Talk:Desiccant

Hygroscopy, salt, and rice

The rice reference should be moved to a section on food hygroscopy and a new section should be added about dessicants in chemical processes. Jmldalton 20:50, 2 May 2007 (UTC)

• Isn't salt more hygroscopic than rice ?

— Preceding unsigned comment added by 212.143.106.185 (talk) 13:17, 6 August 2007‎ (UTC)

Personal use of dessicants – original research?

There is a paragraph regarding personal use of dessicants. Is this appropriate? Might be original research. —Preceding unsigned comment added by 129.128.204.252 (talk) 17:32, 11 September 2007 (UTC)

Eating silica---active desiccant

what are the effects of swallowing the contents of the small packets and athe benefits of drinking plenty of water? — Preceding unsigned comment added by 98.27.39.14 (talk) 15:44, 31 May 2008‎ (UTC)

Supposedly none. It's none toxic and not particularly reactive. You certainly shouldn't purposefully eat it however. Drinking water is supposed to counter the one immediate problem it might cause, in that it absorbs a lot of water; which it will continue to do inside your body. The ones that change colour when exposed to water are more dangerous, as they contain heavy metal salts; which are poisonous (often to the nervous system, e.g. lead and mercury salts cause brain damage, mercury chloride is particularly toxic). Neither can those metals be easily removed from your body, they don't metabolise out in your poo or wee but remain inside your body (usually for your entire life), making them an accumulative toxin. —Preceding unsigned comment added by 86.166.135.180 (talk) 13:37, 12 April 2011 (UTC)

Desiccant regeneration system?

A cost-effective, low-energy, continuous-cycle desiccant dehumidifier or desiccant regeneration system can be easily designed from off-the-shelf component parts.

Would anyone care to elaborate the above statement and tell me how this is possible? AFAIK from googling about this is that it isn't very easy regenerating desiccants.

— Preceding unsigned comment added by Grokking (talk) 04:01, 25 June 2008‎ (UTC)

A more current Google search shows that people buy jars/buckets, fill them with silica or even charcoal (should be using activated charcoal) and pierce holes on top. Some use fans to blow air across the holes as well. This constitutes for the cost-effective, low-energy, continuous-cycle desiccant dehumidifier but I'm not sure about the regeneration part (i.e. a fully saturated jar of desiccant would need to be removed and baked as mentioned below), unless replacing with new desiccant counts --Yelojakit (talk) 21:17, 31 May 2012 (UTC)

Is desiccant re-usable ? How is it dried to be re-used ? —Preceding unsigned comment added by 159.245.32.2 (talk) 20:48, 15 December 2010 (UTC)

It depends which you're talking about. Some drying agents used in chemistry labs (like sodium wires) aren't really worth recycling. But the more common ones around the house are usually fine or designed to be reused. Silica gel for drying flowers is an example. They even sell it with indicator in it so it goes ?blue? when damp and ?pink? when dry. To reactivate it, you simply empty it out onto a tray and stick it in a hot oven for a set amount of time or until the colour changes (if it's an indicator type). A number of salts can have the same thing done to them, like table salt. Most of the salts you get at home are already 'damp' in that they have picked up 'water of crystallisation'. If you put table salt in the oven and roast it for hours, it will come out much more brittle, opaque and it'll turn to dust when lightly ground. Unlike unbaked table salt, the grains of which are transparent and that tends to remain as grit. The baked salt will suck moisture out of things. It's important that you either tightly seal the freshly cooled result in a container or use it soon after it's cooled. The atmosphere contains huge amounts of moisture, which all drying agents will suck up or react with over time if left open. This is a major problem in chemistry labs.

The power strongest desiccants the general public come into contact with are NaOH (Caustic soda / lye) and concentrated sulphuric acid (both being drain cleaners). Realistically, they are far too difficult to even attempt recycling them at home. They both tend to corrode things and rot organic material. Meaning you need to think more carefully about how you plan to actually use them. In science labs, they're used in special glass desiccators with a mesh over the chemical for the sample's dish to sit on. Some of these are connected to vacuum pumps as well. Vacuum, whilst not a physical thing per say, will also dry things extremely well, but is again, complicated.

