into the atmosphere!
In environment regulations the protection of territorial waters seemes to be much more important than the protection of the atmosphere. Nevertheless you may not blow acid gases like hydrogen chloride, hydrogen bromide or sulfur dioxide into the atmosphere.
As a rule all these gases are easily absorbed in sodium hydroxide solution. But there are two problems:
- A lot of heat may be developed during the reaction.
- The absorption is very vigorous and if there is not enough gas running to the absorption solution it is the absorption solution which will run back to the source of the gas. This may happen with the speed of a flash!
|If you use a gas washing bottle to absorb the gas usually a safety bottle (see left) is needed as a trap, if the absorption solution is sucked back. The problem is that if the absorption solution is sucked back it will move back and forth between the two bottles.|
You may avoid this problem if you do not immerse the gas inlet pipe into the absorption solution but let it end very close to the surface. Use your lab glass ware to fabricate your own gas washing bottle, where the height of the gas inlet pipe can be adjusted manually. See the pictures right hand to get an idea how to do this. The left apparatus has a free outlet and therefore has to be placed close to the fume hood flue. In both equipments the round bottom flask is the main part and contains the absorption liquid. The flask should be filled to the half of its volume, because in this case the surface of the solution is on its maximum. Adjust the size of the flask and the concentration of the absorption solution in a way that all of the gas can be absorbed. Since hydrogen chloride or hydrogen bromide dissolve very effectively in water approximately 80 % of the are removed. (Consider that the gas is heavier than the air and will therefore spread onto the water surface where it is absorbed.) Stirring is not necessary because the acid solution is also heavier than the pure water and will sink to the bottom of the flask. (You will see the streaks moving down to the bottom.)
If you are performing a reaction where cooling water is needed you may use this cooling water and the equipment shown in the picture to build up a simple gas washer. Consider that no water should flow through the cooling coils of the dimroth condenser. The cooling coils are only needed to distribute the water which is feed through the opening (A) of the adapter over a large surface. You may also use a Vigreux-column instead of the condensor. The opening (B) of the vacuum adapter is connected to the apparatus where the gas is formed. (A straight adapter does only look better and has no other advantages.)
The cooling water must not plug the outlet of the condensor, but has to rinse down without any pressure instead. Otherwise the water will move into your reaction apparatus! Plugging happens,
Place the end of the cooler over a sink. It is not needed to neutralize the diluted acid running out of the condensor because the lab waste water is neutralized automatically by the technical equipment of the institute.
Speeding up for disposing
Used fillings of a column chromatography (mostly silica gel) should be completely dry. Curiously after use the colums are often simply mounted upside down and then left standing alone to allow the content to fall out. But the wet material is sticky and it may need days and even weeks to get it out! But if air is suckd through the column the job is done within one hour! (Have a solvent trap in the line between column and pump!) During the process a cold zone is moving through the column. If it had reached the end of the column and had then disappeard the content is free flowing again.
Silica gel and alumina are disposed as "operating materials".
The canister for the solvents is sometimes not the best choice
Benzyl halogenides are very lachrymating agents. Additionally benzyl chloride is carcinogenic. Handle and dispose carefully!
You may dispose benzyl halogenides as solvents. With bigger volumes it may be better to dispose in a separate bottle because of the lachrymating effect and the reactivity. Benzyl halogenides may be purified by vacuum distillation. Benzyl bromide is less stable at room temperature but in a freezing compartment it becomes a solid and is savable. Since benzyl bromide is also not carcinogenic it is perfect to replace the benzyl chloride.
Distillation residue, contaminated glass ware
Rinse glass ware several times with acetone or ethanol. Each time allow the solvent to evaporate completely before you rinse again. Immerse soaking materials into alkaline alcohol solutions. Treat resin-like distillation residues also with alkaline alcohol solutions and reflux the mixture. The benzyl halogenides are deactivated there by a synthesis of ethers according to Williamson. The ethers are no more lachrymating and are disposed as solvents.
May easily be recycled.
Boron trifluoride etherate is a corrosive and toxic liquid which develops a lot of fog when exposed to air. When it comes in contact with water it vigorously decomposes to hydrofluoric acid and boric acid.
Substance of poor quality can be recycled by a simple vacuum distillation (Kp10 = 46 °C).
Small quantities may be deactivated by slow addition to sodiumhydrogencarbonate solution. Dispose bigger amounts witout any treatment in a separate bottle.
Please feel free to think about further usage.
