Wikipedia:Reference desk/Archives/Science/2015 September 21

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September 21

What is the lifespan of leukocites?

I read on the book Basic "Medical Laboratory Techniques" (p.100) that "Leukocytes have varied life spans, from a few days to several years." Is that right? When I read our article I saw that is years for a memory cells. What does it mean "years"? years can be 2 as well as 80. I would like to get information about this issue. Thank you. — Preceding unsigned comment added by 37.73.202.15 (talk) 01:57, 21 September 2015 (UTC)

That much variation makes me think they have no fixed lifespan, but rather survive until something kills them. So, if this is the case, there might be no maximum lifespan, other than the maximum lifespan of the organism (and I suppose they might get around that as the result of transfusions). StuRat (talk) 03:51, 21 September 2015 (UTC)

One study reported lifespans of at least 17 years and half-life of 11 months for effector CD4+ T cells. They looked at HIV infected cells, don't know if the virus may have effected the life-span... Ssscienccce (talk) 10:54, 21 September 2015 (UTC)

If my understanding is correct, memory B cells and memory T cells are where active immunity is "stored", so that implies they can live at least as long as the organism they're a part of, since immunity can be lifelong. --71.119.131.184 (talk) 18:27, 21 September 2015 (UTC)

Not if they can reproduce to form two daughter cells with the same "memory". StuRat (talk) 22:32, 21 September 2015 (UTC)

That's true, but I believe they only divide when stimulated, either directly by antigen, or indirectly by other immune cells. If not activated, they just sit around in the body. This is why you can lose immunity, because eventually all the memory cells for a particular antigen may die or become senescent. Again, I think this is correct based on what I've read, but I'm not an expert. --71.119.131.184 (talk) 00:03, 22 September 2015 (UTC)

Diagnosis of schizophrenia (critique of the diagnosis)

There was a article with a name similar to the above that disappeared from the Wikipedia several months ago. It was an article critical of this psychiatric diagnosis, and deservedly so, since there is a substantial amount of scientific evidence and scholarly writing to put the construct in doubt. I would like to know what happened to the article (if it was deleted, if it was renamed) and the process involved.Spinheel01 (talk) 04:03, 21 September 2015 (UTC)

Maybe it was just renamed. There is still Diagnosis_of_schizophrenia and Diagnosis_of_schizophrenia#Controversies.--Llaanngg (talk) 04:08, 21 September 2015 (UTC)

Perhaps Social construction of schizophrenia? Ssscienccce (talk) 11:25, 21 September 2015 (UTC)

Thank you for responding. Those two articles are completely different from the missing one and that is my concern. The missing article, which cited numerous peer-reviewed publications, presented a critical view of the psychiatric diagnosis and the DSM in general. If this page is gone, proponents of the prevailing biomedical approach will have successfully purged the alternative perspective from Wikipedia. I thought this type of bias and censorship is exactly what Wikipedia, as an open encyclopedia, was designed to prevent. Spinheel01 (talk) 14:01, 21 September 2015 (UTC)

Not every opinion someone holds is Wikipedia-worthy. Wikipedia has rules such as WP:FRINGE and WP:MEDRS upon what's allowed as medical claim. This is "The free encyclopedia that anyone can edit." It isn't an "anything goes" forum for crank science (see WP:ABIAS). Tgeorgescu (talk) 22:20, 21 September 2015 (UTC)

E.g. even Thomas Szasz stated that anti-psychiatry is a sham. Tgeorgescu (talk) 22:30, 21 September 2015 (UTC)

I don't think it is controversial or fringe to argue that schizophrenia is a social construct. What counts as AIDS and what counts as pre-AIDS HIV is partly arbitrary but that doesn't mean AIDS isn't any less real or deadly. The disease epilepsy is also a catch-all diagnosis for many different unrelated things but it is still real. Sexual orientation is hard to define and is a human invention, not any less real. Of course we can debate things like Szasz and the right to be different when it comes to schizophrenia but that's unrelated. Andrea Carter (at your service | my good deeds) 23:30, 23 September 2015 (UTC)

