Wiki: Acid

[Andy Burns]

Ooops!

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Tabby saying something like:

Might be worth mentioning the cautionary tale of accidentally and unknowingly encountering it. Many modern cars have Viton hoses under the bonnet and a fire there will char the hoses. Unfortunately the charred hoses often have an HF acid component in them caused by the degradation of the Viton. Some unlucky buggers in breakers' yards and elsewhere have had HF burns from this.

[Spamlet]

--

The only safe advice for the DIYer on chromic is don't have anything to do with it. You cannot deal with the waste even if you can keep the stuff off your skin. I used to test a chromating tank and advise on any chemical additions that might be necessary. I wore a rubber mask, visor, and rubber gauntlets up to my elbows. We had separate tanks for waste disposal, but one day a charge hand rinsed his gloves in the sink. We later had a visit from a very irate water board official... chromium is one thing they definitely do not want down at the sewage works.

S S

[Spamlet]

pH does not really mean much in very concentrated chemical solutions: it is intended for situations in which water is still abundant. Concentrated acids are effectively dehydrated, rather than fully ionised aqueous solutions. Conc sulphuric acid is particularly 'dry', and has such an affinity for water that it is used as a dehydrating agent to remove water vapour from gases, and, if water is added to the acid, the reaction can be so vigorous as to be effectively explosive and extremely dangerous.

So the point that should be asked is not "What is the pH of conc HCl, or H2SO4 solutions?", but "Are HCl and H2SO4 *solutions* of the same pH equally 'dangerous'? But even then, we are not comparing like with like, and each chemical has its own properties in addition to its acidity, and it is these other properties that determine which acid we use for which purpose. As far as Levis are concerned, *any* conc of H2SO4 is very dangerous indeed...

S

[Bob Martin]

It was right in my head but I reversed "always" and "never" when I typed. Sorry!

[Tabby]

Perhaps that clear explanation could be posted on the talk page when its up. Is that ok with you?

NT

[Andy Burns]

The traditional rhyme might have an annoying American tinge, but it's difficult to remember it the wrong way round ...

"Do as you oughta, add acid to water"

[stuart noble]

Can't help thinking the whole thing is a non-starter in a d-i-y context

[Andy Burns]

Do schoolkids actually get to *do* chemistry thesedays, or just watch youtube clips of glowing splints being inserted into boiling tubes of potassium chlorate?

[geoff]

Death by dyslexia

[Spamlet]

Perhaps that clear explanation could be posted on the talk page when its up. Is that ok with you?

NT

Yes: and I've got a few more bits in the pipeline on this topic too, only it is a little difficult to get it in clear laymanish terms.

S

[Bernard Peek]

True. But the revised text still refers to Hydrochloric as the strongest acid. That's true in that concentrated hydrochloric acid has a lower pH than concentrated sulphuric or nitric. But both of those are far more dangerous so in a colloquial sense they are stronger.

[Spamlet]

I am endeavouring to explain in more detail elsewhere: briefly chemists' Strong refers to complete ionisation whereas layman's strong is the same as concentrated. The wiki needs to point out the difference. Concentrated HCl, as others have noted, is not as concentrated as concentrated H2SO4, because it is a relatively light gas and, after a certain conc it evaporates as fast as you try to mix it in: the solution is saturated at a much lower conc than can be achieved with sulphuric.

As chemicals, irrespective of their acidity (Strength) nitric and sulphuric are powerful oxidising agents, and this is where additional dangers lie, especially in their most concentrated forms.

To illustrate the point consider that *dilute* nitric acid dissolves iron very readily: its H+ ions can move around freely in water and rush up to the surface of the metal (as electricians know, metals are to most intents and purposes just big sources of readily available electrons) where they take an electron each, and join in pairs to bubble off as hydrogen gas. Various ions of iron (Ferrous; Ferric) are possible but let us just say that iron ions take the place of the H+ ions to make the solution balance again: dilute nitric is thus a very good dissolver of iron.

