Hydrometer Calibration

Hi All,

A company I am working with is using Sodium Bicarbonate in their water and using a twaddle hydrometer to measure the density. During our last Primus inspection they were told to list calibration procedures for the twaddle hydrometer. Unfortunately the only information I have is a chart somebody made with the solution temperature, twaddle hydrometer stem reading, and the % of the Sodium Bicarbonate. I dont know where the list came from but I believe this is what they based their SOPs off of. Would it be safe to say that calibration could be conducted by testing against the chart? 

I am sort of at a loss here.

You can check it in water.  I think the auditor was referencing you to "verify" the hydrometer is still accurate.  You can't really calibrate a conventional hydrometer.

https://camblab.info...ity-hydrometer/

The Twaddle scale is a simplified scale based on specific gravity where 0° Twaddle equates to SG60/60°F of 1.00 (that of water) and each degree Twaddle equals 0.005° SG.