Bottles which should be disposed have to be cleaned first to ensure that there is no more a hazardous potential. Use a suitable solvent, like water, water + soap or any other solvent if water does not work. With chemicals reacting vigorously with moisture (for example phosphorous pentoxide, phosphorous trichloride, chlorosulfonic acid) allow the opened bottle to stay in a fume hood until the hydrolyses with air humidity is completed. (This may need one day or even more.) Then rinse with water.
Remove all warning symbols/pictograms. It is best to remove the label completely, but if this does not work scratch the symbols/pictograms with a knife:
Dispose glass bottles into the glass waste container of the BSR (municipal cleaning service). You have to take the bottles yourself to the containers. (There is no room service!) Plastic bottles may be disposed into the yellow barrel. If you cannot find a yellow barrel the household waste container is also OK. If the containers are emptied by the cleaning staff please remove the cap of the bottles. Then it is easily to see, that the bottle contains no harzardous residues.
To leave bottles with a residue of 3 drops standing alone is no disposing!
If you have cleaned a lot of bottles at the same time for a furter usage you may run into trouble how to find the correct cap for each bottle.
A cap which cannot be srewed at least two full turns onto the bottle is not the correct cap!
A cap which is found aslope on the bottle is not the correct cap for that bottle!
A stiff cap is not the correct cap for the bottle!
If the bottle has a plastic lable first try to remove it. If this works and if there is no residue of sticky gum it should be profitable to clean the bottle for further usage. With a sticky gum you will need lots of solvent and much effort to remove it. Probably this is not profitable any more.
- If the bottle has a lable made of paper, immersed it into water for one hour. If it is then possible to remove the label with a knife or a razor blade (you may get a scraper with a razor blade at the "Materialverwaltung" (=Material Management)) it should be profitable to clean the bottle for further usage.
Plastic bottles are very suitable for disposing waste, because they are lightweight. But be careful that the waste does not affect the bottle.
If the bottle is not suitable any more the cap may still be useful. Prepare a stock of caps needed for all bottles found in your lab. You know that it will happen quite often that a cap breaks and in this situation it is pretty good to find a substitute in your stock.
Much too good to be disposed!
Bromine is rather expensive, very reactive and quite often needed. For these reasons you should avoid to dispose it. Please pass it to staff instead who can use the bromine. Purification by distillation is possible. Dispose in a separate bottle.
Small quantities and solutions
Bromine may be converted to bromide by a reducing agent. The resulting salt solution may be flushed down the drain. Often thiosulfate is recommended as a reducing agent but in this case sulfur precipitates quite often. Therefore it is better to use sulfite or hydrogen sulfite solutions which will give no precipitations. Since the reaction gives protons as a reaction product carefully prevent the mixture from becoming too acidic by adding sodium hydroxide solution. Otherwise unwanted sulfur dioxide gas may be developed.
Difficult to dispose
"Modern" safety regulations enforce that pressure gas cylinders which are only partially emptied cannot be returned to the supplier. This applies particularly for reactive gases.
Only buy volumes which you will use up!!
In a pressure gas cylinder chlorin gas is found as a liquid. This means that even small pressure gas cylinders contain a lot of chlorin gas. This means also that a full gas cylinder is much heavier in weight than an empty cylinder. Since the weight of the empty cylinder is stamped on its top you may determine the available amount of gas by simply weighing the cylinder. A suitable balance is found at the "Materialverwaltung" (=equipment counter).
Since the institute has to pay lending fees for the pressure gas cylinders please return all cylinders immediately if they are not needed any more!
Surplus chlorin gas in a reaction apparatus
Escaping clorine gas is absorbed as described in "acidic reaction gas". There the chlorine gas will disproportionate to chloride and hypochlorite. The hypochlorite should be transformed to the chloride by adding a suitable reducing agent (for example disulfite). Check with iodide if this reaction has been completed. With larger quantities of chlorine gas it is best to add the reducing agent already to the absorption solution. Regarding to ecological concerns a very nice method is to reduce the chlorine with hydrogen peroxide because then the salt concentration is very low. According to V.Wiskamp (personal information) the hydrogen peroxide has to be added slowly to the hypochlorite solution until the formation of gas ceases. More acurate is to check if 0.1 % methylorange dissolved in 2 % sulfuric acid is not decolorised by excess sulfite.
Deactivation needs a lot of resources
Chlorosulfonic acid develops a lot of fog when exposed to air and reacts very vigorously with water and even with ice explosively. During this reaction a lot of hydrogenchloride gas is formed. Old charges are often coloured brownish. Probably this is caused by corrosion of the bottle caps which often cannot resist for a longer period of time. (Have caps at hand for necessary replacement!) Since even traces of contaminations may give a considerable staining, a slightly colored liquid is probably not ruined!