There is, as you point out, a difference between socially constructed and bogus. It is true that the criteria for diagnosing schizophrenia were arrived at through medical consensus, which is a social process, but that does not mean that the diagnosis would be bogus nor that treating schizophrenia would not help patients. Tgeorgescu (talk) 14:39, 24 September 2015 (UTC)

I have reviewed the Wikipedia rules cited above and I reject the claim that the article in question should have been removed based on these criteria. First of all, the material referenced numerous articles that were published in established, peer-reviewed journals or books printed by reputable publishers, including university-affiliated presses. Second, much of the information reported was secondary research culled from original articles published in prestigious, mainstream psychiatric journals (e.g., American Journal of Psychiatry, Archives of General Psychiatry). This secondary research collected findings that revealed the weak and almost nonexistent scientific evidence to support a biomedical model of behavioral or mental disorders and the frequent failure of drug treatments for these problems. Most psychiatrists are dimly aware of these shortcomings, but this information is rarely made available to patients and the public. The accusation of "crank science" is merely a ploy to dismiss and censor research revealing the serious flaws in this belief system.

However, I have been distracted from my original question: Was the article in question deleted, and if so, who deleted the article and under whose authority? Can this action be appealed and reversed? At the present moment, Wikipedia only represents the prevailing biomedical perspective, which is currently undergoing intense criticism from social and behavioral scientists, mental health professionals, and former mental health service consumers both in United States and internationally. Wikipedia is at risk of falling out of touch with an important social movement and common public knowledge.Spinheel01 (talk) 03:06, 22 September 2015 (UTC)

To even know why the article was deleted, and how/whether that decision could be appealed, we first need to know where the page was located. If you could remember anything about the page such as its exact title or who wrote it, that may help tracking it down. Unfortunately there is a technical flaw with the MediaWiki software that Wikipedia is built on, which prevents searching the database of deleted pages. Any editor can pull up the deletion log of a page if they know its title, and as an administrator I can pull up such a page's former content, but no one can search for a term and have returned a list of deleted pages that use that term in the body or title. Someguy1221 (talk) 03:15, 22 September 2015 (UTC)

Anti-psychiatry, Causes of schizophrenia, Critical Psychiatry Network, Biopsychiatry controversy? Controversy surrounding psychiatry was split from the Psychiatry article three months ago.

You can search Articles for deletion discussions: https://en.wiki.x.io/wiki/Special:Search?search=schizophrenia&prefix=Wikipedia%3AArticles+for+deletion%2F&fulltext=Search+archives&fulltext=Search

Search of deleted articles is here: https://en.wiki.x.io/wiki/Special:Log/delete but needs exact name. and browsing through the list of deletions doesn't seem a realistic option, must be 2 or more per minute, by the looks of it..

If you came across the article from an outside link, on a blog for example, that link would tell you the name. :I've searched the WikiProject Medicine for "schizophrenia", but no mention of an article deletion.

Options depend on how sure you are it can't be one of the others where the content is removed. If not sure, you could check the history of the pages. Ssscienccce (talk) 04:29, 22 September 2015 (UTC)

This is very helpful information. I appreciate your assistance. I will begin searching through these links for the lost article. Thanks again!64.13.120.128 (talk) 03:37, 24 September 2015 (UTC)

Maximum feasible speed for a space ship

What speeds are realistic for a space ship, and how much would these speeds dilate time? --Llaanngg (talk) 04:05, 21 September 2015 (UTC)

You are asking about theoretical limits, not the limitations of current technology, right ? If so, a spaceship that shoots matter out at the speed of light should itself be able to move close to the speed of light. The necessity of saving some mass for deceleration and stopping at the other end would mean it couldn't use quite so much of it's mass in the initial acceleration, so that would limit it's maximum speed. And, if a return trip is intended without picking up any more mass to use as propellant, then that would limit the max speed even more.

