Hi Bob,

for the capillary from the acid reservoir to the pump and the pump head 
itself: put everything in hot water. The water will dissolve the acid 
crystals. You can also replace the steel capillary from the reservoir to 
the pump in case it is clogged (not so expensive; or try the procedure 
described below for the acid needle).

For the acid needle (quite expensive) we used the following:
We filled hot water into a sample vial and closed the vial with a septa 
cap. We gently forced the end of the capillary which is connected to the 
pump through the septa into the water (not the end with the needle; but 
the needle end may also work). I also pushed a needle from a disposable 
syringe through the septa and connected this needle to a compressed air 
outlet. We just pressed the plastic end of the needle and the airgun 
together but you can also try to build a more sophisticated connection 
with some Swagelok parts from your drawer. The air pressure in the vial 
will force the water into the capillary and the acid out of the needle 
at the other end. This can take a few minutes, so be patient. To 
visualize the flow of acid out of the needle tip we put the needle into 
a second vial filled with water. You can see the acid coming out as a 
thin "band".

I never thought about the high pressure in the vial and if this can 
cause a burst of the vial...so you better make sure to wear some safety 
goggles and do things in a fume hood with a pane.

When the pump is out out of work for a few weeks or even months make 
sure to flush everything with water before you switch of the pump. For a 
re-start pump (1) water than (2) dissolved phosphoric acid (which less 
viscous (about 85%, we just mixed the real stuff with some water), and 
finally the (3) real viscous acid (thank to Gerry for this tip!). We 
also experimented with a heating band around the pump head but this was 
not a real enhancement. In case the pump is not used for a few days make 
sure to run the pump manually regularly (at least twice a week)

At this point make also sure to remove or replace the rubber septa on 
top of the acid reservoir if there is still one. The rubber starts to 
decompose by the acid vapor and little pieces can drop into your acid 
and can be transfered into the pump head (quite a mess...).

hope this helps,
Robert

-- 
Dr. Robert van Geldern
Section 3: Geochronology and Isotope Hydrology
Leibniz Institute for Applied Geosciences (GGA-Institute)

GEOZENTRUM HANNOVER
Stilleweg 2
30655 Hannover, Germany

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