Conc ('fuming') nitric is a whole different ball game and should only really be used in a fume cupboard with care, but if you were to try dropping an iron nail into a beaker of it, you would be in for a surprise. Generally, the nail just darkens a little. HNO3 is such a powerful oxidising agent that H+ does not get a look in, instead a coat of oxide forms evenly over the metal and protects it from further attack: it is said to be passivated. This is a similar effect to that used in the more complex process of anodising aluminium - in diluted (~15%) sulphuric acid assisted with an electric current. I have passivated odd bits of iron in this way before, but the coating is not very tough so I would not recommend it for general rust prevention! (Commercial rust preventing solutions tend to use various mixtures of phosphoric acids for this.)

So the point is that chemicals all have their own unique properties, that may vary with their concentrations, in addition to properties they may have in common. Being a Strong Acid is just one property. Sometimes concentration is good: sugar above 65% concentration is a preservative: but if you ate a lot of it, it would be bad for you. Horses for courses.

S

[Tabby]

Next version...

==Precautions== Most acids are high risk chemicals. Several precautions are advisable with many acids. These don't all apply to vinegar & citric acid.

• Due to the potentially high risk involved, labels should be read and advice followed

• When diluting, never add water to acid, always add acid to water. Doing so is sometimes highly exothermic, and should be done a bit at a time, wearing safety specs. If done the wrong way the result can even progress to explosion sometimes. Exploding boiling acid is not an essential nutrient.

• Some acids used in DIY eat through skin rapidly. Wear suitable gloves

• When holding hold the bottle by the label area, so any unnoticed runs are on the same side, and that's not where you're holding it.

• Don't mix acid with bleach, the resulting chlorine is quite toxic.

• Don't mix acid with alkalis, excess heat is generated, and boiling spitting acid isn't a good idea.

• Some acids plus metal can generate hydrogen, which is explosive above 4% concentration.

• Suitable gloves & eye protection are sensible for some of the acids.

• In case of skin contact with all but the mild acids, wash for 10 minutes to minimise burning, chemical reaction & contamination. In case of eye contact, wash for at least 10 minutes and seek medical help promptly.

==Sulphuric Acid== [[image:H2SO4 98% 4170-3.JPG|right|200px]] A strong acid, sulphuric acid has many names, including vitriol, glover acid, tower acid, fertiliser acid, chamber acid, battery acid, dipping acid, mattling acid, electrolyte acid.

Uses

• Eats organic materials rapidly. Eats paper etc in seconds.

• Good for drains where the blockage is organic

• Density of 1.84 means it sinks to the bottom of blockages

• Lead acid batteries use high purity sulphuric acid of around 4M. Less pure drain cleaning acid is not usable for batteries.

• Strong desiccant

• Reaction with sugar produces carbon

• Reaction of hot concetrated H2SO4 with copper produces copper sulphate, a mould inhibiting antimicrobial.

• Reaction with zinc produces zinc sulphate, a mould inhibiting antimicrobial.

• Used industrially to remove rust

Risks

• 98% sulphuric acid drain unblocker is probably the most dangerous of the acids used in DIY. Put a drop on paper for a demo.

• Dangerous to skin & eyes

• Destroys cement joints in ceramic pipes

• Toxic

• Concentrated sulphuric acid can react violently with water

• In work situations all use of sulphuric acid must be assessed under the COSHH regulations.

• MSDS]

Purchase

• Upto 98% sulphuric acid is available as drain unblocker.

==Hydrochloric Acid== [[image:HCl 34% 4168-3.jpg|right|200px]]

• A strong acid

• Also known as spirits of salt, muriatic acid

Uses

• Eats cement & lime

• Cleans cement off bricks etc - but not off cement products

• Can also be used to descale ceramics, but it can discolour otherwise unnoticeable surface cracking

• 18% hydrochoric acid is used industrially to clean steel before coating ('pickling'). Spent pickling solution is sometimes then used as ferrous chloride.

Risks

• Destroys cement joints in ceramic pipes

• 34% HCl produces choking fumes and mist

• HCl is highly corrosive to skin, eyes, lungs etc, and toxic. Inhalation of too much of the fumes can cause death

• In case of skin contact, wash for 10-15 minutes. In case of eye contact, wash for 10-15 minutes, lifting both upper & lower eyelids regularly, and seek medical advice without delay.

