raivo

Any alkane (or mix of alkanes) with low boiling point should do the thing.

I too can access it without any problrems. Do you use right address http://www.sciencemadness.org/ and for forums http://www.sciencemadness.org/talk/? Maybe you used https instead of http with computer that is not configured for secure http. As far as i know they have not blocked any ip -s and should be available from everywhere.

to speakerguy: Anodized aluminium is not suitable with any kind of electrolyte as far as i know. It gets oxidised by acid or salt electrolytes and imepedance of cell rises to kiloohms or even more. This is in fact how common electrolytic capacitors are made. In alcaline electrolytes Al just dissolves with evolution of extra hydrogen. Stainless steel may be best you can get. In this case NaOH must be used as electrlyte. Another way is to find some large graphite plates. These are used in industrial electrolysers and might be available. In case of graphite you can use acid or salt electrlytes as well but current density must be lower. Otherwise graphite my pulverise with fast rate. Your computations on resistor based current controll are ok but more practical way is just to get some power supply that has low output voltage and high current rating. Even 3V should be enough and amperage limit should be as high as possible. In industries they use kiloampers for single cell. That of course means that electrode surface must be 1m2 or more. Power supply does not need to be precisely current controlled (although this is good) but it should surely be current limited so that you do not need to worry when cell resistance drops to unexpectedly low level. In industries they use switchmode PSU-s specially designed for this purpose. Powerfull transformes (similar to those that are used for electrical welding) can also be used if suitable recitifier (4 power diodes) is aded. Hobby chemists usually use computer PSU-s or car battery chargers. But as i said there must be series resitors or some other tricks to protect PSU if cell wants to draw dangerously high current. to jdurg: good that you pointed this out. I have not played with platinum myself and did not think of its catalytic properties. It still can be used in hydrogen-oxygen producing cells (and is sometimes used) but it seems that cell must be carefully designed to prevent any mixing of oxygen and hydrogen.

I want to add that one of most serious problems you will encounter when using electrolysis is destruction of electrodes, especially anode. So you indeed need to use low current densities and anode must be made from graphite and better yet from platinum. In my opinion NaOH is better to use than acid or salt electrolytes as this gives you another choice of electrodes - you can use iron or stainless steel and this wil not corrode much if electrolyte is NaOH solution (aprox. 10%). Indeed you need to use low voltage power supply. This is a must because even if you get cell resistance high enough to use, say 220V then excess voltage (everything that is over some volts) just gets converted to heat. So if you put 10A @ 220V through your cell something like 3V x 10A = 30W does your electroolysis and 217V x 10A = 2.17 KW starts to heat your electrolyte. So you get boiler instead of electrolyser.

It can be used to grow nice crystals easily. As drying agent it is sometimes better than CaCl2. It can be used for electrolysis experiments, as source of sulfate ions or for etching (or dissolving) some metallic anodes. It can also be used to make other magnesium salts by first precipitating it with alkali metal hydroxide or carbonate and then reacting with suitable acid.

Thanks woelen. What if to use H2O2 without sulfuric acid? Do you think this will work? Or what if we use some other acid instead of sulfuric? I still suppose that sulfuric acid may be unsuitable for this kind of oxidation. Toluene gets easily sulfonated, this may affect end products. 85% sulfuric acid at room temperature sulfonates it in great extent when left to stand for some weeks. First crystalls of sulfonic acid can sometimes be seen few hours after liquids are put together. At higher temperatures sulfonation goes much faster.

Do you (Woelen and YT) are absolutely sure that sulfuric acid is added to potassium permenganate when oxidising toluene? I did more research in my papers now and i found two books where this synth is described. Both are without sulfuric acid and theoretical yield is said to be aproximately 3g benzoic acid to 10g permanganate. According to equations one molecule of toluene needs 2 molecules of KMnO4 to get oxidised. I would be very interested in cheaper ways for organic oxidations as permanganate indeed is expensive. Maybe KNO3 could be used someway? Anyone knows?