Dispose pure chlorosulfonic acid without any treatment as a separate bottle. Take care to pack it securely. Especially take care to use a proper and tight closing cap!
If you are going to perform the following deactivation consider that a lot of sulfuric acid and sodium hydroxide or sodium carbonate are needed as auxilliary materials. Therefore a deactivation is only meaningful, if disposing as a pure compond is not possible or if it happens that the auxilary materials are also waste materials.
Put the chlorosulfonic acid into a three-necked flask with a dropping funnel and a reflux-cooler (equipped with a gas outlet pipe) and add carefully 60 - 70 % sulfonic acid through the dropping funnel. With a lower concentration of the sulfonic acid the reaction becomes more vigorous. Lots of hydrogen chloride gas is formed. Use the pipe to absorb this gas. If you like to cool the reaction flask in an ice bath consider that in case of a breakdown of the flask all of the acid will have contact with water! If this happens at the beginning of the reaction, this will end in a desaster!
If the reaction is going to subside you should lower the concentration of the acid. At the end add pure water. Leave the mixture standing alone. Blow a little air through the apparatus to remove the acid gas before you open it. The resulting mixture is neutralized with sodium hydroxide or sodium carbonat (Watch the foam!) and then flushed down the drain. Be aware that there will be a precipitation of sodium sulfate because this salt is not very soluble in water.
Do not treat pure compound. Try to precipitate from solutions.
- According to the regulations("Indirekteinleiterverordnung") waste water must not contain more than 0,2 mg/l. (Whereby the oxidation state is irrelevant.)
Do not treat pure componds but dispose in a separate bottle.
Concentration of Chromium Salts from diluted Solutions
Generally oxidation reactions of organic componds with chromium oxide yield lots of diluted aqueous chromium salt solutions. Disposing of these solutions is quite expensive because of the large quntities. Precipitating the chrome therefore can save money. But be careful: If the aqueous solution contains acetic acid it may happen, that a precipitation as described below is not complete!
- Reduce all chromium(VI)-componds to chromium(III)-compounds by adding disulfite. Calculate the necessary amount or use an excess.
- Adjust the pH to 7-11 to precipitate the chromium(III) as chromium(III) hydroxide. Be careful! Chromium(III) hydroxide is amphoteric! It will dissolve again if the solution becomes too basic. It is quite difficult to proper fix the pH since the mixture will not buffer the pH between 7 and 11 but it will do outside this range!
- Filter the green bulky precipitate and dispose it without further treatment (= without drying) in a separate bottle!
- Check the filtrate if all of the chromium has been removed. You may be sure that this holds true if the solution is colorless. Otherwise check if further chromium will precipitate on adding barium chloride. The solution must first be prepared to be neutral using an acetic acid / sodium acetate buffer.
- Immediately clean all used glassware, to avoid dust developed by dried material.
Chromosulfuric acid should not be in use any more. If there are still some old charges, dispose them as they are in the "Materialverwaltung" (=equipment counter). A deactivation as described above would need much effort, because the acid has to be highly diluted and lots of alkali would be needed. Additionally sodium sulfate would precipitate which is only poor soluble in water.
Never flush down the drain!
According to local regulations (Indirekteinleiterverordnung des Landes Berlin) waste water must not content more than 0,3 mg/l.
Dispose in a separate bottle.
The purpose of the following treatment is to reduce the quantity of the waste material and to save money.
Copper can be precipitated from aqueous solutions with hydroxide. Avoid an excess of the hydroxide since the copper will then dissolve again. Check with sulfide, if the precipitation is complete (black copper sulfide is formed). The precipitation may not work if there are organic compounds with hydroxigroups present which will give copper complexes (For example think of the tartrate used in Fehling solution). In these cases precipitate as sulfide in acidic solution. The precipitation is separated by filtering.
Dispose pure compounds in a separate bottle. With solutions it may be better to decompose or to precipitate the cyanide.
Just dispose as found in a separate bottle.