• Incompatible with many substances

• MSDS]

Purchase

• Sold as brick acid, drain unblocker, and is a component of many patio cleaners.

• Available upto 34%

==Chromic Acid== Not normally used by DIYers, but occasionally used for extreme ceramic sink cleaning. Its exceptionally effective, but very toxic and should be avoided.

• Can set fire to organic materials like paper and skin.

• Disposal creates serious problems

==Hydrofluoric acid== Used to etch glass. A high risk acid that causes particularly bad burns, but only used in tiny quantities in diy, typically in little glass etching pens.

Also used in industrial horticulture to clean greenhouses.

Some synthetic rubber can produce HF when burnt, and occasionally people have needed amputation after handling burnt car parts.

==Sulphamic Acid== Also known as sulfamic acid, amidosulfonic acid, amidosulfuric acid, aminosulfonic acid, and sulfamidic acid

Uses

• Used to descale heat exchangers in heating systems

• Descale and clean metals and ceramics

• A component in some household descalers & denture tablets

Risks

• Lower risk than hydrochloric acid

Purchase

• Fernox DS-3 contains sulphamic acid, inhibitors, indicators & surfactant.

==Phospohoric Acid== Uses

• Used as rust remover. Turns rust into a stable black ferric phosphate. Often used as a gel preparation to enable it to cling to surfaces at all angles.

• Phospohoric acid is used as a food additive, E338.

• Sometimes used to remove limescale and cement stains.

• Sometimes used as a soldering flux

• Used commercially as a nutrient for irrigated glasshouse crops

Risks:

• Don't permit contact with bleach, ammonia or metals

• Safety data]

Purchase

• Sold in preparations known as rust convertor, rust remover, rust killer, naval jelly.

==Acetic Acid== [[image:Acetic acid 4159-4.JPG|right|200px]]

• Also known as ethanoic acid, acetyl hydroxide (AcOH), hydrogen acetate (HAc), ethylic acid, methanecarboxylic acid

• Concentrated acetic acid is called glacial acetic acid. It freezes at 16C.

• Acetic acid has a characteristic powerful vinegary smell.

Uses

• Vinegar is primarily dilute acetic acid, typically around 4-8%

• Vinegar cleans copper, copper alloys, brass, bronze - the runoff is toxic

• Diluted vinegar cleans glass & helps avoid smearing

• Glacial acetic acid is used to remove warts & verrucas, and the dilute acid for ear infections.

• Acetic acid makes copper acetate, a pigment and fungicide.

• Sometimes used with other acids as a descaler

• Food additive E260

Risks

• Acetic acid is corrosive, and at high strengths highly flammable.

• Overexposure to the fumes can cause difficulty breathing. This can easily happen at room temperature.

• Consequences of exposure can be delayed for a few hours.

• Fumes above 39C can be explosive

• Latex gloves don't protect against acetic acid, use nitrile ruber gloves.

• Safety info]

==Citric Acid==

• A weak edible acid

Uses

• Citric acid is a widely used food additive, E330

• Descaler for appliances that can't take more effective acids, eg kettles, washing machines etc.

• 2% citric acid makes a handy scale tackling bathroom cleaner. 6% can remove scale without rubbing Salt enhances the descaling action of citric to an extent.

• Appliance descalers in supermarkets are usually citric acid based, with or without another acid and corrosion inhibitor. Not a cheap way to buy the stuff.

• Citric acid can often substitute for lemon juice in recipes

Purchase

• Citric acid is sold as a bagged food additive in some foreign food supermarkets, or less cheaply in small boxes at pharmacies (much used by addicts).

• Irritant to skin & eyes. In case of eye contact, wash well for 10 minutes and seek medical assistance

• Corrodes copper, zinc, aluminium and their alloys

• MSDS]

==See Also==

• [[Detergent]]

[[Category:Cleaning]] [[Category:Chemicals]]

[geoff]

In message , Tabby writes

I think you need to reassess the dangers of Hydrofluoric, it's not the burns but what happens if it gets absorbed into the body which is dangerous

I feel a crusade coming on here

[Tabby]

Bit more on HF and sulphamic acid...