As for time dilation, keep in mind that it could take months or years to accelerate and decelerate at each end, especially if you want to keep it down to one g for human health reasons. So, the time dilation then would be minimal. Indeed, the passengers might spend more time in those two phases than in the much longer (distance-wise) cruising phase. StuRat (talk) 04:28, 21 September 2015 (UTC)

... and, of course, from the point of view of the occupants of the space ship, the speed does not affect time at all. In fact, when they are moving close to the speed of light relative to their starting planet, they observe their own time as normal, and that planet's time as slowed down. Effects in Special Relativity are symmetrical, though that fact doesn't contradict the reality of the twins paradox. Dbfirs 07:13, 21 September 2015 (UTC)

(ec) However, the time dilation near the midpoint can still be quite substantial. I read somewhere that a least-time flight to Proxima Centauri (that is, accelerate at 1g for the first half, then decelerate at 1g) would take about 6 subjective years but more than 7 as seen from Earth. A radio signal from Proxima Centauri would return to Earth just short of 12 years after launch. No twin-paradox-grade weirdness yet, but far from minimal either.

If you went to Vega (25LY), the subjective trip time would be shorter than the objective light-speed delay. - ¡Ouch! (^{hurt me} / _{more pain}) 07:28, 21 September 2015 (UTC)

My numbers were way off: https://books.google.com/books?id=u5B0CQAAQBAJ&pg=PA84 (image) shows it's only 7 years for the Proxima round trip. That's already less than the two-way signal lag as seen from Earth or Proxima. - ¡Ouch! (^{hurt me} / _{more pain}) 09:15, 21 September 2015 (UTC)

If the problem is realistic speeds - then we have to get into the rocket-science part. A ship that's capable of accelerating/decelerating at one g for years by throwing propellant out the back is going to need a lot of mass to throw out the back ("reaction mass") and a lot of energy to throw it with ("fuel"). In a typical rocket design today, the energy comes from the fuel and the reaction mass is just the waste product from that combustion - but there are other possibilities - you could, for example, imagine a rocket that used water as the reaction mass and solar panels to collect the energy to boil the water and use the steam to propel the ship forwards. That's not going to be an efficient design - but it simply illustrates the possibilities.

So to get a constant one g acceleration for years is a painful problem. If you just tried to use current rocket technology, you get into this horrible spiral where you need X amount of fuel to push the rocket - but you need more fuel to propel the fuel along with it, and yet more fuel to propel that fuel. It turns out that even for relatively modest goals (getting out of earth orbit and travelling to the moon - coasting for most of the way) - you need that gigantic Saturn V launcher just to take the lightest imaginable, teeny-tiny capsule and lander. That approach would barely give you a one g acceleration for a few hours...certainly not for years. So conventional rockets are off the table.

To get around that spiraling fuel demand problem, you have to understand that the faster you can push the reaction mass out the back of the rocket, the less reaction mass you need. So to sustain constant acceleration, you need to be pushing the reaction mass out as fast as you possibly can - faster than a conventional rocket can...but that still takes crazy amounts of energy. If you're going to avoid the "needing more fuel to accelerate the fuel" trap - you need to either resort to 'exotic' fuels like antimatter - or you need to provide the energy from outside of the ship...and that means using solar panels - or big lasers placed in orbit and fueled by lots of nuclear reactors or something. This is all tremendously difficult to achieve. Whether it passes your "realistical" test depends on your tolerance for doesn't-yet-exist-but-might-not-be-impossible technologies.

One of the more practical designs is to use an 'ion drive' which propels the reaction mass out the back of the craft at close to light-speed - this drastically reduces the amount of reaction mass you need to carry - but doesn't help with the energy source issues. Ion drives have very low accelerations - but are very energy/mass-efficient, so they can accelerate gently for very long periods of time using solar panels for energy and thereby eventually reach exceedingly high speeds...but once you get too far from the sun, the issue of providing enough energy is what kills you.