Maybe with solutions a treatment can save money.
a) Decomposing with hydrogen peroxide
The product of this reaction is ammonia/nitrogen and carbon dioxide. Therefore the resulting mixture may be simply flushed down the drain. But the reaction is only suitable for simple aqueous solutions. Since a lot of gas is formed during the reaction it is best to use a large beaker which is placed in a bowl, where the bowl is a safety measure if anything should bubble over. Adjust the pH to 10 - 11 and add excess hydrogen peroxide. The reaction is highly exothermic but needs an induction period. According to the literature the cyanide is oxidised to cyanate. But in own experiments forming of ammonia has been detected. When the developing of gas subsides change the pH to 8 - 9. Again a lot of gas is formed. Wait until no more gas and no more heat is developed. The Merck company suggests to check with a Merckoquant®Cyanide-teststick if all of the cyanide is decomposed. If you do not have this at hand at least you may check with a little crystal of iodide if there is an excess of oxidising agent. Verifying the cyanide as "Prussian Blue" generally will not work, since excessive peroxide will oxidise all iron(II) to iron(III), which will give poor soluble compounds.
b) Precipitation as "Prussian Blue"
This method is easy. It works with aqueous solutions and also in solutions containing organic solvents like ethylene glycol. Simply add a solution of iron(II)-sufate. Generally the iron(III) which is needed for the "Prussian Blue" is formed by autoxidation when the iron(II) has contact with air. Therefore the formed precipitate changes the color gradually from red to blue. You may accelerate this reaction by passing air through the solution. Depending om the Fe2+/Fe3+-ratio different products may be formed. The precipitate is filtered, washed with water and then disposed in a separate bottle. Subsequent oxidising according to a) does not work.
Dispose pure HMPA in a separate bottle.
With all other disposing methods be careful because of the hazardous potential!
Disposing into the solvent waste
Waste solvent cannisters remain unclosed during collecting the waste. Therefore it is a risk to fill in highly toxic compounds. You may avoid this problem, if you add the HMPA-waste at last before closing the cannister. Ensure, that the quantity is small enough that there will be no reaction with the other waste.
HMPA is completely decomposed on heating in conc. hydrochloric acid for 5 hours. Per Mol HMPA (179 g) 750 ml of the acid are needed. Install an gas outlet pipe into the fume hood's flue and boil the mixture vigorously. Take care to use enough of the acid because otherwise the deactivation may not be complete.
Easy to deactivate
The pure compound is disposed without treatment as a separate bottle.
With hydrogen peroxide hydrazine is instantaneously oxidised to nitrogen and water. The reaction will be violent if the mixture is not sufficiently diluted. Add the hydrogen peroxide until the evolution of gas subsides. More accurate is to check for the presence of free peroxide - for example with potassium iodide / acetic acid (See "Organikum"). When the reaction is finished the mixture may be flushed down the drain. A little excess of peroxide is no bigger problem than the oxidising suds of your washing machine at home. All equipment which has got contact with the hydrazine may also be decontaminated with diluted peroxide.
Be careful! Fire hazard!
Palladium-charcoal is self igniting in its reduced form! To oxidise it separate the catalyst from the reaction mixture and add hydrogen peroxide with stirring. The mixture will foam vigorously after a short induction period and will develop a lot of heat. (Use a high beaker and do not deactivate more than 10 g at the same time.)
Raney-Nickel catalyst is pyrophoric and thus has to be deactivated. Small quantities may be collected first covered with water. Do not deactivate more than 100 g at the same time.
To the catalyst 25 % hydrochloric acid is added in a beaker of sufficient size (2 l for 100 g of catalyst). On warming up the mixture the nickel will slowly dissolve. You may speed up the reaction very much by carefully adding 30 % hydrogen peroxide solution. Be very careful with the oxidising agent since the reaction will otherwise become too vigorous. Use the acid sparingly and add slowly more and more just to keep the reaction running and to avoid formation of gelatineous coagulum which may cover still reactive catalyst. For 100 g of the catalyst aproximately 400 ml of acid are required. The reaction is finished if there is no more black precipitation and a clear green solution is yielded.
Add a saturated hydrogencarbonate solution until there is no more foaming. Sodium carbonate is less suitable since the carbonate particles are enclosed by the gelatineous precipitation and will not react. The precipitation consists of basic nickel carbonate and is filtered off. Since the dust of nickel salts is carcinogenic put the still wet material in a separate bottle and clean all used equipment immediately.
The price for this deactivation is that the weight increases aproximately 8 times.
The filtrate may be flushed down the drain if it is clear and colorless. The mother liquor tends to form further precipitations and has then to be filtered another time. According to the local regulations (Indirekteinleiterverordnung des Landes Berlin) the concentration of nickel in the waste water must not exceed 0,2 mg/l.
Iodine may be disposed in a separate bottle. Since it is very expensive you should try to find a subsequent user instead.
Iodine with poor quality may be purified by sublimation. If this is too much effort if you are doing a research job, maybe this could be performed as an extra-experiment in a lab-course?
Small quantities typical for lab work may be reduced with sulfite and then flushed down the drain.
If you store it properly, you will have no need to dispose it.