==Precautions== Most acids are high risk chemicals. Several precautions are advisable with many acids. These don't all apply to vinegar & citric acid.

• Due to the potentially high risk involved, labels should be read and advice followed

• When diluting, never add water to acid, always add acid to water. Doing so is sometimes highly exothermic, and should be done a bit at a time, wearing safety specs. If done the wrong way the result can even progress to explosion sometimes. Exploding boiling acid is not an essential nutrient.

• Some acids used in DIY eat through skin rapidly. Wear suitable gloves

• When holding hold the bottle by the label area, so any unnoticed runs are on the same side, and that's not where you're holding it.

• Don't mix acid with bleach, the resulting chlorine is quite toxic.

• Don't mix acid with alkalis, excess heat is generated, and boiling spitting acid isn't a good idea.

• Some acids plus metal can generate hydrogen, which is explosive above 4% concentration.

• Suitable gloves & eye protection are sensible for some of the acids.

• In case of skin contact with all but the mild acids, wash for 10 minutes to minimise burning, chemical reaction & contamination. In case of eye contact, wash for at least 10 minutes and seek medical help promptly.

==Sulphuric Acid== [[image:H2SO4 98% 4170-3.JPG|right|200px]] A strong acid, sulphuric acid has many names, including vitriol, glover acid, tower acid, fertiliser acid, chamber acid, battery acid, dipping acid, mattling acid, electrolyte acid.

Uses

• Eats organic materials rapidly. Eats paper etc in seconds.

• Good for unblocking drains where the blockage is organic

• Density of 1.84 means it sinks to the bottom of blockages

• Lead acid batteries use pure sulphuric acid of around 4M. Less pure drain cleaning acid is not usable for batteries.

• Strong desiccant

• Reaction with sugar produces carbon

• Reaction of hot concetrated H2SO4 with copper produces copper sulphate, a mould inhibiting antimicrobial.

• Reaction with zinc produces zinc sulphate, a mould inhibiting antimicrobial.

• Used industrially to remove rust

Risks

• 98% sulphuric acid drain unblocker is probably the most dangerous of the acids used in DIY. Put a drop on paper for a demo.

• Dangerous to skin & eyes

• Destroys cement joints in ceramic pipes

• Toxic

• Concentrated sulphuric acid can react violently with water

• In work situations all use of sulphuric acid must be assessed under the COSHH regulations.

• MSDS]

Purchase

• Upto 98% sulphuric acid is available as drain unblocker.

==Hydrochloric Acid== [[image:HCl 34% 4168-3.jpg|right|200px]]

• A strong acid

• Also known as spirits of salt, muriatic acid

Uses

• Eats cement & lime

• Cleans cement off bricks etc - but not off cement products

• Can also be used to descale ceramics, but it can discolour otherwise unnoticeable surface cracking

• 18% hydrochoric acid is used industrially to clean steel before coating ('pickling'). Spent pickling solution is sometimes then used as ferrous chloride.

Risks

• 34% HCl produces choking fumes and mist

• HCl is highly corrosive to skin, eyes, lungs etc, and toxic. Inhalation of too much of the fumes can cause death

• In case of skin contact, wash for 10-15 minutes. In case of eye contact, wash for 10-15 minutes, lifting both upper & lower eyelids regularly, and seek medical advice without delay.

• Incompatible with many substances

• Destroys cement joints in ceramic pipes

• MSDS]

Purchase

• Sold as brick acid, drain unblocker, and is a component of many patio cleaners.

• Available upto 34%

==Chromic Acid== Not normally used by DIYers, but occasionally used for extreme ceramic sink cleaning. Its exceptionally effective, but very toxic and should be avoided entirely.

• Can set fire to organic materials like paper and skin.

• Disposal creates serious problems

==Hydrofluoric acid== A high risk acid that causes particularly bad burns, life threatening poisoning on contact and extreme pain

• Only used in tiny quantities in diy, typically in little glass etching pens.

Uses:

• Used to etch glass.

• Also used in commerce to clean greenhouses.