I made benzoic acid this way: 4.1ml toluene 10.2g potassium permanganate 225ml water this mix was boiled with reflux condenser without stirring during 4 hours. Liquid part was separated by filtration and evaporated to 30ml volume. Aproximately 5ml of 22% HCl was added dropwise to this almost clear liquid. White precipitate immediately formed. Precipitate was collected by filtration and was left to dry. I got 2.1g benzoic acid although i was expecting aproximately 3g. These data are from my lab notebook. Amounts are those what i used and need not be exactly those what i found from org chem books when planning this synth.

Cr2O3 indeed can be dissolved in molten NaOH but there is one more problem with it. When quite small quantity of Cr2O3 (and also products of reacting it with NaOH) are dissolved in molten NaOH then melting temp goes up and this mass becomes solid and reaction stops. In reality just small amount of Cr2O3 in quite big amount of NaOH can be dissolved this way. Results are much better if oxidiser (usally KNO3 or NaNO3) is added to initial mixture. Industrial process uses Na2CO3 instead of NaOH. This is mixed with small dolomite pieces and heated to 800C (or even more) with constant stirring and good aeration for some hours. Sodium chromate is made this way and this can easily be convertod to dichromate or chromic acid. If i recall correctly Cr203 thermite needs 800 - 1000C preheating for reaction to run. Ignition temperature is even higher.

Why not buy some of that mineral acid? It should not be hard to do some tests that will show what it is.

This abstract does not seem very scientific. It looks as if authors want to prove that substance they were talking about is something different of common water and there is very litle info on actual properties of this substance. In place of short description how it is made and separated we will find just that samples are available. Maybe this is not fake but bunch of enchancements to already known things. There are gas generators that decompose water vapour with heat (incadescent chrome-nickel wire will do this). This way can much greater volumes of combustible gas made than with electrolysis. Maybe they just combined this with electrolysis and added some minor discoveries with high energy magnetic fields? Is new form of water actually needed to explain these results? Lets wait and see.

Man needs dangers to be happy. Chemistry may be rather dangerous but there are lot of fully respected acctions that are not less. Such as surfing in the sea or or climbing in montains or some kinds of wintertime fishing. There are also lot of dangerous things that everyone does as this is required part of our lives. Walking in the streets is rather dangerous and driving a car is even more. And when living in big city we all are continously intoxicated with bensene and milions of other toxins. Smokers get even more of this. And after all - governments who claim that theyr biggest concern is our safety have floated this world over with numerous kinds of bombs in so big amounts that everyone of us can be burnt or riped into pieces thousands of times. What i want to say is that hobby chemistry is not something especially dangerous when compared to other dangerous parts of human life and it is probable that if all the dangers of our life are eliminated in some mystical way then amount of suicides will increase greatly because many would feel that theyr life is empty.

To Xavier: Most of your arguments are of such kind that one can not say you are wrong. Its question of general attitude. One can also say that guns are dangerous and widely used to make crimes. How others can know that particula gun-owner does not intend crime or that He/She is responsible enough in every state of mind? Almost the same can be sayd about cars or knifes and many many other things. Even common glass bottles have been used to kill a man and can hurt if carelessly or improperly used. I do not have proper statistics at hand but accidents by using lab chemicals at home are probably rarer than most other kinds of accidents. There are some very dangerous chemicals that can never be effectively banned becuse they are needed in everyday life. Gasoline and nitrate based fertilisers for example. If one wants to blow something up then there will always be some chemicals available that he can use. Bad deeds should be a crime, not ownership. It should be work of police and courts to make it clear who does bad things and who does not. Todays tendency on law-making (to make ownership a crime as it is done with red phosphorus) shows us that policeman want to make theyr work a lot easyer. Amateur chemistry is kind of hobby like fishing or hiking that one just can not ban it. Those who like it will do it anyway. Proper way would be to make laws that let to do it more safely with budget that home chemist can use. Restrictions will make this hobby just more dangerous.