- Lithiumaluminiumhydride which is partially decomposed and thus cannot be used in stoichiometric reactions any more may still be used to dry solvents. If you cannot find a subsequent user please feel free to make a donation to the OC-lab course.
- It is not true that active lithiumaluminiumhydride must be grey - it may also have a white color.
- Lithiumaluminiumhydride which seemes to be highly decomposed at the surface may be still very reactive in deeper layers. So do not become careless if at the beginning "nothing happens", if you are going to deactivate the compound.
- Pellets of lithiumaluminiumhydride are more resistent against decomposition and they are only slightly more expensive than the powder. A second advantage is that the pellets do not form any corrosive dust.
Proper storage helps that the lithiumaluminiumhydride remains active for a long time. Often the compound is delivered in a plastic bag and the bag is soldered in a can. If you open the can and then the bag and after removing the needed quantity you simply plug the bag back into the can then do not be astonished if it needs only days to get the lithiumaluminiumhydride decomposed. If it was you who opened can and bag then it is your job to transfer all of the material into a dry and wide necked vial. Empty the bag onto a sheet of weighing paper first and then transfer from the paper into the vial. Immerse bag and paper completely into water to ensure that there are no residues of active material. Then dispose into the household waste. Wipe the used work space with a moist cloth for the same reason.
Disposing of the pure compound
Dispose lithiumaluminiumhydrid in a separate bottle. Small quantities may also be deactivated. There are several methods of deactivation - all of them with advantages and disadvantages:
- Put very slowly into water
Advantage: Water cannot burn. The resulting mixture may be flushed down the drain.
Disadvantage: The reaction may be very vigorous and therefore has to be carried out very slowly.
- Put slowly into alcohol
Advantage: The reaction ist less vigorous than with water.
Disadvantage: Alcohol is highly flammable. You may run into trouble if you perform the deactivation too careless since the whole mixture may then ignite. Furthermore the final mixture must be disposed as toxic waste.
- Put slowly into ethyl acetate
Advantage: Very smooth Reaction
Disadvantage: It is difficult to detect the end of the reaction (no gas is developed), the mixture must be disposed as toxic waste.
Use water if possible!
Deactivation of reaction mixtures
Since in theses cases organic solvents are still present water is no more suitable, because on the vigorous reaction the mixture may ignite. Deactivate with ethyl acetate or better with alcohol (gas evolution to monitore the reaction). Take care that all of the compound is covered with solvent. Be very careful at the beginning - later on you may speed up the addition of the reagent. Do not be overhasty, but reserve sufficient time instead! The slower the reaction the lower the risk of an accident. If hydrogen gas is developed, draw it of in a pipe into the fume hood's flue.
When the reaction is died down leave the mixture standing alone over night. Next day add water - at the beginning very carefully and again leave the mixture standing alone. Precipitations are dissolved by adding hydrochloric acid.
Cleaning of equipment
Spatulas, flasks, filters, bags (where the compound has been delivered.) - all this is completely immersed in water (no air bubbles!) to decompose all adherent residues. Wipe used work areas or balances with a moist cellulose sheet.
- Never dispose untreated equipment into the material waste!
With solutions try to reduce the quantity to save money
To save weight and money a precipitation of the manganese compouns may be meaningful. On adding hydrogen peroxide to an aqueous solution of manganese compounds all of them are uniformly transformed to manganese dioxide. (Be careful! With permanganate the solution must be very diluted. Otherwise the rection may be explosively.)
The precipitated manganese dioxide is filtered off and dryed. Check the filtrate if the manganese is completely removed.
Always dispose mercury separately!
Never mix up mercury with other waste. If the mercury is already mixed with other material for example with sweepings, which has been swept from the area underneath the laboratory benches then dispose as "mercury containing sweepings" in a separate bottle. Dispose elementary mercury separately from compounds of mercury. It may happen that elementary mercury can be recycled (which is done by vacuum distillation).
Keep the weight of the waste low! If a mercury thermometer has been broken you may cut off all mercury-free glass with a glass cutter and dispose this a normal glass waste. Only the mercury-containg glass needs to be disposed as mercury-waste. But look carefully: If the mercury has been sprayed you may find lots of very small drops all over the glass surface.
Never spread any "helping" compounds onto spilled mercury!
Sulfur is without any effect and costs twice: First you have to buy the sulfur powder and second you have to pay also for the waste sulfur. Zinc powder is right the same! Iodized active carbon only helps for mercury vapors, with liquid mercury it does not do anything and the only effect is a calamitous daub.
