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| You want a digital scale for What?? |
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| jmh:
I got one from eBay of the type you see on 'police camera action' type programmes to weigh gemstones, but the only use it sees these days is to weigh the occasional letter and to weigh our hamsters! |
| jogri:
--- Quote from: ace1903 on September 18, 2020, 06:50:13 am ---Could you please provide info what is used to titrate NaOH? I already have set of lab glassware and maybe 30 chemicals. --- End quote --- The standard approach would be to use muriatic acid with a known concentration, but since you probably don't have that you have to make a primary standard: That's a solution with a known concentration, made by dissolving a substance that isn't hygroscopic (and therefore has a known density and molecular weight)->if you weigh the amount of substance that you dissolved in x litres of water you can calculate the precise concentration of your solution. You then use this primary standard to titrate your NaOH solution. You could use almost every pure chemical that is stable in air, doesn't have an unknown amount of crystal water and that forms an acid when you toss it in water, but the two substances that get used in chemistry labs for this job are potassium hydrogen phthalate (KHP) and oxalic acid dihydrate. Use phenolphthalein as the indicator, and make sure that you will use between 10-30ml of acid for your titration if you want precise results (you can always dilute your NaOH but the primary standards don't have a great solubility in water so you can't make a really concentrated solution). Here is a paper that describes the process, just PM me if you have further questions: https://silo.tips/download/chemistry-111-laboratory-experiment-8-stoichiometry-in-solution-standardization I personally wouldn't go this far just for a film developer as it will probably work just as good even with a +/- 10% deviation in the NaOH concentration, but a titration is a great exercise in precise lab work. |
| tom66:
My father had one of these to weigh jewelry. He was a gemologist though. |
| magic:
--- Quote from: edy on August 13, 2020, 03:30:50 pm ---I read through the entire thread but didn't seem to find anyone questioning the accuracy of these scales. 1. What method do they use to measure weight? 2. How well are they calibrated? 3. Has anyone independently checked how accurate they are? 4. Does weight differ depending on where on the scale it is placed? 5. How will repeated use/battery levels, etc... change the sensitivity/accuracy over time? It is interesting to have a tiny scale (maybe more useful to have the 500g version although not as portable, https://www.ebay.com.au/itm/Portable-500g-x-0-01g-Mini-Digital-Scale-Jewelry-Pocket-Balance-Weight-Gram/223652841494)... ....but in as much as these ARE MEASUREMENT DEVICES, the only thing that matters to me is that they actually do the job accurately, consistently and do not drift over time. Has anyone bothered to check or test this out yet? Besides drug use, they can be used to measure out quantities of gunpowder and other materials for use in reloading ammunitions: --- End quote --- You are going to love this thread: https://www.eevblog.com/forum/dodgy-technology/i-cracked-the-mystery-of-chinese-precision-jewelry-scales/ I don't recommend using Chinese junk for dosing drugs :P |
| coppice:
--- Quote from: pairfkup on June 14, 2022, 08:39:04 pm ---Why are electronic scales considered the most convenient ? --- End quote --- They are clearly the most convenient, giving a quick numerical readout. However, I think they are mostly attractive because they just work so well. Try putting a kilo of something on several models of electronic scale that cost just a few dollars each and the spread of measurements is usually just 3 or 4 grams, and stays like that for a few years. |
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