Another approach is solar sails - in this case, the space craft doesn't keep the reaction mass on board or the energy source - both come from sunlight (or perhaps massive orbital lasers). Light has mass (although not very much) so if you shine light onto a humungous mirror mounted onto the spacecraft, then the reflected light becomes the reaction mass to propel the ship. Using sunlight to do this through most of the solar system would require an insanely large mirror (the "solar sail") - but as you start to leave the solar system, the power delivered by the sun gets less and less - and the size of sail you'd need would soon be completely unreasonable.

One of the more crazy (but not entirely implausible) approaches is to build a space ship with an insanely thick curved metal plate at the back end - and to explode nuclear bombs against the plate to push the ship forwards. See Project Orion (nuclear propulsion) for details. This design has been studied very carefully - and it would be entirely possible to build such a thing if we had the motivation to do so. The problem with this design is that it's not very human-friendly - especially when it's launching! It could be made to produce 100g accelerations(!) - and get up into the fraction-of-the-speed-of-light realms rather quickly - but the crew wouldn't survive the experience. But by setting off a nuclear bomb every three seconds for ten days to produce a constant 1g acceleration, they could get to the nearest star within 133 years and reach 3% of light speed after the first ten days of acceleration. Such a ship would cost 300 billion dollars to build and launch...which is expensive - but plausible - Americans spend four times that much on health care every year, and if we built it over ten years (or with help from the other governments of the world) - we'd hardly notice the cost.

A similar design, but with matter/antimatter annihilation explosions could theoretically reach 80% of the speed of light...but we have no means to make, or store, anything like the amount of antimatter needed - so this is on the intersection of the "possible by the laws of physics" - and "impossible using practical technology" issues - and it's unlikely that it's ever going to be a practical engineering possibility.

I think it's safe to say that we have no known/reasonable way to propel humans to the nearest star and get there without dying of old age...but project Orion comes closest.

In my opinion, we could possibly get a lightweight probe to nearby stars within reasonable time/budget using an "Orion"-like spacecraft and allowing 100g accelerations. It seems more feasible to me to develop light-weight artificially intelligent robots that can tolerate crazy accelerations than to ever get an actual human there.

SteveBaker (talk) 12:37, 21 September 2015 (UTC)

Why is it theoretically impossible to produce and store large amounts of antimatter ? I understand the risk of a breach in the (magnetic ?) containment field, but we could build an automated production facility out by Pluto to negate that risk. (Of course, this technology would be centuries away.) StuRat (talk) 18:52, 21 September 2015 (UTC)

We currently don't have methods to make antimatter at rates that would let us power a lightbulb, so even putative methods for storing large quantities of antimatter safely cannot yet be tested. Someguy1221 (talk) 03:32, 22 September 2015 (UTC)

You're talking about practical tests, while I just asked about theory. StuRat (talk) 16:29, 22 September 2015 (UTC)

I was aware, but simply trying to point out that theory aside, we can't test our theories, so they are useless. Though perhaps that doesn't bother you. Someguy1221 (talk) 03:59, 23 September 2015 (UTC)

Are you sure that's true? According to our article on antimatter weapons, it would take CERN about 2 million years to produce half a gram of antimatter at current production rates, which would be enough for a weapon equaling Hiroshima bomb. Our article on TNT equivalency says that the Hiroshima bomb had an energy of 63 TJ. If we divide that by 2 million, that supposedly means that CERN is producing enough antimatter to produce about 32 MJ of energy per year. While this is not even a drop in the bucket compared to world energy consumption (something like 5.598 × 10²⁰ joules), it still seems like enough for at least a lightbulb. --OuroborosCobra (talk) 18:32, 22 September 2015 (UTC)

That's about 1 watt of power. The weakest incandescent light I'm aware of runs on 4 watts, which is obviously far weaker than your typical 60-100 watt lightbulb. Perhaps you could run a small LED. Someguy1221 (talk) 03:59, 23 September 2015 (UTC)

@SteveBaker: Can you really nuke even an "insanely thick" metal plate 2.5 million times and have something left? How do you dump the heat of part of a nuclear bomb in 3 seconds (steady state), without having your blackbody at the temperature of a pulsar? Is there any material that wouldn't be blasted to smithereens by the cumulative neutron flux? Wnt (talk) 19:12, 21 September 2015 (UTC)