If mercury is spilled over a wide area on the floor it is best to sweep it up. For a smaller area use a flat brush. With a plastic shovel at hand you may proceed to brush it onto the shovel. Use a funnel to decant the mercury into a separate bottle. Alternatively you may also use a sheet of zinc. The zinc sheet works only after having been etched with diluted hydrochlorid acid. Bring the etched sheet into contact with the mercury drops. The drops will "jump" onto the zinc. Look at the picture to get an impression how this works.
The arrow is pointing to a mercury drop which is just jumping onto the zinc. The absorbed drops may be shaken into a separate bottle. The zinc surface will become amalgamated and in this situation it is not oxidized as easily as pure zinc. But from time to time a reactivation with hydrochlorid acid is still needed. The zinc sheet may be used lots of times but on using it, it will slowly downsize.
Mercury has a poor reputation. The H-phrase 330: "Fatal if inhaled" is a part of the GHS-labelling. Nevertheless you will not perish at once, if mercury is spread anywhere. The reason is that mercury has only a very low vapor pressure at room temperature and moreover the vapor is much heavier than air and will fall to the floor. However, spilled mercury always must be removed completely, because continous breathing of mercury vapors even with low concentrations may cause diseases.
Deactivation is not necessary
Dispose in a separate bottle.
If you do not fear the satanic sibilance and if you act very carefully and slowly you may pour the oleum onto ice. It is a good idea to perform this reaction in a big round bottom flask which is filled with ice. Use a dropping funnel with pressure equalizing tube to add the oleum. This will prevent from smoke and splatters. If an open bottle should be used an erlenmeyer flask is best. A deactivation is only meaningful if the quantity is so small that the resulting mixture may be flushed down the drain.
Adjust Deactivation to the Reaktivity.
Organometallic compounds are deactivated similar to sodium or potassium. The reaction conditions have to be adjusted to the reactivity. The reaction is slower with higher and especially with tertiary alcohols. You may also slow down the speed by adding an inert solvent.
- Never cool the reaction mixture in an ice-bath if there could be a desastrous reaction if the flask breaks!
n-Butyllithium in Hexane
In contact with air n-butyllithium may ignite spontaneously! It depends on the concentration if this happens or not. Often a 15 % solution in hexane is used. This solution does not tend to ignite spontaneously. But be aware that the solvent may evaporate and the residue then may have a higher concentration of the n-buthyllithium.
n-Butyllithium slowly decomposes to lithium hydride which is also highly reactive and occurs as a white precipitate. But more often a preciptation is caused by lithium hydroxide which has been formed by a reaction of the n-Butyllithium with air moisture. With increasing precipitation the color of the solution changes from yellow to colourless. The supernatant liquid can still be used after the concentration has been checked by titration of a hydrolized aliqout.
n-Butyllithium may be disposed in a separate bottle. A deactivation as described below will yield products which will save money on disposing them.
Check every reaction in a tentative experiment before you allow a reaction of all of the compound.
Solutions with concentrations <= 2 molar may be decomposed by dropping them slowly into water. Very old solutions may even be poured into water. Higher concentrated solution may be diluted with hexane, but you should reflect, if this is meaningful since this will increase the amount of waste. With open bottles the solvent should not boil when it is mixed with water. The precipitation of lithium hydroxide may be dissolved with hydrochloric acid. At the same time the mixture is neutralized. The aqueous layer is flushed down the drain and the organic layer is disposed as solvent waste.
The reactivity is easy to handle
The same measures which ensure a safe transportation from the distributor to the consumer will also ensure a safe transport for disposing the compounds. Often this is done by adding water ("Phlegmatizing"). Dispose in a separate bottle. Deactivation cannot be performed by an all-purpose method and will enlarge the quantities to dipose.
If there are peroxides found in solvents there are several specific chemical methods:
- Iron(II)-sulfate (with diethylether)
- Copper(I)-chloride (with tetrahydrofuran)
- Tin(II)-chloride (with dioxane)
More ubiquitous is the adsorption on alumina. The capacity of the alumina denpends on the kind of solvent. Please see the instructions of the supplier of the alumina.
Hydrogen peroxide is very useful to deactivate other compounds. Therfore it should never be disposed.
If you have a pair of tweezers, maybe there is no need to dispose it.
Stored phosphorus pentoxide is going to be covered with polyphosphoric acid like a skin. If this "skin" is removed with a pair of tweezers you will again find a proper compond. "The-more-the-better"-user will often produce this kind of problem in desiccators, where a half pound of phosphorus pentoxid used as drying agent is soon without any effect, since it is separated from the scene by the "skin".
