General Chemistry

Here is where it all starts. Proper laboratory technique and safety information is provided. Also provided are a few inorganic synthesis and some basic explanations of chemistry. Maybe someday you'll be the next great chemist to go down in history.


Laboratory Safety


Lab Techniques:

Cooling and Cooling Baths

Drying and Dessication


Filtration (Standard and Vacuum)

Fractional Distilation

Fractional Crystalization



Simple Distilation



Vacuum Distilation

Inorganic Syntheses:

Chloric Acid
Hydrobromic Acid
Hydrochloric Acid
Hydroiodic Acid
Nitric Acid
Perchloric Acid
Carbon Dioxide
Hydrogen Chloride
Hydrogen Sulfide
Nitrogen Dioxide
Nitrogen Monoxide
Nitrous Oxide
Sulfur Dioxide
Copper Sulfate
Lead Nitrate
Silver Nitrate
Sodium Hydrosulfide
Sulfur Dichloride
Tin (II) Chloride



Chloric Acid <30%

Formula: HClO3(aq)
Boiling Point: Decomposes Melting Point: ??
Density: ~1.0g/ml (30%)


Chloric acid can be prepared simply by reacting barium chlorate with sulfuric acid to form the chloric acid and barium sulfate. Barium sulfate is insoluble in cold water and therefor will fall to the bottom of the reaction vessel. Chloric acid will decompose if it is in solutions greater than 30%. To prepare:

Mix 50mls of concentrated sulfuric acid (96% or greater) with 275mls of distilled water. Place this into an ice bath and bring it close to 0C after it is completely stirred. Weigh out 152grams of barium chlorate. Add this to the diluted sulfuric acid in small ammounts with stirring. Monitor your temp and don't let it get above 15C (It decomposes if it gets too warm). When all of it is added, stir for 5-10 more minutes and then let the barium sulfate settle to the bottom. Cool an all glass reagent bottle in the fridge. After an hour or so, take the chloric acid out of the ice bath and decant the fluid off the barium sulfate into the cooled reagent bottle. Store this in the frige until its ready for use.


Hydrobromic Acid, 48%

Formula: HBr(aq)
Boiling Point: 126C (48%) Melting Point: -86C (48%)
Density: 1.49g/ml (48%)


Hydrobromic can not be found OTC and is a watched chemical so it would be hard to buy it from a chem supplier also. It is good for making alkyl bromides (such as methyl bromide) and bromide salts. It is produced by reacting sodium or potassium bromide with sulfuric acid.

Into a 1000ml flask, pour a solution of 190grams of sodium bromide and 200ml of water. Place a thermometer in this flask to monitor the temperature Place this flask in an ice bath to chill the solution. Prepare another solution using 90mls of concentrated sulfuric acid and 90mls of water. Chill this in the ice bath as well. When the diluted sulfuric acid is cold, add it carefuly to the flask. Do not allow the temperature to go above 75C or it will oxidise the bromine out of the sodium bromide. Once this is all added, warm the mixture up to room temp. Set the flask up for simple distilation with a thermometer. Make sure the thermometer is properly calibrated. Start distiling the mixture and collect the fraction that comes over at 125-126C. This is ~48% Hydrobromic acid.


Hydrochloric Acid

Formula: HCl(aq)
Boiling Point: 109C(20.2%) Melting Point: -74C(31%)
Density: 1.15g/ml (31%)


Hydrochloric acid is commonly available as "Muriatic acid" usually in concentrations of 31.45% HCl. It is not necesary to prepare this as it is so widely available but you can if you want to. Hydorchloric acid is prepared by bubbling hydrogen chloride gas into water. Read how to prepare hydrogen chloride on this page. Upon heating, concentrations above 21% will loose HCl until about 20.2% concentration where it forms a constant boiling azeotrope


Hydroiodic Acid, 57%

Formula: HI(aq)
Boiling Point: 127C (57%) Melting Point: -18C (57%)
Density: 1.7g/ml (57%)


Hydroiodic acid is a colorless to yellow and sometimes brown due to decomposition. It is another Hydro-halogen acid that is watched by the DEA. It is made by a single-displacement reaction using hydrogen sulfide gas and pure iodine.

