From: "Richard F.L.R. Snashall" 
To:  atm{at}shore.net
Reply-To: "Richard F.L.R. Snashall" 




Aplanatic{at}aol.com wrote:
> Rick,
>
> Try looking up Abbe Refractometer.  This will give you some idea of the
method.  Are you joking about the precision?
>
> -Dave-
>

 From the Schott catalog:

   "with an accuracy of +/-5E-6 with good internal transmission"

I guess that doesn't make it quite 1 part in 10 million, but it does make
it one part in 300000 (5E-6/1500000E-6, my brain slipped a decimal... again
;-).  The dispersion can be determined to 2E-6, though.

                Rick S.

>
>>OK, fine.  Now, will someone explain to me how Schott and
>>Ohara to this to better than 1 part in 10 million?
>
>
>

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