Sciencemadness Discussion Board

Helpful Hint for Beginners

UnintentionalChaos - 8-1-2007 at 22:23

This may be painfully obvious to some people, but I really didn't think of it until recently. If you need to filter a solution REALLY well and it is impossible to do using coffee filters (or filter paper if you're lucky/invested), cotton balls are very handy. Take an ordinary funnel and cram a cotton ball very tightly into the bottom where it narrows down. 500mls or so of solution will take hours to pass through this filter, but it will come out crystal clear. I just used it to remove some extremely fine ppted CuO powder that went through coffee filters, paper towels folded 8 times over, and everything else I tried :)

Like I said, this is probably laughably simple to most people, but not everyone (like me) finds it too obvious.

PS: If your solution somehow makes it through this still cloudy, a bit of diatomaceous earth (available for killing slugs and as pool filter material) and another cottonball to hold it in place should clear it up (Wear gloves when handling diatomaceous earth. If it gets on your skin you get the same horrible itching rash as if you rub up against insulation or are the unfortunate victim of itching powder (which is just finely powdered insulation to the best of my knowledge))

[Edited on 1-9-07 by UnintentionalChaos]

guy - 9-1-2007 at 01:12

I just discovered this a few days ago from reading Frogfot's instructions for dichromate synthesis. It works like a miracle.

Lambda - 9-1-2007 at 06:17

@UnintentionalChaos, I couldn't agree more with you, and maybe if I may add, @S.C. Wack too. For he has an intense love and interest for chemistry books of Nostalgia, in which all these very basic (and even long forgotten by many) procedures are described. In these old books, very easy and efficient/effective procedures are explained and used to there full benefit. We often tend to become a victim of high tech procedures and approach, in which supper fibre materials and techniques are involved. But when going back to basics, we not only make certain procedures simpler, but at the same time, make it more accessible, due to the ease of obtaining the basic materials involved. We often rely too much on the high tech environment in which our thoughts are manipulated, and channeled to think in a certain way. Outside this scope of possibilities, we tend to feel lost and helpless. If in a laboratory, a high tech machine used for analysis breaks down, how many of you will still know who to tackle the problem in the old fashioned way, down to basics where it all started.

An other good way of filtering substances which may attack cotton wool, is by using Glass wool instead. Glass wool may be obtained in it's fluffy form (like cotton wool), or woven in thin sheets. It's used to fill and strengthen epoxy resins, and is dead cheap. Nowadays, artificial fibre-materials are also used. Carbon fibre, Kevlar fibre, and many more fibre materials which are available in huge amounts anywhere at a very reasonable price. Not those rip-off laboratory prices we are used to dealing with for something that has a different name and intended narrow scope of use. In large scale industrial filtration plants, we often see the use of naturally occurring filtration materials like porous lava stone, pumice stone, diatomaceous earth, quartz sand, sea weed etc.. Many of these filtration materials can be found in fishery and aquarium shops, beer breweries, fruit juice manufacturers, and sewers/wastewater filtration plants.

Regards,

Lambda.

kaviaari - 9-1-2007 at 07:03

This is very very efficent. As long as you'll only need to work with the solution. I have been using this for ages and even though it takes it's time it pays back. One good advice to filterating is also to cut your coffee filter bags to small circles that can be fold like the real stuff. They have worked just fine for me even with vacuum filteration. And as usual I'm adding a link to a picture (dried lithium carbonate, impure) :)

[Edited on 9-1-2007 by kaviaari]

Making a hole through a rubber or cork stopper

Lambda - 9-1-2007 at 07:18

Look for a thin walled metal pipe, made of steal, copper, brass etc. with the right internal diameter. File down the edges of this pipe, so that they become cutting edges. Role this over sandpaper, or a fine file in a circular motion in order to get a sharp cutting edge. This cutting edge may also be slightly cartelled/serrated like a saw, by using a sharp edged file. By using Detergent or Glycerin (water soluble) as lubricant, the sharp edged pipe is pushed through the rubber stopper or Cork by means of a back and forth circular rotating motion. Support the cork or rubber stopper on a sturdy underneath surface, making shore that it can't flip over so that the sharp edged pipe may penetrate the hand. Wrap a few layers of cloth around the exposed part of the hand, or where thick gloves as added protection. For a cork stopper, a low revolution wood spiral drill may also be used. The round drills with a center guidance spike, and the cutting edges on the outer side, work just fine.