Crush up 125grams of iodine (use gloves) and pour this into a 500ml flask. Add 200mls of water to this and swirl. Very little iodine will dissolve, but its good to make it contact all of the iodine. Affix a two hole stopper to this, one hole with a tube extending to the bottom minus 0.5cm. That means, push the tube down to the bottom of the flask and lift it up about 5mm. In the other hole, place a piece of glass tube so that it just barely extends below the rubber stopper. It helps to employ magnetic stirring in this flask but its not neccesary. Bubble hydrogen sulfide gas into this using the long glass tube. 1 mole of hydrogen sulfide gas should be sufficient to complete the reaction. You can tell when the reaction is complete when the water in the flask is clear but has sulfur suspended in it (and when there are no more iodine crystals on the bottom of the flask).

To obtain the 57%: remove the stopper from the flask and insert a thermometer. Under a fume hood, heat the flask to remove any hydrogen sulfide gas. Do not let the temperature go above 120C or you will loose some of your product. You can test for hydrogen sulfide by pouring 1ml of this solution into 10ml of a 10% copper nitrate solution. Once all the hydrogen sulfide gas is gone, set the flask up for distillation. Distil and collect the fraction between 125C and 127C. This is of sufficient purity for most reactions. Store in an amber bottle to help slow down decomposition.

Nitric Acid, >90%

Formula: HNO3(aq)
Boiling Point: 85C (90%) Melting Point: -50C (90%)
Density: 1.5g/ml (90%)


Nitric acid has infinite uses in the chemistry world. It can be used for making metal nitrates, it can be used for oxidations even at 70% concentrations, and it can be used to make explosives like nitroglycerin. It is made by distilling a mixture of potassium nitrate and sulfuric acid. I found that potassium nitrate gives best results for this but there is nothing wrong with using other nitrates for this.

To a 500ml flask, add 200grams of potassium nitrate. Measure out 100mls of sulfuric acid and pour it in. Set the flask up for simple distilation and place in an oil bath. Heat the oil bath up to 150C and hold it there until distilation is finished. This will maximum ammount of nitric acid, but will also increase decomposition of the nitric acid (this is why there is a yellow color). This process will make at least 75mls of concentrated nitric acid. This concentrated nitric acid can be mixed with half its volume in sulfuric acid and redistilled using a water bath to obtain pure nitric acid (at least 98%). 100% white fuming is only possible with reduced pressure, sadly. It would be wise to perform a titration on a sample of this and figure out its concentration, then dilute it accordingly to 70% concentration since most procedures only need 70%.

Perchloric Acid, 70%

Formula: HClO4(aq)
Boiling Point: 203C (70%) Melting Point: -18C (70%)
Density: 1.664g/ml (70%)


Perchloric acid is used for making Metal perchlorates and is another strong acid like sulfuric and nitric acid. It is made by reacting an alkali perchlorate with sulfuric acid, then distilling it off. Perchloric acid should only be handled in concentrations of 72% and below. 100% perchloric acid can explode. At ~70%, perchloric acid forms an azeotrope which is what we are aiming for in this reaction so that you can distil it safely.

To a 1000ml flask, add 250grams of potassium perchlorate. In another vessel, prepare a solution of 100mls of water and 50mls of concentrated sulfuric acid (Be careful of the temperature). Once the diluted sulfuric acid solution cools down, add it to the potassium perchlorate. Set the flask up for simple distilation. Place it in an oil bath and begin heating. At first water will distil over. Collect that fraction distilling between 201-210C which will be mostly ~70%. If necesary, redistil collecting the fraction between 202-204C. Yeilds should be around 150mls max of perchloric acid.




