>I am using a Carlo Erba NA1500 and have found that the translucent
>silica tube can be cooled and reused but that the clear transparent
>silica fractures on cooling. Care must be taken with the translucent
>tubes as the end tend to chip and then a good seal is hard to achieve.

On our Europa ANCA NT S/L unit, I have just the oposite experience.  The
translucent tubes are used for combustion at 1000 C, while the transparent are
used for reduction at 550 C.  I can pull out the transparent and just let it
cool with no problems, but I have never been able to pull out a translucent and
have it not crack.  I've tried lowering the furnace temperature in stages also,
but that doesn't seem to work.  Any suggestions or tips on saving translucent
quartz tubes from destruction would be greatly appreciated!

myq

-- ----------+-------------------------+------------------+
| Myq Larson | Stable Isotope Analysis | [log in to unmask]   |
|            | Utah State University   | 435.755.6753 (h) |
| Knowledge  | 5305 University Blvd    | 435.797.0060 (w) |
| Liberates  | Logan  UT  84322-5305   | 435.797.1575 (f) |
+------------+-------------------------+------------------+