Regards,

Lambda.

Side note to the original post

UnintentionalChaos - 9-1-2007 at 11:33

You want, specifically, the Diatomaceous earth for pool filters. There are two varieties of DE, freshwater, and saltwater. Saltwater is mainly used industrially and has a high percentage of crystalline silica, which (aside from being a health hazard for silicosis) does a tremendously better job filtering than the largely amorphous silica in freshwater DE. Pool filter material is either saltwater or heat-treated freshwater DE. The stuff used for cat litter and insecticides is not crystalline, as the absorbent qualities of the material, available in the less hazardous amorphous form, are preferred.

Edit #1: Great tip there, Lambda. It just occured to me why that sounded so familiar. Back in high school I used to use pen tubes to punch holes in those block erasers to entertain myself. :)

Edit #2: Another filtration material that is easily available is polywool, which can be purchased from almost any half-decent craft store as "batting" used for stuffing pillows. Since it is plastic, though, I'd avoid certain solvents. It also makes a great inert material for use in low temperature apparatus design. There was a simple lab in college where it was used to keep KOH and CaSO4 (drierite) in a disposable syringe tube through which a mixture of methane, CO2, and water vapor was lead. The gas, after passing through the tube was dry methane which was used to determine the efficiency of our anaerobic reactors. :)

[Edited on 1-9-07 by UnintentionalChaos]

Where can I find it ?

Lambda - 9-1-2007 at 13:39

An other good place to find the above mentioned filtration materials, are Art and Pottery supply stores. These stores also have a surprising amount of "hard to get" chemicals. Not only do they have dry organic pigment powders, but also inorganic pigments which often contain very pure metal oxides, sulfides, sulfates etc., and also many different acids and solvents. Art shops that deal with bronze making, have Jerrycan loads of Sulfuric acid, Nitric acid, Ammonium Sulfide (yes, that highly toxic stinky stuff), Phosphoric acid etc.. Art shops that deal with pottery, have many different dry inorganic based pigment powders. Even rare metal salts are used and sold for use in pottery glazer and enameling. Heat resistant materials in all forms and shapes, which are at the same time good heat isolators, can be used to heat protect a laboratory work bench. Certain porous materials sold by these shops, again can be used for all kinds of filtering purposes. Fishery shops sell many kinds of filters and filtering materials of interest to the Chemist. Also cheap pH-meters, Conductance-meters, sets and kits for the determination of Nitrates, Nitrites, Sulfates, Chlorides, Oxygen, Carbon dioxide etc. in water. As for the usual color chart pH-paper, all to determine the water quality. Similar measuring kits and devices can also be bought from agricultural stores, as for huge amounts of pure Ammonium nitrate, Calcium Nitrate, Potassium Nitrate, Sodium nitrate, Nitric acid (as high as 60%), sulfuric acid, phosphoric acid, Sulfur (pure powder), Metaldehyd, Paraformaldehyde, Methyl bromide, and a surprising amount of very interesting insecticides. Coloring agents for flowers, apples, oranges, lemons, bananas etc.. The list of "Big Brother" unprotected sources" of chemicals and materials are huge. All you have to know is what chemical or material you are looking for, and it may surprise you to know that you are just sitting on it as you think were to find it.

Regards,

Lambda.

BromicAcid - 9-1-2007 at 16:21

Quote:
An other good way of filtering substances which may attack cotton wool, is by using Glass wool instead. Glass wool may be obtained in it's fluffy form (like cotton wool), or woven in thin sheets. It's used to fill and strengthen epoxy resins, and is dead cheap.