Acetylene gas is a colorless, odorless gas. Some people may argue against that since acetylene from an acetylene torch smells like garlic. This is not from the acetylene, it is from carbides that have built up inside the torch. Pure acetylene has no smell. It is generaged by the decomposition of calcium carbide using water.

CaC2 + H2O ----> C2H2 + CaO

The excess water will react with the CaO forming Ca(OH)2

To generate acetylene, add about 5 grams to a sidearm flask. Set up an adition funnel with this and fill it with distilled water. Just pour the water in and acetylene will be generated. You don't want to waste calcium carbide because you wont be able to remove the impurities from this reaction. Just use small ammounts and add it as you need to.


Ammonia gas is a colorless gas that is lighter than air and has a strong characteristic ammonia like smell (whooda thunk it). It can be bubbled into water to make an aqueous ammonia solution or can be dried and used for other reactions. There are two main ways you can get ammonia: a double decomp reaction of ammonium nitrate and sodium hydroxide or releasing it from storebought concentrations of ammonia water.

1) Ammonium Nitrate and Sodium Hydroxide:

NH4NO3(s) + NaOH(s) ----> NH3(g) + NaNO3(aq) + H2O(l)

To a 500ml sidearm flask, add 80grams of ammonium nitrate. Quickly measure out 40 grams of sodium hydroxide and pour it in. A reaction will usually start once this happens so stopper the flask as soon as the sodium hydroxide is added. In 1-2 minutes, open the flask and add one dropper full of water (~1ml) and quickly close it again. This will provide rougly 1 mole of ammonia gas.

To produce 1 liter of a 30% ammonia solution using this method, use 945grams of ammonium nitrate and 475grams of sodium hydroxide. Into a 1000ml flask, poure exactly 1000ml of water and mark a line on the glass where the water reaches. Pour the water out and add 670mls of distilled water. Bubble the ammonia gas through until the water inside the flask reaches the 1000ml mark. You now have 1L of ~30% ammonia soluion. This method is not efficient as you need almost a kilogram of ammonium nitrate. It would be cheaper just to buy the concentrated ammonia water from a chemical supplier.

2) Isolating from storebought ammonia water:

The typical concentration of ammonia water you can buy at the store is between 7 and 10%. All you have to do is fill a flask with a volume of this and heat it. The ammonia will be driven off as a gas. To prepare a 1L solution of 30% ammonia, Fill a 1000ml flask, marked at 1000mls, with 670mls of distilled water and bubble dry ammonia gas into this until the water reaches the 1000ml line. It isn't important if the gas is dry, but you will get more acurate results if it is. When ammonia is made, there is usually always a significant ammount of water present which will dissolve into the solution and give you a false reading.

**To dry ammonia gas, pass it through a drying column containing an anhydrous alkali hydroxide (such as NaOH). Do not use CaCl2 as it will form complexes and don't use H2SO4 because it will form ammonium sulfate.


Chlorine is a yellow-green gas with a pungent odor, similar to bleach. It is used for many reactions such as chlorination of organic compounds. It is produced by the oxidation of hydrochloric acid with manganese dioxide. Other oxidisers can be used but manganese dioxide wastes the least ammount of chlorine (chlorine gets wasted by forming chloride compounds with the oxidiser).

MnO2 + 4HCl ----> Cl2 + MnCl2 + 2H2O

Fill a sidearm flask with 87grams of manganese dioxide and set it up with an addition funnel. To the addition funnel add 410mls of Muriatic acid (31.45% HCl). Add the hydrochloric acid in 4 portions, each portion after the chlorine flow starts slowing down. It would also help to put the flask on low heat and stir it for maximum chlorine production. This will produce roughly 1 mole of diatomic chlorine gas.

**There is another process out there that uses Trichloroisocyanuric Acid or TCCA. TCCA + Hydrochloric acid is much more efficient than any other methods as no chlorine is wasted.

