On Wed, 23 Jun 2004 02:22:43 +0200, Trevor
wrote:

On Tue, 22 Jun 2004 18:06:07 -0400, NetMax wrote:



If you can figure out a reliable conversion, please share it. I've read
that for salt calculations, because of water's changing density, the
calculation should include temperature, with the reference typically being
59F. The few times I've tried to calculate salt dosages (with patient
help from others), we came out to approximately 1g = 1ml and a tablespoon
per g was 0.3%. While this might not be very accurate, 1 tsp/g = 0.1%
helps me be consistent.

I think that your estimates are probably well good enough for most
applications. I think people overestimating the exact amount of water
would be more of a problem in getting the right concentration. In my 3
foot tank I was amazed at how much the water level dropped when I took all
the rock work out. Then there is also the volume of tank taken up by the
air space between the water level an the top of the glass.

Doesn't temperature only come into play when you are measuring the
specific gravity with a hydrometer above or below the 60F (at which temp
plain water has an sg of 1.000 The particular hydrometer I am using I had
left over from beer making. Incidentally it seemed to show only slightly
above 1.000 but below 1.001 for my estimated 0.1 % solution (at 25C) I am
not sure what reading I should have expected. I figure it is not accurate
enough to be reliable used at such low concentrations. I also did not
consult a temperature correction table.

How does one relate the SG to a percentage solution? (at 60F of course !)

On googling I see that once can buy a hydrometer calibrated to show the %
salt solution.


I think that consistency _is_ the key here. You will soon get a feel for
if your concentration is too strong (fish adversely affected immediately
or over a long time) or too week (not curing the problem for which it was
applied) or having no noticeable beneficial effect over a long period when
you would normally expect it too.

I should add YMMV here as I am no expert and this is my first time using
salt.

Trev

PS I am



Some more reading:

http://www.advancedaquarist.com/issu.../chemistry.htm

Unfortunately it is geared to seawater concentrations.
If we take 100 grams of water and add 1 gram of salt, we would have a
1% solution. We are doing this at the temperature where 1 cc of water
weighs 1 gram, whatever that is.

Assuming the solution doesn't change volume (it could increase,
decrease, or remain the same)we would have 100 cc that weigh 101
grams.

101/100 = 1.01 specific gravity.

Another way to figure is 99 grams of water and 1 gram of salt to get
100 grams of solution.

100/99 = 1.01010101...

So 1.001 for 0.1% sounds right, ignoring all the variables that are
too small for us to measure anyway.


--

- Charles
-
-does not play well with others