If you attempt to deactivate phosphorus pentoxide with water, you are penalised with lots of smoke, coughing, angry lab-neighbors and maybe also a broken glas container because phosphorus pentoxide reacts vigorously with water. It is better to leave the compond standing alone in contact with air and wait until it is hydrolysed by air moisture. If the powder has completely changed to a syrup, you may add riskless more water.
Batches which are completely decomposed are disposed in a separate bottle.
It is not "quite similar" to sodium but it is a complete new category instead!
Potassium is gradually covered with deposits of peroxo compounds (K2O2 und KO2) even when it is stored in a protective fluid. These deposits are very reactive and may burn or even explode on little pressure for example if lumps are grabbed with a gripper or cut with a knife. There have been fatal accidents on handling old potassium! The same may happen if you try to separate the pure metal from the oxide by melting the metal as described for sodium. Avoid the formation of the deposits:
- Only buy small quantities which are rapidly consumed.
- Check all new bottles and reject all of them where you will find potassion covered with peroxide deposits.
- Strictly exclude oxygen, for example by
- fusing in glass ampoules
- replenishing the protective fluid after removal of potassium lumps, so that the bottle remains free from air bubbles. Or flush with argon gas.
- Only use tightly closing caps.
On storing potassium the hazard will grow more and more. Deactivation with t-Butanol as described below will then not be without risk. Especially yellow or red deposits are very dangerous. The problem is that there is no disposal company which will take charge of the potassium. The only way out will be to burn the potassium - best in the closed bottle and watching the combustion gas and the flying splinters.
Potassium is much more reactive than sodium and will react with ethanol or isopropanol too vigorously. Use 2-Methyl-2-propanol (tert-Butylalcohol) instead! Since the metal is covered with the oxide deposits the reaction may only start after a long induction period. Potassium tends to form clusters which may persist for a long period of time. If the reaction dies down you may carefully add isopropanol or ethanol.
- Since even on most careful treatment spontaneous ignition may occur it is best to perform the reaction under an inert gas atmosphere. Never use large mouth containers like a beaker.
- Do not cool the reaction container in an ice bath. If the container breaks - and this might happen because of the strong heat - the metal will get into contact with water - and you do not like what will happen then...
- Unfortunately a big excess of the solvent is needed to deactivate the potassium. If the concentration of the potassium alcolate, formed by the reaction, is too high the mixture will become viscous and then cannot cool the metal any more. In the worst case a potassium cluster may heat up until it is glowing and then ignite the whole mixture. This is a second reason not to use an ice bath since the cold solution will become viscous more easily. Keep the mixture thin fluid! It is self-explanatory that the potassium has to be transfered into excessive alcohol. Never drop the alcohol on excessive potassium! If there are residues in a container which cannot be removed, cover with an inert solvent to ensure sufficient cooling and then drop the alcohol to that mixture.
- Dispose the potassium without rushing! Ensure that there is enough time for the job! The weaker the reaction the more safe is it.
Leave the mixture standing alone over night. Next day add more ethanol and at the end add carefully water. All the time watch, if there is a reaction! Leave the mixture standing alone another night.
Even if you do all this very carefully the reaction still remains hazardous. Be prepared to fight a fire all the time (safety trough, extinguishing agents, exclusion of all flammable compounds in the immediate vicinity). Only dispose the mixture to the organic waste solvents, if it is absolutely free of any metal residues. Ensure this by filtrating the mixture. The filtrate must be a completely clear solution.
More hints see disposing of sodium. Especially take care to effectively draw off the developed hydrogen gas, and carfully watch all the used equipment, if there are residues of the potassium. Only regard equipment as metal free, if it has been immersed completely and air-bubble-free in water.
There are people who say that because of the hazardous potential it is more save to burn the potassium in open air. Concerning the work safety this seems to be argueable in this case, but doing so you should be experienced how to perform the burning safely. (Sandbox, splinter shield, for example using a tin bucket etc.) Furthermore you should have an idea how to dispose the residues.
Do not hord!
Pressure gas cylinders cause rental costs. The institute did make a contract with the provider company about a quota. If there are more cylinders than that quota, the surplus cylinders are producing exorbitant costs!
- Only have that minimum of pressure gas cylinders in your lab which is needed for your work!
- Return empty cylinders immediately to the "Materialverwaltung" (=Material Management)!
- Do not lose the overview about ordered and used pressure gas cylinders. (= Do not leave and forget cylinders anywhere.)
