Doug,

The way I used to do this was by simple comparison with a hellishly
expensive standard hydrometer, with a standards certified calibration
certificate, kept in a beautifully polished mahogany box. If I remember
correctly, it had a range of 0.850 to 0.875 at 20°C, with another one
for 50% solution 0.900 to 0.925. They were about 50-60 cm long and had
calibration marks at 0.001 intervals. Of course, if you wish to go to
basics, weighing an SG bottle at a carefully controlled temperature is
the best way, if you have an analytical balance with certified weights.

Hope all is well with you.

Brian

Douglas Pauls wrote:
>
> Good morning all,
>
> In a recent ISO audit, an issue came up here regarding calibration of the
> hydrometers we use.  These instruments are normally used to determine the
> percentage of isopropanol in a 75%/25% IPA/Water solution.  The nominal range
> is 0.82 - 0.89.
>
> Do any of you know of any calibration services out there which will calibrate
> hydrometers in this range?  If so, could you provide me a contact?
>
> Thanks.
>
> Doug Pauls
> CSL
>
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