Yes! Evidently...according to a bunch of very, very clever people who researched this to death in at least three different studies! See Project Orion (nuclear propulsion) for the US version of it and Project Daedalus for the British effort at a similar design. It's not a joke - it's a very serious consideration. You can certainly be 100% sure they thought of the more obvious objections, such as the plate being vaporized! There are actually some really complex calculations about how much time must be left for the plate to cool off between explosions, and how big the shock-absorbers have to be to protect the crew from the alternation of high-g acceleration and free-fall every 3 seconds! Those are actually the things that limit the rate at which the bombs can be set off. Anyway - if you haven't heard of it before - you should definitely read the articles. SteveBaker (talk) 20:09, 21 September 2015 (UTC)

Even with nuclear power, you can't keep 1g of acceleration for very long (at least, not enough to achieve the 90-something percent where relativistic effects keep the crew much younger than their families left behind on Earth). Therefore, it's not that important if it starts at 100g or 1g - the limiting factor is the delta v, and a longer acceleration phase won't hurt much. The mass of the shock absorbers would probably a more significant limiting factor than the fact that it takes you weeks, rather than hours, to get up to top speed. (It would be more important if you had a less damaging thruster capable of >1g, because you could use that as a lift-off stage.)

Moot point, though: The mass savings with an unmanned mission (smaller payload, no need for atmospheric containment, life support etc) would probably outweigh both of the above combined. - ¡Ouch! (^{hurt me} / _{more pain}) 11:20, 22 September 2015 (UTC)

Our article Tsiolkovsky_rocket_equation explains a bit about your second paragraph. SemanticMantis (talk) 13:02, 21 September 2015 (UTC)

Indeed, practical considerations limit the speed that can be reached by most propulsion systems.

Rocket mass ratios versus final velocity calculated from the rocket equation.

The rocket equation shows that the required mass ratio ${\frac {m_{0}}{m_{1}}}=e^{\Delta v/v_{e}}$ (m0=initial mass with fuel; m1=final mass) grows exponentially with $\Delta v/v_{e}$ , making velocities much larger than exhaust velocity prohibitively expensive. Slowing down (unless external forces are used) requires the same mass ratio for a given speed, effectively squaring the mass ratio required. If it requires a mass ratio of 1000 to reach a velocity, reaching it and slowing down again will require a mass ratio of one million.

Note that the rocket equation only specifies the propellant mass required, not the energy needed to propel the mass, or the engine and fuel mass needed to produce that energy. The most mass efficient engines theoretically possible, anti-matter propulsion engines, would reach no more than about 20% efficiency, the rest of the energy is lost in radiation and heat.

A 2003 paper by the Jet Propulsion laboratory discusses how such a spacecraft would theoretically be built. The result is a cylinder 600 km (400 mile) long with a diameter of 20 meters (65 feet). Most space is taken up by the 515 km long radiator, operating at 1200°C (2200°F), needed to cool the engine. How exactly the heat from the engine, caused by gamma radiation produced in the propulsion process, could be transferred to the radiator is unclear. A quick calculation shows that with the assumed energy flux of 210000 TW (more than the total solar energy hitting the earth: 137000 TW), the required temperature gradient in the Tungsten radiation shield for such a heat flux would be more than 10⁶ °C or °K per nanometer, a physical impossibility.

Production of the anti-matter needed, assuming the predicted maximum efficiency possible, would require 177 billion years with current human energy output.

