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Author: Subject: New High School Teacher looking to outfit a classroom
Saerynide
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[*] posted on 14-12-2008 at 11:45


For the American Weigh scales, Ive tried both:
American Weigh DIA-10 Digital Carat Scale 50x0.01ct / Milligram: http://www.americanweigh.com/product_info.php?cPath=60&p...

and

American Weigh Gemini-20 Portable Milligram Scale 20x0.001g: http://www.americanweigh.com/product_info.php?cPath=60&p...

For My Weigh, Ive tried My-weigh GemPro50 Jewelry Scale: http://balance.balances.com/scales/870

All 3 times, I had to send them back to the seller. Maybe their larger capacity scales will be more accurate and precise, but I can vouch for sure to stay away from their mini scales - they have no accuracy or precision.

Several times, I've tried putting 3-4 mg of material on them and they will often register nothing. The American Weigh ones were so ridiculous as to measure the calibration weight wrong every time even after calibration (I had previously measured the weight in my research lab to the 0.1 mg, so I know what it *should* weigh).




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Stifle
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[*] posted on 15-12-2008 at 12:53


that sounds pretty bad. accuracy would be top of the list on my priorities for these scales so I guess ill have to find some other brands to use.
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zed
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[*] posted on 15-12-2008 at 15:36


Burets appear to be overpriced. Want to do some titrations? Use disposable syringes.

They are graduated, easy to control, hard to damage, and are very inexpensive. If you are concerned about the pointy ends of the needles, just cut them off.

Syringes work equally well, as graduated cylinders.

Burets and other chemical glassware/plasticware are specialty items. Naturally spendy.

Disposable syringes are not specialty items, they are produced in all sizes, on a vast scale. Diabetic supply companies/clubs sell them dirt cheap.
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Lambda-Eyde
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[*] posted on 16-12-2008 at 00:58


Zed: I think a school easliy can afford burets, and IMO they are superior to plastic syringes when it comes to titrations. There's a reason professional labs don't use syringes, you know. ;)
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undead_alchemist
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[*] posted on 16-12-2008 at 11:53


The company that I work for has pretty good prices on both ASTM Class A, and ISO DIN Class B Burettes.

How about a micro scale 1ml, 2ml or 5ml Class B??..
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zed
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[*] posted on 17-12-2008 at 01:48


No point in spending big bucks on burets for a high school chem class. Cheaper is better.
Ideas are the important thing, not pin-point accuracy.

My experience with burets at the college level was that they were extremely mortal. They are long, awkward, and fragile. Easy to break and expensive to replace. Students would break them, then be aghast at having to pay the high replacement cost. The presence of a stopcock sends the price soaring.

In simpler times, to keep costs down, many schools used burets that had a nipple at the bottom end. Slip a piece of latex tubing over the nipple, stick a tightly fitting glass bead inside the latex tubing, then insert a piece of finely pointed glass tubing at the bottom.

Squeezing at the bead, buckles the latex tubing and allows liquid to flow. Stop squeezing, and the tubing snaps tight again. Just as accurate as a stopcock, at a vastly lower price.

[Edited on 17-12-2008 by zed]
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dapper
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[*] posted on 17-12-2008 at 08:01


oldwillknott.com for scales - great prices, fast shipping
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nitric
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[*] posted on 26-12-2008 at 02:51


as for heating if you would be allowed(lack of natural gas lines) use propane tanks, easily you could set up them and they would be refillable, even though electric is good for most applications in a lab, it would at least be on hand if Bunsen burners were needed
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[*] posted on 20-1-2009 at 12:39


I am selling some Jones reagent- great for visual aid for changes in oxidation states Cr(VI) red to Cr(III) green
see ebay item 190281558976
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