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#1
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accurate scales
Larry wrote:
hello all, I am looking for a scale which measures up to .001 grams accuracy (. 0001) but is inexpensive (not cheap). I only need to measure up to 50 grams at that accuracy. Does anyone know where I could find such a scale? (Preferably in Canada, BC to be more exact) For darkroom work, or even drug dealing, I cannot imagine needing such accuracy. The chemicals you buy, even photo grade, are not that pure, nor do they need to be. I use an Ohaus triple beam balance that is good to 0.1 grams up to about 600 grams, and that is good enough. Your exposures are not that accurate. Your apertures are not that accurate. Your developing times are not that accurate. Your solution temperatures are not that accurate. Film speeds are accurate to only about 1/6 of a stop. If it is simply a matter of measuring a small amount of something, make a 1% solution of whatever it is and use only a few millilitres of it. Were I mixing a litre of some solution that needed only 0.001 gram of something, I bet the solution would work the same without it. -- .~. Jean-David Beyer Registered Linux User 85642. /V\ PGP-Key: 9A2FC99A Registered Machine 241939. /( )\ Shrewsbury, New Jersey http://counter.li.org ^^-^^ 08:05:01 up 23:56, 3 users, load average: 4.34, 4.30, 4.12 |
#2
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accurate scales
Jean-David Beyer wrote:
If it is simply a matter of measuring a small amount of something, make a 1% solution of whatever it is and use only a few millilitres of it. Very good point. And I will add that dissolving something to make a solution is important. If a chemist says 'stir', he means it. Don't shake: stir. (I wonder if everyone got the feeling I did when first mixing Rodinal 1:200. "Is it really in there?" Now I just drop it into the water and it incorporates within a minute.) Were I mixing a litre of some solution that needed only 0.001 gram of something, I bet the solution would work the same without it. Ah, but you aren't making nerve poison! |
#3
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accurate scales
Larry wrote:
I am making a one gram batch of Kodalk which calls for .692 grams borax and .145 grams NaOH. I realize that the ingredients are not that pure so there is a margin of error. This recipe does not allow for such deviation otherwise I'd be measuring out .69 grams and .15 grams or less.... Understood now. So make ten grams. |
#4
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accurate scales
"Larry" wrote in message ... On Jan 22, 6:35 am, John J wrote: Jean-David Beyer wrote: If it is simply a matter of measuring a small amount of something, make a 1% solution of whatever it is and use only a few millilitres of it. Very good point. And I will add that dissolving something to make a solution is important. If a chemist says 'stir', he means it. Don't shake: stir. (I wonder if everyone got the feeling I did when first mixing Rodinal 1:200. "Is it really in there?" Now I just drop it into the water and it incorporates within a minute.) Were I mixing a litre of some solution that needed only 0.001 gram of something, I bet the solution would work the same without it. Ah, but you aren't making nerve poison! I am making a one gram batch of Kodalk which calls for .692 grams borax and .145 grams NaOH. I realize that the ingredients are not that pure so there is a margin of error. This recipe does not allow for such deviation otherwise I'd be measuring out .69 grams and .15 grams or less.... The formula above is for the equivalent of sodium metaborate in solution. You can always mix a concentrated solution and measure off the equivalent of one gram. That would allow the use of less precise scales and the accuracy and precision of the liquid measure would not have to be so fine. I wonder what exactly you are trying to do. -- -- Richard Knoppow Los Angeles, CA, USA |
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