"Realistic" space travel would exclude relativistic speeds, it seems. Ssscienccce (talk) 16:09, 21 September 2015 (UTC)

With periodic in-flight refueling, the greater time for acceleration required by human star travel at 1g is not a problem. The ship would simply utilize fuel and propellant from a fleet of robotic projectile/tankers that are each coilgunned from the solar system to increasing speeds in order for them to match the ship's speed at their rendezvous points. Ideally, the coilguns are also established near destination points to service the deceleration of client ships, otherwise it takes a long time for the slowest tankers to reach the ships from their departure point and have to be sent prior to a ship's departure. Unlike when carrying large quantities of fuel, the mass-energy requirement for the ship's deceleration is then identical to its acceleration. Absorption or deflection of interstellar dust would become important at some point, but there is no theoretical limitation or even practical limitation that I'm aware of to the ship's speed other than the vacuum velocity of light. As for the amount of time dilation, that does depend on the ship's speed in accordance with the equation

$\Delta t'={\frac {\Delta t}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}=\gamma \Delta t$

where $\gamma$ is the Lorentz factor. -Modocc (talk) 13:28, 22 September 2015 (UTC)

Also see our article on Space travel using constant acceleration, especially this section on the trip with respect to the ship's reference frame: according to which it takes 3.6 years to our nearest star and less than 24 years to visit other parts of our galaxy. :-) P.S. I advocated this coilgun-assisted in-flight refueling approach before, perhaps not as well, here and years ago on the BBC's chat pages though I'm surprised that this article does not explicitly mention it under its feasibility section. -Modocc (talk) 16:53, 22 September 2015 (UTC)

It's not just dust. The interstellar medium becomes hard radiation once you get to a certain speed. I don't know that it's an insoluble problem, but it's certainly not an easy one. --Trovatore (talk) 22:39, 22 September 2015 (UTC)

citation or reference to the chemical equation

Only my second time to ask a question for further information so may do this all wrong, but

Question. Could author of the statement, chemical reaction, cite a reference or addition detail to the chemical equation?

C5H10O5 → C5H4O2 + 3 H2O

from the article on Furfural, looking for additional information, specific conditions for the reaction

Also any additional information for the conversion to Furfuryl alcoholChem4Engr (talk) 05:56, 21 September 2015 (UTC)

I added a ref to the furfural article for this content, taken from the xylose article about he reactant mentioned in it. DMacks (talk) 06:50, 21 September 2015 (UTC)

Some papers:

• Production of furfural from xylose
• one-step production of furfuryl alcohol from xylose.
• Abstract of a paper describing higher yield conversion of xylose to furfural.
• Comparing two methods for conversion of xylose and xylal to furfural, with diagram of plausible pathways involved. Ssscienccce (talk) 19:28, 21 September 2015 (UTC)

"Waterproof" only not really

Why do waterproof clothing fabrics have a "hydrostatic head"? Why can't they just be actually waterproof like a plastic bag? --129.215.47.59 (talk) 11:59, 21 September 2015 (UTC)

Our articles Waterproof_fabric and waterproofing give some info. SemanticMantis (talk) 12:59, 21 September 2015 (UTC)

Thanks. I gather it's to allow evaporation of sweat. I'd rather rely on vents since I'm pretty sure the majority of moisture on my body when I peel off my "waterproofs" is rain. --129.215.47.59 (talk) 13:19, 21 September 2015 (UTC)

I wouldn't be so sure. Skin puts out lots of moisture, even when you don't think you are sweating. It just normally evaporates before you can notice it. StuRat (talk) 00:29, 22 September 2015 (UTC)

Disposal of medication

When medication is handed in at a pharmacy for disposal, does it all just go into a furnace or does it get sent different ways depending on knowledge about the content? Could the same thing be achieved by putting it in a biohazard bag at a life science lab? --129.215.47.59 (talk) 11:59, 21 September 2015 (UTC)

Biomedical waste may be autoclaved and sent to a landfill with regular trash. source

Old medicines handed in at pharmacies are probably incinerated; this seems to be the preferred method in the US:

Currently, high temperature incineration at properly permitted facilities is the standard for disposal of waste pharmaceuticals from hospitals, pharmacies, and drug company manufacturers. High temperature incineration completely destroys the chemical activity of the pharmaceuticals. source

I expect that incineration is also the standard method of disposal in other (Western) countries. It is the recommended option in the WHO report Guidelines for Safe Disposal of Unwanted Pharmaceuticals in and after Emergencies: "Pharmaceuticals are ideally disposed of by high temperature (i.e. above 1,200ºC) incineration". Ssscienccce (talk) 17:56, 21 September 2015 (UTC)

What detergents do you buy/offer the best value?

