Liquid Nitogen rate of loss

Does anyone know what the rate of loss for liquid nitrogen is?
The reason for asking is I'm wondering if my supplier stiffed me. I
had a 160L delivered for the first time. After using no more than 60L
in 25-30 day period, it was all gone. The gauge on this tank did not
work, and there is no way for me to know if it was filled all the way.
By the way, I paid approx. $135 including delivery and the tank rent.
Is this reasonable? Any suppliers you know in California?

thanks for your help,
Nick

[Only registered users see links. ] (Mike M.) wrote in message news:<633d25aa.0401032236.65240d76@posting.google. com>...

Seems totally reasonable to me. A month is a long time to keep
a tank around, and still have much liquid left at all.
Your price including delivery and rental seems like a
pretty good deal from here. Mighta been nice if the gauge worked.

Cheers,
Tony

Dear Mike M.:

"Mike M." <[Only registered users see links. ]> wrote in message
news:633d25aa.0401032236.65240d76@posting.google.c om...

Nitrogen evaporation will be a function of how much heat it absorbs from
the environment. This will be expressed as both time, insulation quality,
and environment. The time you had it was really long, which will let a lot
evaporate. California has been pretty warm, and you may have kept this
container indoors, and humid air also contains more heat capacity, so these
will all add to the evaporation rate.

I think your supplier did not short you. You may want to look at how much
you buy (and how often), and where you keep it.

David A. Smith

N:dlzc D:aol T:com (dlzc) wrote:


A good check is to put the dewar on a scale. You need to know the empty
weight, but your supplier should be able to tell you or just wait till
it is empty. Sitting it on a scale lets you know exactly how much you
have left.

josh halpern

Josh Halpern <[Only registered users see links. ]> writes:

I don't know whether this is feasible for a dewer or not, but I have
read where you can determine the depth of gas in an ordinary metal LPG
cylinder by splashing some hot water on the side of the cylinder. As
the water dries up (evaporates), it first does so off the warmer part,
which is where there is vapour rather than a cooling/evaporative liquid
on the other side. While the difference in temperature will be powers of
ten less marked in a dewer, it might still be enough to show a distinct
line at the liquid/vapour interface. I'm not near a lab at the moment so
I can't test it.
--
John Savage (news address invalid; keep news replies in newsgroup)

John Savage wrote:


Tends not to because the Dewar is better insultated, What you can do is
take a tube and stretch (your choice) either a latex glove or a condom
(unlubricated) over the top. You put your finger on (not in) the rubber
and insert into the Dewar untill you feel it start to vibrate. That is
the depth at which the liquid is.

josh halpern