C3Cl3N3O3 + 3HCl -----> 3Cl2 + C3H3N3O3

Add 230grams of TCCA to a sidearm flask and set it up with an addition funnel. To the addition funnel add 305mls of Muriatic acid (31.45% HCl). Add this in 3 portions, each portion after the ammount of chlorine being produced reduces. The reaction is more efficient when heat and stirring is applied. This method can produce rougly 3 moles of diatomic chlorine gas. TCCA can be purchased at a pool and spa store as a chlorinating agent for pool water. It will usually also contain copper sulfate for various reasons.

To dry chlorine gas, pass it through a drying tube containing prilled calcium chloride.

Carbon Dioxide

Carbon dioxide is a colorless gas which has many uses in the industrial world. It is used for extracting the caffeine out of coffee beans, as a propellant for paintball guns and pellet guns, and as a fireextinguishing medium. It is made by neutralizing hydrochloric acid with calcium carbonate. In the chemistry world it is used for lab demonstrations and for providing an inert atmosphere in some reactions.

Into a sidearm flask, place 125grams of calcium carbonate. Fit the flask with an addition funnel and fill this with 250mls of ~30% HCl. On the addition funnel, place a peice of tubing that extends below the surface of the calcium carbonateOn the sidearm, place a latex tubing. In a calcium chloride tube, pour a 1:3 mixture of calcium chloride and sodium carbonate. This will dry the gas and also neutralize any hydrogen chloride that comes over with the carbon dioxide. To drive off any remaining CO2 in the reaction flask, heat it to about 85C. This process generates a little over 1 mole of carbon dioxide gas.


Hydrogen is the most abundant element in the universe (not the earth though). It is a colorless, highly flammable gas. Hydrogen is completely non-toxic infact it is less toxic than oxygen but it can displace the oxygen in your lungs and you will suffocate if you breath pure hydrogen. Though it is non-toxic, if inhaled it can explode in your lungs if provided an ignition source. Hydrogen is generated by the reaction of hydrochloric acid on zinc metal.

To a 500ml sidearm flask, add 70grams of zinc metal. Fit this flask with an addition funnel and fill with 250mls of ~30% HCl. To dry the gas, first bubble it through water to remove any hydrogen chloride present, then through a calcium chloride tube containing calcium chloride. This process will generate rougly 1 mole of hydrogen.

Hydrogen Chloride

Hydrogen chloride is a colorless gas with a smell of hydrochloric acid. It is produced by the oxidation of sodium chloride with sulfuric acid.

To a side-arm flask, add 60grams of sodium chloride. Fit this with an addition funnel and fill with 60mls of concentrated, room temperature sulfuric acid. To dry the hydrogen chloride, pass it through calcium chloride. Heat the flask on low to generate more hydrogen chloride gas. This method should generate 1 mole of hydrogen chloride gas

Hydrogen Sulfide

Hydrogen sulfide is a colorless, deadly gas with the smell commonly described as sulfur (though pure sulfur has no smell). This is what is responsible for that sulfur smell when you turn on the faucet sometimes. The toxicity of hydrogen sulfide ranks up there with hydrogen cyanide, which is what is used in the gas chamber. Please be very careful with this gas and only work under a fume hood or outdoors or better yet, don't work with it. When you breath it in for the first time, it will dull your sense of smell (only short term, its not permanent) so therefor you wont be able to smell it anymore and it will seem as though it is not present.

Method 1 - Mineral acid and metal sulfides:

First, prepare a dilute solution of hydrochloric acid using 1 part muriatic acid and 1 part distilled water. This will be rougly a 15% solution. Set up a 500ml side-arm flask with 45grams of powdered iron sulfide and fit with an addition funnel. To the addition funnel add 250mls of this dilute hydrochloric acid solution. Bubble the gas through a flask of water before it reaches its reaction vessel to remove any hydrogen chloride gas that came with it. These amounts will theoretically produce 1/2mol of hydrogen sulfide.