Do the cheapest dish and laundry detergents offer the best value or is it better to get the next thing up? I figure people scientifically-inclined may be less amenable to persuasion by marketing and consider the chemical contents of the products they're buying. For example the cheapest washing up liquid is lower viscosity but I don't suppose that necessarily mean it's less concentrated if the regular store-brand has a thickening agent.— Preceding unsigned comment added by Seans Potato Business (talk • contribs)

I'm afraid the purpose of this desk is not to give our opinions on our favorite detergent brands. If you are looking for good, tested product comparisons, let me suggest Consumer Reports, which has a reputation for scientific testing of products, and likely has done tests on the products you're looking at. --Jayron32 14:36, 21 September 2015 (UTC)

@Jayron32 it might be clumsily worded but I'd be inclined to consider this a legitimate question (the OP isn't naming specific brands). It could be paraphrased more neutrally as "do liquid soaps of different viscosities have different cleaning properties?". For laundry detergents, the main issues would be bio vs non-bio, which have different cleaning and dermatological properties; plus, some brands include a softening agent and some don't. For liquid soaps, thicker is always going to be better when it comes to washing dishes or hands, as you want the detergent to remain in contact with the surface rather than running down the plug. ‑ iridescent 15:33, 21 September 2015 (UTC)

Did I not direct the OP to a possible source to find the information they seek? Is that not the purpose of the reference desk? --Jayron32 15:44, 21 September 2015 (UTC)

Well, you directed him to a US publication which will have minimal relevance to someone in Maastricht (even when the brand names are the same, US cleaning products tend to bear little resemblance to their European equivalents, since the regulatory framework is different). I'm not sure that's really what he was looking for. ‑ iridescent 15:57, 21 September 2015 (UTC)

In that case This testing lab mentions they do their tests in The Netherlands, so that would be a good lead. --Jayron32 16:02, 21 September 2015 (UTC)

(EC) I mostly agree with Jayron32. BTW, I'm also uncertain how thicker dishwashing detergent is guaranteed to be better when you're simply diluting it as often happens with some methods of washing.

Perhaps most importantly, it seems the OP is missing a big factor, they have to define cheapest. (Edit: And note; they mentioned "less concentrated".) For everything cheapest would have to be per some unit, since it makes no sense to talk about a $1 bottle of soap with 500 ml as being cheaper than a $2 bottle of the exact same soap with 1.5 L if you're looking for cost effectiveness.

But, particularly for laundry detergents, your unit probably shouldn't be volume or weight. I don't know about where the OP lives, but here in NZ manufacturer recommend volumes for washing can vary quite significantly. (For liquid detergents they normal use the cap, for powders a scoop but how much these can fit vary, and some even use two for a normal load.) Most, but not all, manufacturers publish "number of washes" figures on their containers which would be likely be the best way to define cheapest presuming you follow the manufacturers recommendations. (Edit: For those that don't, it's obviously possible to derive these figures empirically if you buy the product. And perhaps in other countries, it's the norm to specify the volume or weight you're supposed to use, which happens here occasionally as well although only generally with those that publish a "number of washes" figure.)

Now, the amount to use can vary depending on wash size and how heavily soiled the clothes are, and some but not all also recommend differing amounts depending on whether a toploader or front loader is used. So these factors will need to be considered too. Although most recommendations are fairly non descript, e.g. they say "large load" or "normal load" with no real explaination what they mean by this (e.g. 5kg of cotton clothes), and I don't think there's any standard for this.

One big complicating factor and the one Jayron32 touches on is that besides everything else, performance can vary. Your national Consumer Institute or similar may publish reports comparing performance (probably based on following the manufacturer's recommendations). Note that performance data tends to be complicated, it will often depend on the wash temperature, the type of soiling, the type of washing machine, the fabric of the clothes and probably other factors, it will often be the case that there's no universal winner. Alternatively, if you find your detergent doesn't work well, or you find you need to use significantly more than recommended but don't with another detergent, this should be taken in to account. Ultimately, how much you actually use and how well it works is what matters, not more abstract factors which may be quite removed from these.