Pressure gas cylinders may only be used for a limited period of time. This deadline is stamped on the cylinder (see picture). If the time is up and the cylinder still contains pressure gas a special disposing is needed which may cost 20 to 700 €, depending on the kind of gas, the volume of the cylinder and the residual pressure. You may only avoid these costs, if the cylinder is completely emptied and therefore can be disposed as metal waste. The complete emptying has to be ensured by opening it up by drilling or by removing the main valve. (Drilling or removing of the valve is of course not your job but is done by a technician of the institute.)
Make it cheaper
Salts of heavy metals which should be disposed often are found as an aqeous solution. If the solution is disposed without any treatment this will be quite expensive because then a lot of water has to be disposed as toxic waste. So it is a good idea to think about to separate the metal salts as a precipitation. The precipitation must be completely - with complex mixtures may be this cannot be ensured. According to local regulations (Indirekteinleiterverordnung des Landes Berlin) there are threshold values for the following metals in the waste water:
Waste heavy metal salts may be collected together in the same bottle. An exception is mercury which always has to be disposed separately.
Only deactivate with surplus ethanol! May be recycled!
The pure compound can be disposed in a separate bottle. Ensure a safe packaging. If the metal is covered with deposits there is no need to dispose it but the metal - if performed properly - can be easily separated from the deposits by melting it. This even may be performed in a student's lab course.
On the other hand sodium can be deactivated with alcohols, but you will need lots of the alcohol which at the end is diluted with water. This means that a big volume of solvent mixture has to be disposed at the end.
b) Deactivation of pure sodium
Put the sodium slowly into alcohol.
- You may slow down the reaction speed if you use iso-propanol first and only later on proceed with ethanol.
- All the time make sure that there is enough surplus alcohol to ensure that the solution remains thin fluid. If there is not enough of the alcohol sodium alcoholate will precipitate which makes the solution viscous. Then the metal is not cooled any more and it will worm up until it is glowing. If the mixture becomes viscous, add more alcohol. If more than half a teaspoon of sodium has to be deactivated stirr the mixture.
- To avoid thickening of the mixture it is convenient if it warms a little up. Prevent from boiling. It is careless to cool in an ice bath since there will be a desastrous reaction if the flask breaks and the metal comes into contact with water. Wait until the temperature lowers alone instead.
- Pass the hydrogen developed into the fume hoods flue. Place low quantities which are deactivated in a beaker direct to the fume hoods flue.
- If the deactivation is performed in a beaker place it in a plastic bowl. If the beaker breaks or if the mixture boils the bowl will pick up the mixture. With an open beaker allways be aware that the mixture could ignite, because of the oxygen in the atmosphere. Therefore only deactivate small quantities in a beaker. If the mixture ignites the problem often is enlarged because the beaker is tipped over because of a startle response. You may avoid this problem if the beaker is clamped.
- Monitor the reaction until it is died down. Reserve enough time for this job!!
Final treatment of the mixture see d)
c) Destillation residue if a solvent has been dried over sodium
The sodium should be covered completely with the solvent. Add alcohol to the mixture - at the beginning very slowly and at the end more quantities. Again the mixture has to remain thin fluid. If necessary add more inert solvent (hexane, petrolether, toluene). See hints given in b).
Final treatment of the mixture see d)
d) Ensure that all of the sodium is deactivated
- Destroy all remaining sodium clusters (for example with a spatula). Check the walls of the reaction bottle, if there are residues of the metal. Stirr thoroughly.
- If the mixture is cloudy you may not expect that the reaction is finished if you do not see any evolution of gas. It is better to filter these mixtures to detect all remaining solid material. If there is still sodium present, treat with more alcohol as described in b).
- If the reaction has died down leave the mixture standing alone for several hours - better over night.
- Dilute the mixture with water - at the beginning slowly. All the time watch for developing of gas. When all the reactions are died down stirr thoroughly and again leave the mixture standing alone for several hours.
- Filter the mixture. The filtrate is a very useful reagent to deactivate other chemicals like benzyl halogenides or organic acid halogenides. Therefore only dispose as solvent waste, if you do not need the mixture for that purpose.
- Depending on what is found on the filter treat it either with water or with ethanol.
- All used equipment is only free of sodium if it has been immersed completely into water and you do not see any reaction. All solutions are only sodium free if they have been filtered.
If there are clumps, the compound is still OK.
Sodium nitrite is hygroscopic an may therefore form pretty hard clumps.
But these Clumps can easily be pounded in a mortar. The useful compound is each time separated by sieving. To get 1 kg pourable again 15 minutes are needed, wherat the sieving is the key for success. Use a simple halfround household wire sieve. Moisture may be removed on heating in vacuum at 170 °C.
Dispose in a separate bottle.