Due to the costs of iron sulfide, some cheaper solutions may be utilized. For sodium sulfide, substitute 40g in place of the 45g. For potassium sulfide, substitute 55g. For Calcium sulfide, substitute 37g.

Method 2 - Paraffin wax and Sulfur:

Another method of producing hydrogen sulfide exists. However, due to it's great advantages, it also has some disadvantages. It involves oxidising paraffin wax with elemental sulfur. Unlike the metal sulfides in the above procedure, both chemicals for this can be bought at a super market. The disadvantage to this is the leftover carbon will ruin the reaction vessel. So choose a vessel you want to only use for doing this reaction.

Combine 20g paraffin wax shavings/chunks (they just have to fit inside the flask) with 40g elemental sulfur. Now, purge the flask with nitrogen gas. This is because the oxygen in the flask will react with the hydrogen sulfide (at these temperatures), producing sulfur dioxide which will usually mess with the reactions you need H2S for. An even better option would be a gas like helium or argon, but not everyone has those. Now, simply heat this up quite hot. First the sulfur and paraffin will melt (and separate into two layers) then it will gradually turn darker until eventually bubbles will be evolved. Be smart about the design of your gas system, as it is not uncommon for some sulfur to distill over and clog your glass tubing. The amounts above will theoretically produce 1mol of hydrogen sulfide.


Nitrogen is another colorless gas and is the most abundant gas in our atmosphere, being 78% of the air. It is used as an inert atmosphere for some reactions. It is made by oxidising ammonia with calcium hypochlorite

4NH3(aq) + 3Ca(OCl)2(s) ---> 2N2(g) + 3CaCl2(s) + 6H2O(l)

To a 1000ml flask, add 75grams of calcium hypochlorite. Fit this with an addition funnel and fill it with 350mls of janitorial strength ammonia (10% solution). Also fit a gas adapter to the flask or a rubber stopper with a peice of glass tubing in it. Bubble the gas into water first to remove any ammonia, then dry it with calcium chloride if neccesary.

Nitrogen Dioxide

Nitrogen dioxide is a poisonous, red/brown gas. It has very little use in the home-chemistry world so there is no real point to generate it but it is generated by the action of concentrated nitric acid on copper.

4HNO3 + Cu ----> Cu(NO3)2 + 2NO2 + 2H2O

To a 500ml sidearm flask, add 32 grams of copper filings. Fit an addition funnel to this flask and charge it with 130mls of 70% nitric acid. Have a tube coming down from the addition funnel to the copper so that the nitric acid wont splatter when its dripped onto the copper fillings. The NO2 coming out is of reasonable purity and would be hard to purify any further since it reacts with water and most dessicants.

Nitrogen Monoxide

Nitrogen monoxide is another colorless gas but no less deadly than nitrogen dioxide. On contact with air, nitrogen monoxide oxidises to nitrogen dioxide. It is produced by the action of dilute nitric acid (5%) on copper filings.

8HNO3 + 3Cu ----> 3Cu(NO3)2 + 2NO + 4H2O

To a 150ml flask, add 2 grams of copper filings. Set this up with a 150ml addition funnel and a tube going out of the flask for the nitrogen monoxide. Its a good idea to completely connect the apparatus to whatever other apparatus needs the nitrogen monoxide. On the addition funnel, make a tube that extends down to the bottom of the flask (but not touching). Make sure this is air-right, then charge it with pure, dry carbon dioxide. Enough to make sure that it is oxygen free. Now, fill the addition funnel with 110mls of dilute (5%) nitric acid. You can pretty much add all this at once to the copper since the reaction is fairly slow. This will produce roughly 0.02 moles of nitrogen monoxide (1 mole of nitrogen monoxide would take 10 liters of 5% nitric acid).

Nitrous oxide

Nitrous oxide is a colorless gas with a sweetish smell. It is known as NOS(which is a brand name) in the automotive racing world and is also an anesthetic used by dentists. It is produced by the thermal decomposition of ammonium nitrate.

