Calibration of Glassware and Liquid in Glass Thermometers

[Marc]

--> Date: Fri, 29 Jan 1999 20:
-->
--> David S Smith wrote:
-->
--> Hi Marc, I enjoyed reading your comments on several calibration
--> issues. I would like any information concerning verifying,
--> calibrating, whatever glassware; for instance a saccharometer,
--> burets. I have been trying to keep checks using weight
--> comparison,(1grm = 1ml distilled water), but this is difficult w/
--> the 15ml Sacc. Any suggestions.
-->
--> Thanks,
--> David Smith

Dave:

I really don't have any experience with glassware. We'll see if anyone here on the forum has any expddrience in glassware.

[Marc]

For those of you who might be interested - I was....

----------snippo----------

From: "David Smith"
Date: Mon, 22 Mar 1999 13:29:20 -0500
Subject: Calibrate/verify glassware

Hi Greg,
Can you provide me with some tips or suggestions on calibrating / verifying burets, sacchrometers,etc.? How do I decide if it is necessary? When the test points can't be altered due to being etched in place, is a calibration check necessary? I have been trying to keep a check using weight comparison; 1grm = 1ml distilled water. This is difficult to justify accuracy. I am puzzeled with this, give me a suggestion if you can, thanks

Sincerly,
David Smith

----------response----------

Subject: Calibrate/verify glassware
Date: Tue, 23 Mar 1999 09:40:16 -0500 (EST)

Moderator Note,

NIST publication NUST/SP-819 "A Procedure for the Effective Recalibration of Liquid-in-Glass Thermometers" states that high quality liquid-in-glass thermometers require only one complete calibration in their lietime. It is possible to avoid the usual requirement for complete recalibration of the instrument by recalibration of a SINGLE previously calibrated temperature. The need to recalibrate is due to the gradual relaxation of residual mechanical strains in the glass that have significant effect on the volume of the bulb. Recalibration of a SINGLE point provides reliable indication of the effect of this change in volume and provides a means for the accurate adjustment of the remainder of the scale. This is how to deal with thermometers. I would think that other glassware would exibit similar strains. Greg

[Marc]

Saw this later...

-----snippo-----

Subject: Liquid in Glass Thermometers, NATA position
Date: Thu, 25 Mar 1999 09:57:52 -0500 (EST)

Date: Wed, 24 Mar 1999 08:32:46 +0800
From: "Carman, Herbert" - health.wa.gov.au
Subject: RE: Calibrate/verify glassware

Liquid in glass thermometers can be checked for changes in the bulb volume over time by a single ice point check. The ice point check is suitable for checking change in the glass elasticity over time. The scale calibration is used to check the scale has been etched onto the glass in the proper place and should not change. Any change in ice point should be linear over the scale. NATA (Australia) require complete calibration of reference thermometers every 10 years and ice point checks every 6 months.

-----Original Message-----

Sent: Tuesday, March 23, 1999 10:40 PM
Subject: Calibrate/verify glassware

Moderator Note,

NIST publication NUST/SP-819 "A Procedure for the Effective Recalibration of Liquid-in-Glass Thermometers" states that high quality liquid-in-glass thermometers require only one complete calibration in their lietime. It is possible to avoid the usual requirement for complete recalibration of the instrument by recalibration of a SINGLE previously calibrated temperature. The need to recalibrate is due to the gradual relaxation of residual mechanical strains in the glass that have significant effect on the volume of the bulb. Recalibration of a SINGLE point provides reliable indication of the effect of this change in volume and provides a means for the accurate adjustment of the remainder of the scale. This is how to deal with thermometers. I would think that other glassware would exibit similar strains.

Greg

-----The REAL Original Message-----

--> From: "David Smith"

Date: Mon,
--> 22 Mar 1999 13:29:20 -0500 Subject: Calibrate/verify glassware
-->
--> Hi Greg, Can you provide me with some tips or suggestions on
--> calibrating / verifying burets, sacchrometers,etc.? How do I decide
--> if it is necessary? When the test points can't be altered due to
--> being etched in place, is a calibration check necessary? I have been
--> trying to keep a check using weight comparison; 1grm = 1ml distilled
--> water. This is difficult to justify accuracy. I am puzzeled with
--> this, give me a suggestion if you can, thanks Sincerly, David
--> Smith...