Nil Einne (talk) 16:12, 21 September 2015 (UTC)

I Agree that Consumer organizations would be the best source of information, their tests show that price is not a good indicator for quality; often the products scoring best on "value for money" include both cheap and more expensive ones, and the same is true for those scoring worst. See for example here and here. I wonder if game theory or survival strategies seen in evolution could explain the relative lack of correlation between price and quality...

Picking the second cheapest might not be a good strategy in general (wine in restaurants comes to mind). Ssscienccce (talk) 18:53, 21 September 2015 (UTC)

Some marketing practices to watch out for:

1) The "concentration game". In the US, at least, there is no requirement that they describe the concentration of the active ingredient(s). So, they will come out with "triple concentrated" formula, and charge twice the old price. That seems like a good buy, so you go for it. Then, after a while, the "3X concentration" label disappears. If you call them to ask if this means it's no longer triple concentrated, they will tell you, truthfully, that it still is. But, once people stop calling, then they start reducing the concentration until they get back down to the original strength, and everyone is still paying double for it. Powdered detergents can't play with the amount of water they add, but they could still use cheaper fillers, like salt.

2) Just like other products, the size keeps getting smaller. This you could notice, if you read the label carefully every time, but most people don't. Then they might come out with a "super size" which is the original size, but at a higher price.

3) Sales, on the other hand, can be a good way to go on laundry detergent, as they can offer substantial discounts, and it's unlikely any will actually ruin your clothes or dishes. When one goes on sale, you might buy one unit, try it, and, if it works, buy more while it's still on sale.

4) You can actually have detergent that's too thick, in that it won't easily dissolve in water.

I've also used failed shampoo (shampoo that I bought then didn't like) as general purpose detergent, most often as body soap (I don't worry if my armpit hair lacks luster). Better than tossing it out.

For laundry I've taken to using just a small quantity of bleach, and no detergent. It's much less expensive, as I get bleach for US$1 a gallon. All my clothes seem to survive bleaching, except, for some strange reason, my socks. They fade dramatically if bleached, while the rest of my clothes might fade a bit, but not noticeably more than they would with detergent alone. And, most importantly, bleach seems to kill mildew, while normal detergent does not. I save up a load of socks and wash them with detergent. StuRat (talk) 18:32, 21 September 2015 (UTC)

If the OP does not live in a very hard-water area, he might find that ordinary cheap sodium carbonate works just as well. It does not benefit from multi -million dollars marketing (which cost money and so gets added the the retail price), because no supplier can brand it as their own invention. Also, for those that don't have access to main swage but just a septic tank, it doesn't mess up the bacterial break -down like what detergent do and so negates costly maintenance. So it can be much less expensive whilst also cleaning ones cloths. Also, it is hypoallergenic, so less costly visits to the quack for problems whose causes he can't put his finger on nor find a cure for. For those that live in prosperous cities, why wash your cloths. Do what everyone else does, throw your dirty cloths away and keep buying new ones.. That’s what my grandchildren do... “ but Grandpapa! I have already worn that dress once, I just can not let my friends me wearing the same dress twice – please buy me this one – it has a designer label that non of my other frends can afford – but you can, huh, my very very dearest Grandpa “--Aspro (talk) 20:25, 21 September 2015 (UTC)--Aspro (talk) 20:12, 21 September 2015 (UTC)

Here is where we should look to Hollywood stars as our example, since they each get married multiple times, presumably to get more wear out of those wedding dresses. :-) StuRat (talk) 22:03, 21 September 2015 (UTC)

One thing to keep in mind when using machines (dish washer or laundry) is that many are designed specifically for tablets or powder or liquid or gel and these are not always interchangeable. In particular, I've been told that using liquids or gels can cause build-up. Make sure you check with your manufacturer before switching cleaners. 99.235.223.170 (talk) 23:53, 21 September 2015 (UTC)