Risks:

• Extremely corrosive

• A contact poison. Poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed.

• HF penetrates tissue more quickly than typical acids

• Symptoms of HF poisoning can be delayed

• HF interferes with nerve function, meaning that burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury.

• Once absorbed into blood through the skin, it reacts with blood calcium and may cause cardiac arrest. Burns with areas larger than 25 square inches (160 cm2) have the potential to cause serious systemic toxicity from interference with blood and tissue calcium levels.

• Poisoning causes severe pain

• HF chemical burns can be treated with a water wash and 2.5% calcium gluconate gel or special rinsing solutions.

• In case of skin contact, medical treatment is necessary, rinsing off is not enough. In some cases, amputation may be required.

• Hydrogen fluoride is generated by burning fluorine-containing compounds such as some synthetic rubber, Viton, polytetrafluoroethylene (Teflon)

• Occasionally people have needed amputation after handling burnt car parts.

==Sulphamic Acid== Also known as sulfamic acid, amidosulfonic acid, amidosulfuric acid, aminosulfonic acid, and sulfamidic acid

Uses

• Used to descale heat exchangers in heating systems

• Descale and clean metals and ceramics

• A component in some household descalers & denture tablets

Risks

• Lower risk than hydrochloric & sulphuric acids

• Solubility in water is moderate, limiting solution strength

Purchase

• Fernox DS-3 contains sulphamic acid, inhibitors, indicators & surfactant.

==Phospohoric Acid== Uses

• Used as rust remover. Turns rust into a stable black ferric phosphate. Often used as a gel preparation to enable it to cling to surfaces at all angles.

• Phospohoric acid is used as a food additive, E338.

• Sometimes used to remove limescale and cement stains.

• Sometimes used as a soldering flux

• Used commercially as a nutrient for irrigated glasshouse crops

Risks:

• Don't permit contact with bleach, ammonia or metals

• Safety data]

Purchase

• Sold in preparations known as rust convertor, rust remover, rust killer, naval jelly.

==Acetic Acid== [[image:Acetic acid 4159-4.JPG|right|200px]]

• Also known as ethanoic acid, acetyl hydroxide (AcOH), hydrogen acetate (HAc), ethylic acid, methanecarboxylic acid

• Concentrated acetic acid is called glacial acetic acid. It freezes at 16C.

• Acetic acid has a characteristic powerful vinegary smell.

Uses

• Vinegar is primarily dilute acetic acid, typically around 4-8%

• Vinegar cleans copper, copper alloys, brass, bronze - the runoff is toxic

• Diluted vinegar cleans glass & helps avoid smearing

• Glacial acetic acid is used to remove warts & verrucas, and the dilute acid for ear infections.

• Acetic acid makes copper acetate, a pigment and fungicide.

• Sometimes used with other acids as a descaler

• Food additive E260

Risks

• Acetic acid is corrosive, and at high strengths highly flammable.

• Overexposure to the fumes can cause difficulty breathing. This can easily happen at room temperature.

• Consequences of exposure can be delayed for a few hours.

• Fumes above 39C can be explosive

• Latex gloves don't protect against acetic acid, use nitrile ruber gloves.

• Safety info]

==Citric Acid==

• A weak edible acid

Uses

• Citric acid is a widely used food additive, E330

• Descaler for appliances that can't take more effective acids, eg kettles, washing machines etc.

• 2% citric acid makes a handy scale tackling bathroom cleaner. 6% can remove scale without rubbing Salt enhances the descaling action of citric to an extent.

• Appliance descalers in supermarkets are usually citric acid based, with or without another acid and corrosion inhibitor. Not a cheap way to buy the stuff.

• Citric acid can often substitute for lemon juice in recipes

Purchase

• Citric acid is sold as a bagged food additive in some foreign food supermarkets, or less cheaply in small boxes at pharmacies (much used by addicts).