I have done benzoic acid by potassium peramaganate oxidation of toluene. If i recall correctly i refluxed solution of potassium permanganate for 4 hours with small quantity of toluene. After filtering and evaporating got white powder with almost no smell but dust was very irritating. It made me cough if prespired even in smallest quantities. I assumed that this is benzoic acid. I used it to make esters. It can also be used to make benzene by dry distillation. Toluene can be chlorinated to make benzyl chloride which is quite remarkable intermediate in organic synthesis. Edit: Just remembered some more details... After filtering and evaporating most of water i added some HCl. Benzoic acid precipitated. Precipitate was collected by filtration and dryed to get that white powder which i used to make esters.

Very small quantity (like 5ml) of HNO3 can be made with corck stopper without ptfe or other special protection. I have done this several times. Sometimes cork stopper lasts even more than one experiment.

There are many books that contain lot of syntheses. Such books usually have word "practical" in title. In organic chemistry the best is probably Vogel's "Textbook of Practical Organic Chemistry". Another synthesis book is "A Course in Inorganic Preparations" by Henderson and Fernelius. Even better book is "Inorganic Laboratory Preparations" by Schlessinger.

This is Bromothymol Blue.

woelen, i do not know for sure but i suppose that several LM317 based current sources can be paralleled for higher current. I do not see any reason why this should not work. Proper cooling is required of course otherwise even LM317 will die.

If you can find potentiometer that can be used at 10W (better still 30W) then you can use it. Otherwise it does not last long. Those lm317 's are cheap (just looked in ebay - $2.49 for 10pcs), buy some, there is a lot to do with them.

It depends. Computer power supplyes are not simple transformer circuits. Switchmode converters are used that relay on inductors and contain quite complex circuits. I have seen computer power supplyes that have multiple 5V modules inside that CAN be paralleled for higher amperage. There are others that can supply almost all output power to any output rail if other rails draw no current. It depends on circuits and is impossible to tell just by description. 3.8A is a bit low for normal PC. So there may well be other 5V rails that can be paralleled. Nevertheless 3.5 A is not too low for electrolysis experiments. In my opinion its better to stick with that for some time.

Easy way for higher current in your case is to put some of those 10W 10 ohm resitors in parallel. Each one will give additional 0.5A. You can step to 3.5A such way - no more as 3.8A is limit of your power supply.

If you want to make your own power supply you have to get suitable transformer at first. This must be rather powerfull not like those in telephone chargers but much bigger. Output voltage of the transformer must also be suitable. Something form 15 to 25V is good. You need 4 diodes and big electrolyte capacitor to convert voltage from transformer output to DC. When converting to DC voltage will go higher - aproximately 1.4 times compared to AC output. This must still remain less than 40V otherwise you can not use simple circuits with common LM317. If this all is done then connecting LM317 as voltage or as current regulator is very easy.

HCl can be made by mixing H2 and Cl2 but as jdurg sayd these will not react but may explode even if intense light falls suddenly onto the mixture. H2 and Cl2 can be safely reacted if reaction vessel is small and contains sparkgap that ignites mix of gases as soon as there is anything to ignite. To make HCl from H2 and Cl2 is not practical because in real world chlorine tends to be more expensive than HCl. I make mine by recting HCl with KMnO4.

PC power supply is best you can get if you are in low budget and can not wire your own. Best for lab use are old AT ( 286 type PC ) power supplyes that were in wide use 10 ... 12 years ago. Most of these will survive any short circuit (they just switch itself of) and you have choice of 12V and 5V rails (some even have 3.3V rail). ATX power supplies and other modern devices are generally less foolproof and usually require some extra connections to work at all.

When reacting metals with acid there are sometimes strong smells that are not smells of acid i have used to work. At least this is what i have experienced. Some books say that metals contain small amounts of phosphorus, sulfur and arsenic. I suppose these will react with acid and so we get some microscopic amounts of very toxic (and strong smelling) gases. It probably is not especially dangerous because of extremally small amounts but its nevertheless good idea to do such reactions in fume hood.