NH4NO3 --215C--> N2O + 2H2O

Fill a 250ml sidearm flask with 85grams of ammonium nitrate. In the stopper to the flask, insert a thermometer that can go up to at least 250C. Extend the thermometer below the surface of the ammonium nitrate. Have this set up to first bubble it into a 1L flask containing 500ml of water then into a calcium chloride drying tube containing calcium chloride. Begin heating the flask. First it will melt around 170C then at about 210, it should start decomposing. Keep raising the temperature up to about 215 and hold it there. Temp control is important otherwise you'll burn stuff.


Oxygen is the most abundant element on earth. It has many uses in the chemistry world but most of them need oxygen based compounds as opposed to the gas. Oxygen is produced by the catalytic decomposition of hydrogen peroxide.

First, dilute 110mls of 30% hydrogen peroxide with an equal ammount of water (or 120mls of 27% hydrogen peroxide with an equal ammount of water). Next place 50grams of manganese dioxide (don't worry, you'll get it back) in a 500ml sidearm flask. Set the flask up with an addition funnel and fill the addtion funnel wither either your 220mls of diluted 30% or 240mls of diluted 27% hydrogen peroxide. It is a good idea, though not neccesary to bubble the oxygen into some water first to remove any hydrogen peroxide and then you can dry it using calcium chloride.

Sulfur Dioxide

Sulfur dioxide is a colorless gas with the pungent "burning sulfur" smell. To most people, it is useless but there are some specific syntheses that require sulfur dioxide gas in the preparation. It is generated by the action of hydrochloric acid on sodium bisulfite (not bisulfate).

HCl + NaHSO3 ----> SO2 + NaCl + H2O

To a sidearm flask (250ml minimum), place 100grams of sodium bisulfite. Attach an addition funnel to this and add 100ml of ~31% hydrochloric acid. Begin the addition and heat the flask gently if neccesary. The gas can be dried using calcium chloride. This procedure will generate 1 mole of sulfur dioxide gas, but of course some will be dissolved in the water thats formed as a by-product and some will still remain in the apparatus after it is done generating gas.



Lead (II) Nitrate

Lead nitrate is a chemical that is used every now and then. Not enough for it to be bought in large ammounts so I will describe how to make it. It's manufacture is fairly simple. Its formed by reacting lead metal or Lead II Oxide (Litharge) with nitric acid.

Pb + 4HNO3 ----> Pb(NO3)2 + 2NO2 + 2H2O

PbO + 2HNO3 ----> Pb(NO3)2 + H2O

If you are starting from lead metal; Place 20g of lead pieces in a 500ml flask or similar device. In a graduated cylinder, measure out 30ml of distilled water. Add to this 30ml of 70% nitric acid. Add this to the lead in the 500ml flask. Swirl it every 5 minutes as lead nitrate will build up on the lead metal. After a while the reaction will slow down. Place this flask in a warm water bath and heat it to 70C. If it looks like no more lead is dissolving, add another 5ml of nitric acid. When all, or most of the lead has dissolved (reacted), add 300ml of water. Bring it up to boiling then filter it. When you filter it, all of the lead nitrate should be dissolved. Boil this solution down to ~100ml and pour in a 200ml evaporating dish. Evaporate to solid.

If you are starting from lead monoxide; Place 22g of lead monoxide in a 250ml flask or similar device. In a graduated cylinder, measure out 30ml of distilled water. Add to this 20ml of 70% nitric acid. Add this solution to the lead monoxide in the 250ml flask. Swirl it every once in a while until there is little or no black left (lead monoxide). Add 300ml of water and bring it to a boil. Filter while hot and then boil the solution down to ~100ml. Pour this into a 200ml evaporating dish and evaporate to solid.

Silver Nitrate

Silver nitrate is almost always cheaper to make than to buy. It is used for various reactions involving explosives (such as silver acetylide, and fulminating silver) and is useful for many other things, such as making a water sensitive flash powder with magnesium. It is very easy to make and only requires silver metal and nitric acid (of any concentration).

