[pure-silver] Re: Basic Chemistry
- From: "Nicholas O. Lindan" <nolindan@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 13 Jun 2008 06:45:56 -0500
"Laurence Cuffe" <cuffe@xxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
I'd point out that the time to reach the given temperature is,
in principle, infinite!
Not just in principle but in practice. Negligent of
me not to point it out. The reference to high-school
chemistry put me in mind of frictionless motion and
zero air resistance.
The formula works at giving a good starting point when mixing up
stock to produce a working solution of the desired
temperature.
But if there is a barrier of any substance between the two
liquids it won't work for love or money.
I'd use higher or lower temperatures than described and
monitor the temperature of my target solution until it got there.
Ditto. You need to keep both liquids in motion and realize
there will be some overshoot after you pull the bottle from the
water bath. Fill a sink with hot water, put in the liquid
container with a stirring rod thermometer. Swish the bottle
around in the sink while stirring. Notice how fast the temperature
is rising and pull it 5-10 seconds before it hits the final
temperature.
The closer the temperature inside the bottle and the temperature
outside the bottle the longer you have to wait. It's the
temperature difference that drives the heat from the water bath,
through the glass to the liquid inside. From that you can see
why it would take forever.
And don't forget the microwave. For a 1 liter jug you can
figure a seconds per degree figure. Most microwaves have a 1-3
second delay before they start to heat. To calibrate have
two 1 litre jugs at ambient room temperature. Heat jug A for
10 seconds and jug B for 20 seconds.
Seconds/degree = 10 / (temperature jug B - temperature jug A)
Delay time = 20 - (temperature rise Jug B * (seconds/degree))
Time to heat = (desired temperature rise * seconds/degree) + delay time
Things will change with different jugs. Styrofoam will be the
best choice.
its much easier to get water a lot higher than your target
temperature than to get it a lot lower. One other trick,
if you want to speed things up use a reseal-able plastic
bag to hold your solution
For cooling the plastic bag trick works well the other way: fill
the bag with ice and salt and put it in the solution to be cooled;
stir. The salt keeps the melted water in the bag below 32F so
the bag is colder. They sell a thing called a 'cold finger' for
this purpose - picture a large hollow aluminum dildo that you fill
with salt and ice and use to stir the liquid.
==
Nicholas O. Lindan
Cleveland Engineering Design, LLC
Cleveland, Ohio 44121
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