How much HF required to degrade Quartz tube?

[jamesd]

I have a 4.0mm Quartz tube with a internal diameter of 1.8mm.

If I pump hydrofluoric acid (HF) through it, how long will it take to degrade/fail/break?

What concentration HF will be required?

What can I expect?

[oz93666]

This is a fairly small ID , with a relatively thick wall , so I would expect it to last a long time ... Depending on rate of flow of fluid and temperature ...

Not clear if this is a liquid , hydrofluoric acid (HF dissolved in water) , or just the HF gas you are using ?

[jamesd]

Liquid is being used, 5mL of HF (48%) in 100mL H2O.
It is set up to pump through the tube with a peristaltic pump at 10rpm.
Room temperature 20-25C.

Found that I lost approx 1% weight after 24 hours.

[oz93666]

Am I reading that correctly?? 5ml of HF gas (48%pure) in 100ml water? ... that's very weak ....

so total mass of HF is 2,5ml x dencity = about 1 mgm

Even if all the gas reacted , weight lost should only be around a milligram .... one thousandth of a gram

[jamesd]

5mL of HF liquid made up to 100mL with water. pH approx 1.5

Is there an equation to calculate rate of dissolution?

[oz93666]

Originally Posted by jamesd 5mL of HF liquid made up to 100mL with water. pH approx 1.5 Is there an equation to calculate rate of dissolution?

Pure HF can be liquid , boils at 19C ... but you must mean 5ml of HF dissolved in water since your pH is too low ...

1.5 pH is much less than 1% HF in water ... see the pH graph in this link http://www3.imperial.ac.uk/pls/porta.../1/7276108.PDF

To be more accurate I need to know what this 5ml is ?? did it come from a bottle or pressurized cylinder?

[jamesd]

5mL came from a bottle; such as on this link:
http://www.merckmillipore.com/AU/en/...ogle.com.au%2F

[oz93666]

Ok ... that's hydroflouric acid (HF in water) .... 5ml will contain about 2 gms of HF ..if all the HF reacts (very unlikely) if should dissolve about 2 gms of glass ..

but put in 100ml of water your pH should be much higher than 1.5 ...see the link ..

The acid may have reacted with your pH meter.