Ag + 2HNO3 ----> AgNO3 + NO2 + H2O

Place 10g of small silver peices, or small mossy silver peices into a test tube. To this, add 12ml of nitric acid at 70% conc. (1.51g/cm3), followed by 10ml of distilled water. Depending upon the temperature of which the reactants have been stored, heating may be required. After all the silver has been dissolved, you should be left with a green solution. Add this to 50ml of warm distilled water in a 100ml beaker or similar device. Begin boiling it down until only a saturated solution of silver nitrate remains. Add this to an evaporating dish and continue to heat. Eventually, you will be left with pure silver nitrate. Theoretical yeild ~ 15.7g

Sodium Hydrosulfide

Sodium hydrosulfide is a useful chemical for synthesizing organic thiols. It is used for making mercaptans as well (very smelly substances). It is often produced in small scale by the action of hydrogen sulfide on sodium methoxide. Unfortunately, sodium is hard to come by, even more so for making something like this. The alternative route is to bubble the hydrogen sulfide in a sodium hydroxide solution. I will discuss the latter.

H2S(g) + NaOH(aq) ----> NaHS(aq) + H2O

Set up your reaction system. It would be advisable to daisy chain many implements together. If you click on the 'daisy chain' link, you'll see the set up I used. The first flask, on the left, is where the hydrogen sulfide is generated - using paraffin and sulfur. The next small flask is a backflow trap. Due to temperature changes, liquids can sometimes be sucked back. If this were to happen, and flow into the very hot hydrogen sulfide generator, it could crack it. The next vessel (the third from the left) is a 100ml graduated cylinder. This has the sodium hydroxide solution in it. The last two flasks are filled with a hydrogen peroxide solution. This is to neutralize the excess hydrogen sulfide, due to it's toxic nature, by turing it into elemental sulfur and water. For the reason I used a graduated cylinder for the reaction flask, go to gas reactions.

Prepare a sodium hydroxide solution using 20g sodium hydroxide, and water to make 100ml. Mix it in an Erlenmeyer flask (or similar) and then add it to the 100ml graduated cylinder. Be sure there is adequate room, as the fluid will raise a good 10-20ml. Put the stopper on, and begin purging the set up with nitrogen gas, or a noble gas. It is not absolutely necessary to purge it, but your sodium hydrosulfide will be contaminated with poly sulfides if you don't. You can not use carbon dioxide, as that would react with the sodium hydroxide. Once it is all leak tested, begin adding the hydrogen sulfide. 20g of sodium hydroxide will need slightly more than 1/2mol of hydrogen sulfide. Be sure to use lots of excess (around 1mol). If you are not doing this in a fume hood, or outdoors, leave the area now. Hydrogen sulfide is very poisonous.

Hopefully you used a decent excess of hydrogen sulfide (about 1mol or more). If so, the reaction should be complete once the hydrogen sulfide generator is running out. If there is no visible reaction taking place with the solution any longer, and there are very few bubbles, stop the generator. Once it has cooled down, and sufficiently stopped, disconnect it and cap it. Begin disassembling the set up (watch out for residual hydrogen sulfide). Pour the solution into a 600ml beaker, and add 100ml or so of distilled water. Boil this down to rougly 75-100ml, then place it in an evaporating dish. Evaporate the remaining liquid out. Once it is dry, it would be wise to recrystalize from boiling ethanol. This should take rougly 100-150ml. Sodium hydrosulfide is hygroscopic, so evaporate any moisture as necessary, then store it. Theoretical yeild is about 28g (anhydrous!). Since this is sodium hydrosulfide hydrate which we are producing, it will be yellow in color, and theoretical yeild is around 37g. Some decomposition will occur from the boiling step, so you'll be left with hopefully more than 25g. The last time I did this, I had a yeild of 28.5g which is a 77% yeild.



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