For a good list of drying agents, their ability and how to reuse them (albeit mainly aimed at chemistry labs), google 'drying agent selection guide' and click the first link. It's probably hosted by 'designer drugs' who've copied the table from elsewhere. But the content is still fine.

— Preceding unsigned comment added by 86.166.135.180 (talk) 13:26, 12 April 2011‎ (UTC)

Pseudo facts.

Desiccants aren't "chemically stable or chemically inert". P2O5 (phosphorous pentoxide, phosphoric acid anhydride) is often used as a dessicant IN THE CHEMICAL LAB, as are several alkali metals (such as sodium). These chemically react with the water. Sulfuric Acid (98%) is another common - and reactive dessicant. (These chemical reactions can be violent (explosive)). Although almost any desiccant warms as it absorbs water (exothermic), reversible desiccants are generally only mildly exothermic. Desiccants used in commercial packaging are usually inert (otherwise they wouldn't be safe to ship). Dririte is a trademarked name, dririte can be reused many times by drying it out in an oven (I wouldn't use a gas oven, burning gas gives off water), dririte turns color after it reaches a certain water content, but that level may or may not be acceptable - depends on application. Desiccants normally rely on air movement (or fluid mixing). Most molecular sieves contain heavy metals and shouldn't be used with foods or medicines (unless precautions are taken). In an air stream many dessicants become air-borne and pose a risk to the lungs. Lets see, what other nonsense does this article contain? Oh, silica gel or amorphous silica is used as a desiccant, crystalline silica (sand) is not. There are a variety of ways to measure effectiveness of a desiccant, they include speed of absorption, amount of water absorbed, and level of humidity that can be reached at any given temperature (for the common desiccants, the reactions are reversible - meaning they are equilibrium reactions with the humidity in the air and may become increasing ineffective below a certain humidity (this means the difference between a humectant and a desiccant depends on what you accept as being "dry"). Most desiccants are less effective at higher temperatures. Most desiccants are not suitable for situations which require rapid desiccation, especially physical absorbants (chemically reacting materials generally absorb much faster, but are limited since their surfaces tend to become covered with reaction products). I can't think of a desiccant which is not dependent on its surface area for effectiveness (speed). (Amorphous silica has surface areas measured in dozens or hundreds of square meters per gram). Some materials (humectants) can be both humidifiers and dehumidifiers. Some desiccants are less sensitive to relative humidity, but generally all are to some extent. So we have air (fluid) flow, temperature, humidity and type of desiccant as important variables. In some situations, the number of cycles of use and regeneration may be important, and most desiccants effectiveness diminishes with number of cycles. With very few exceptions most surfaces on Earth have water on them, often described as a layer of absorbed water, but this may or may not be an actual "layer". There are tables available to determine suitable materials (especially chemical mixtures) which can be used to control humidity to a given RH. (Althoght desiccants are typically assumed to remove "most" of the humidity regardless of RH, in practice this just ain't so).216.96.77.183 (talk) 20:36, 2 November 2015 (UTC)

not that some editors are illiterate...

…but whoever cannot tell the difference between absorption and adsorption should stay far away from articles such as this. The latter term presently appears nowhere in this article, which thus fundamentally fails.

The major supplier SorbentSystems.com puts it into small words and simple concepts —

Absorption is when a substance is chemically integrated into another. When you drink a glass of water, you are absorbing it, as the water becomes part of you.

Adsorption is when one substance is being held inside another by physical bonds. If you spill a glass of water on your shirt, it is adsorbed as the fibers will hold the water until heat dries out the shirt.

Most desiccants don't chemically combine with water or the other substances they're present to protect against. They capture them through adsorption, and stow them away where they can't cause harm to the product.

A desiccant packet could be said to absorb moisture, but the water is being adsorbed by the silica or clay or carbon or whatever. While some conjugation of adsorb appears 11 times in Silica gel, it is entirely absent in Desiccant.

FWIW: desiccants are used to control not just excess moisture, but volatiles as well, in part to reduce disagreeable odors. This is also completely overlooked.

And in the commercial world, molecular sieve is something entirely different from silica gel. They will be sold side-by-side, but nowhere have I seen silica gel called molecular sieve. Unless some credible scientific source can be offered up to support continuation of this confusion, all such ought be scrubbed from here and related articles.
Weeb Dingle (talk) 16:01, 27 January 2019 (UTC)