I never really had success finding glass wool outside of lab supply shops so I used fiberglass insulation instead, just wash it with some HCl first, for some reason this noticeably discolors the pink kind I used to get but the yellow stuff is unaffected. I never had any problems with it though, I used it for filtering strong oxidizing solutions such as when I did work with ferrates and such.

alyks - 27-1-2007 at 12:16

Herb shops have Amber bottles.

glass wool

Magpie - 18-4-2007 at 14:39

I recently had need to filter a nitric acid solution. What I wanted was glass wool. The best I had was some building insulation that was white in color, ie, uncolored. It worked beautifully for clearing up the solution. However, I wasn't sure that I hadn't contaminated my solution with any binder material that might have been a part of the insulation.

What is your opinion on whether the white building insulation has a binder or not?

Also: does anyone have any new information on OTC sources of glass wool?

12AX7 - 18-4-2007 at 15:09

Dunno.

Kaowool, which is white and made from aluminosilicate (I forget if it has magnesium), works nicely for me.

Tim

not_important - 18-4-2007 at 16:33

I'll second Kaowool, from pottery supply stores, and the similar if not identical Superwool and "Porcelain Prop". A possible alternative is the "ceramic papers", which are a few mm thick.

Some of the pottery materials have organic coatings that burn off in first use. They may be rather brittle afterwards, and thus may not be the best choice. Sometimes the only way to know is to try using the minimum purchase and see.

You could treat your insulation in a similar fashion. Perhaps a good soak in acetone, a wash with hot xylene, then let it dry and heat it carefully with a torch or hold it over a hot electrical element. Finally wash with water to remove soluble inorganics.

16MillionEyes - 21-4-2007 at 14:10

Would cotton be a good filter for KOH from ash water?

not_important - 21-4-2007 at 16:59

Quote:
Originally posted by __________
Would cotton be a good filter for KOH from ash water?


Cotton tends to swell in strong alkali, but I think that the mostly carbonate extract from ash would be OK.

If you mean cotton wool, I believe that you may find a lot of cotton fibers will wash on through. Plain undyed well washed cotton cloth would work. You may need to filter twice, once with a fairly coarse weave to hold back most of the ashes, and a second time with a finer weave to clean it up.

Levi - 23-4-2007 at 23:26

It might be worthwhile to combine techniques when filtering ash leachate. I know from experience that filter paper does a lousy job of removing organic scum but provided that the cotton was able to do a better job removing the organics, the filter paper should do fine at keeping the cotton fibers out of your solution.

dennisfrancisblewettiii - 24-4-2007 at 04:28

Quote:
Originally posted by Lambda
@UnintentionalChaos, I couldn't agree more with you, and maybe if I may add, @S.C. Wack too. For he has an intense love and interest for chemistry books of Nostalgia, in which all these very basic (and even long forgotten by many) procedures are described.


Nostalgia? Is that a publisher, book series, or something? Or are you being rhetorical? I can't tell...

16MillionEyes - 29-4-2007 at 07:06

If we just bring it down to everyday household materials, it seems then that cotton would do the best job. The problem would be then to get some filter paper. Any ideas?

UnintentionalChaos - 29-4-2007 at 07:26

Coffee filters work decently well and can be cut to fit a buchner if you have one. They are only real good for gravity filtration of fairly large particles. Certain solid reaction products, you will find can pass through them in decent quantities. Real filter paper is not too hard to come by and can be ordered offline if you look for it.

Gravity

MadHatter - 29-4-2007 at 11:46

May I also suggest using a filtration flask with a hand held vacuum pump(auto parts shop).
You could also use a flask setup with a 2-hole stopper. This will greatly decrease filtration
times vs. gravity. BTW, a continous vacuum source, especially aspirators, will cut down
the time enormously. This is particularly useful when making hydrazine because of the gelatine
used to prevent attacks on the hydrazine.


[Edited on 2007/4/29 by MadHatter]

16MillionEyes - 30-4-2007 at 18:07

I've had the opportunity to use vacuum filter. Works decently but unfortunately I don't have one of my own. I guess gravity will have to do. :D