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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: gangst on February 06, 2008, 05:18:57 AM

Title: Error of syringes?
Post by: gangst on February 06, 2008, 05:18:57 AM

Hi,

I'm writing up an investigation and need to calcualte error. I have error values for all my equipmetn except a 2ml, 5ml and 10ml syringe which I used. I cannot find the error anywhere, so shoul I take the error value as half of the smallest unit on the syringe. I.e 0.25ml for the 5ml and 10ml syringes and 0.05ml for teh 2ml syringe?

Thanks for any help.

Title: Re: Error of syringes?
Post by: Arkcon on February 06, 2008, 08:33:11 AM

I'd use the value printed on the syringe, it should be there.  If not, it should be on the box, or package insert, or the catalog you bought it from.  Now, if this is a class, you may not have access to these other printed sources of error, like you would if you've ordered these supplies yourself, but you should ask to see them.  After all, you were asked the question in lab write-up, so it should be answerable. 

I can't say for sure, but I don't think your estimates are valid ways of determining error in the syringe.

Title: Re: Error of syringes?
Post by: enahs on February 06, 2008, 08:40:12 AM

Arkcon is correct. But for a simple high school write up the teacher is probably interested in seeing you know how to calculate the error. So as long as you explain why you chose those values for the syringe, you should be fine. But I would of course ask the teacher first.

Title: Re: Error of syringes?
Post by: Mitch on February 06, 2008, 01:07:43 PM

All syringes need to be calibrated prior to use.

Title: Re: Error of syringes?
Post by: gangst on February 06, 2008, 02:42:01 PM

well its not really high school its for my chemistry A2, i wasn't sure where to post my enquiry.

yes, i have looked at the equipment and the error is not printed on the side unlike burettes etc.

also i have looked for the box, and have had no luck, as well as looking at an online brochure but agin, there was no error values.

this is really annoying, i've been told to take the value as half of the smallest measurable unit on the scale of the syringe,however am not sure if this is correct?


thanks for your help

Title: Re: Error of syringes?
Post by: Arkcon on February 06, 2008, 03:36:47 PM

If the teacher say so, then go ahead.  But like Mitch says, if you want to be correct, you should check them yourself.  Now, I've never done this with a syringe, but I don't use them for accurate volume measurements.  I have checked the calibration of adjustable mechanical pipettes, either by weighing water, or spectroscopically, with a colored standard solution.  I've never checked the calibration of a volumetric flask or pipette, I've always assumed they were accurate.  'Tho I did hear once of a slew of bad results traced back to a bunch of new 15 mL pipettes, that turned out to be 13mL in volume.  :o