• Irritant to skin & eyes. In case of eye contact, wash well for 10 minutes and seek medical assistance

• Corrodes copper, zinc, aluminium and their alloys

• MSDS]

==See Also==

• [[Detergent]]

[[Category:Cleaning]] [[Category:Chemicals]]

[Spamlet]

Most acids are not high risk chemicals - many of them are essential in our food, many are vital parts of ourselves eg DNA, and some are vitamins eg vitamin C. However, those acids that are of particular use in the D-I-Y realm are often chosen *specifically for* their powerful and therefore potentially dangerous properties.

Vinegar is not an acid just the name of one solution of an acid - it just means sour wine -, it is a dilute solution of Acetic Acid. Though not by definition a Strong Acid, *concentrated* AKA 'Glacial' acetic acid is nasty stuff in its own right.

You need to point out the difference between Strong Acids and strong solutions: A Strong Acid - sulphuric, nitric, hydrochloric, - is one that is fully ionised in water, making high concentrations of H+ ions available for reaction. A 'Weak' Acid - like acetic or citric - is one that is not fully ionised in water, and so cannot make so many H+ ions available for reaction. The fact that something is a Weak Acid when dissolved in water, does not mean that a concentrated solution of it is not dangerous irrespective of its acidity. Many silicone sealants have quite concentrated acetic acid in them and they can burn you, even though this is not a Strong Acid.

Stirring carefully as you do so, so as to avoid over-concentration in one spot: this could have the same effect as pouring water into the acid. (And the same is also especially true with solid alkalis like Caustic Soda.)

If you are using any concentrated acid wear a full face visor.

Checking for holes by inflating them and holding under water first.

Wash the bottle down under the tap after you have resealed it.

Before holding, you have to get it to where you are holding it...

*When carrying acid containers, hold them away from your body, preferably in a metal, or strong plastic carrier like the old milkmen used to use. If you hold a typical 3 litre Winchester of sulphuric acid against your chest as you walk with it, and someone walks into you, or it simply breaks (I have had some 'safety' bottles where the glass was wafer thin in places.) it may kill you, and seriously injure others around you. *If your acid comes in a plastic container (same goes for alkalis), do not leave the container out in sunlight, and if there is more than one container, use the oldest first. It is both embarrassing and dangerous to find that a plastic container disintegrates when you go to pick it up, because it has been exposed to sunlight for too long. If you go to pick up acids that are stored outside at a suppliers, only go for those that have new unweathered labels: if they have had a run on their stock, the containers at the back, that you are left with may have been out for some time [Yes, it has happened to me.]

• Similarly, store your acids on the ground, on a surface that cannot get harmed by any leaks: if they were delivered inside a protective plastic drum, keep them in the drum.

The resultant chlorine is very toxic, and may kill you, especially so if you are an asthmatic.

*Don't mix concentrated solutions of acids and alkalis, and don't mix more dilute solutions, without careful stirring and waiting for any heat to be dissipated. You would normally only be doing this in order to render both solutions relatively safe by turning them into solutions of neutral salts. The Strengths of solutions of acids and alkalis are established by titrating the unknown with a standard solution of the known, and there is not usually much heat involved. *Do keep handy a quantity of a suitable neutralising agent to apply should you or your clothes come into contact with acids. Generally a dilute solution of bicarbonate of soda or washing soda, will prove effective, but specific acids such as hydrofluoric, or fluorosilicic - neither of which the DIYer should have anything to do with - require special chemicals kept in emergency stations. There should also be emergency eyewash kits to hand. (Similarly, with alkalis, it pays to have some dilute citric or lemon juice to hand to apply to any that gets on your skin: this also works for hands made 'slippery' with bleach.). If handling large volumes, have a shower or garden hose handy to drench yourself with.

In air.

Full face protection with a visor is preferable. You don't want to get specks on your face or hair that then get into your eye, even with the less dangerous acids.

See above: wash; neutralise: then wash again.

Conc Sulphuric may set fire to these (particularly, don't pour it on sugar...)

I would say NOT very good for drains: it will dissolve the cement holding the pipes together. Caustic soda solutions will dissolve most organic material that is likely to be in your drain, and they will not harm any iron or masonry parts. (Well, within reason: caustic solutions do slowly attack glass and hence glazed pipes, but you are not going to be using it enough to do any damage we hope.)

Density of 1.84 means it is 1.84 times as heavy as the same volume of water. It is also viscous, and like a thick bleach will adhere for longer to a blocking material, but in the small volume of water present this may be dangerous.

'4M' no need to get into molarity, say 30%

Do not hold such a battery against yourself and always wash it down after filling and putting the caps back on. Similarly wash it down after charging away from the vehicle. Always wear old synthetic clothes, and wash them afterwards.

But few DIYers will be in a position to use it as such, and it would attack most things they wanted to dry.

Better to put *hot copper* in *dilute* sulphuric acid. That is how we cleaned copper after annealing it at school, and at the end of term there were always nice big crystals to wow over.

NO DIYer should be *anywhere near* hot concentrated sulphuric acid: I wouldn't, without a fume cupboard on full extract with the glass safely down. This is SERIOUSLY dangerous stuff!

? Who by? It might be used to dissolve iron oxides to make ferrous solutions, but as it dissolves iron itself, it is not much use in the way one normally thinks of rust removal.

No: don't buy it in the first place.

*Scientifically speaking* 'Strongest': Strong here referring to the propensity for forming hydrogen H+ ions in water.

Get a proper eye wash station and have neutralising solutions handy.

DIYers should NEVER use this stuff, especially not for cleaning sinks, the washings contaminate the effluent and the treated sewage sludge then contaminates the land on which it is spread and your food is grown!

Get a vibrating tungsten scribe if you want to mark glass.

Never touch it: others have given good quotes as to why.

With lead it forms a sweet substance which made lead containing drinking vessels popular with the Romans, poisoning them in the process. For the same reasons one shouldn't drink cider from a pewter tankard.

I use 20% with a dash of washup liquid as a bathroom spray cleaner. I think

2% may be expecting a bit much.

Stainless steel swarf scourers can be put in kettles to collect the scale, which you can then rub off between your hands under the tap. No need to have scale on the kettle element in the first place.

[The Medway Handyman]

From experience One Shot (91% Sulphuric w/w) works where Caustic Soda fails misreably. Someone once told me that 80% of toilet blockages are paper based & caustic isn't very good at that, better at fatty deposits.

Its exceptionally effective albeit something I treat with great respect. I don't doubt its as dangerous as you say, you are obviously knowledgeable about the subject. How come the safety fairies allow it to be sold though? Even B&Q sell it!

[Spamlet]

Not sure whether you are referring to sulphuric or hydrofluoric here Dave. I would have hoped that B&Q wouldn't be selling any HF. In an older lab I first worked in, there were bottles of HF among the other common lab bench solutions, and indeed some of the 'old boys' did use it for labelling some bottles, and for bringing out the crystal structure of aluminium plate, but I doubt that you would find many labs like that nowadays. Later, I used to have to use the slightly less nasty fluorosilicic acid as an ingredient in an anodised aluminium sealing process solution. It came in small plastic dropping bottles inside protective plastic drums, and was always kept and used in a fume cupboard, which had a integral sink for washing any drips away immediately. And I was still scared of the stuff. (I was, incidentally, the safety officer: though I probably wouldn't know enough to pass for one nowadays..)

I did, for a time keep a small bottle of conc sulphuric in the garage - mainly to save the hassle of having bigger bottles of different concentrations, when I was experimenting with anodising (can't really get enough amps for this at home). But even kept inside a plastic drum, it still managed to attract in water, and the outside of the bottle was always sticky with it. It really isn't something you should have in the home. Drains are nearly always much quicker to take apart and clean by hand - with shoulder length rubber gloves if necessary - than with chemicals. In many cases it is the household chemicals like washing powder, that have caused the blockage, I usually find the garden hose clears most things, and in sinks and u bends it is usually hair that is the problem and this dissolves in caustic soda.

Another thing I noticed yesterday is that the lever pop-up plug in our bathroom basin had an alloy thread with a brass nut on the end as an adjuster. Now all that is left is the nut and it doesn't pop up any more. And all I've used in the basin is an occasional squirt of citric, and occasional bleach.

S

[Tabby]

B&Q selling HF? What's the product name?

NT