Used to have family in the ice business back when the ice boxes were
wood. Was talking
to a relative (he's 80) about how his uncle made the ICE. He said as
best as he could
remember they used big diesel motors attached to big flywheels that ran pumps. 
They pressurized Ammonia and salt water and ran it in pipes around 300
gallon steel
tanks - of water that that would freeze. He said you could really
smell the ammonia
and thought that when the Ammonia is pressurized it got colder.

What type of preasures effect this type of reaction in Ammonia? Simple Charts?

Hello amiteriver, I have a particular fondness for ammonia cycle
refrigeration because I made a good grade on a test in a
thermodynamics course long ago that was an analysis of an ammonia
refrigeration plant. Ammonia was one of the earliest fluids used for
refrigeration:

http://www.nh3tech.org/history.html

Refrigerants used in the early vapor compression machines included
ammonia, sulfuric ether, carbon dioxide, sulfur dioxide, methyl
chloride and some hydrocarbons. In the 1930's and 1940's the
halocarbon refrigerants (commonly known by such trade names as "Freon,
"Genetron," "Isotron," etc.) were developed, giving the industry a
strong push into the household market because of their suitability for
use with small horsepower motors. The past 50 years have seen the
refrigerator move from luxury to necessity. The entire food
distribution chain has become dependent upon refrigeration, from the
farmer to the shipper to the processor to the supermarket to the home.
It is a miracle of modern technology that has been over 300 years in
the making. And playing a large part in the past and the present of
mechanical refrigeration is the industrial refrigerant ammonia.

I think that the salt water your relative remembers was used as a
secondary refrigerant as shown in this diagram:

http://cipco.apogee.net/ces/hctre.asp

They most often use a lithium bromide/water pair but can be designed
with a water/ammonia cycle. The operation of the absorption cycle is
as follows: The solution of refrigerant (usually either water or
ammonia) and absorbent (usually lithium-bromide or water) is heated in
the generator by steam, hot water, hot exhaust gases or a direct fired
burner. This boils off the refrigerant (thereby also creating a
concentrated absorbent) which is then condensed in a condenser
(normally water-cooled). The refrigerant liquid then passes into the
evaporator section which operates at very low pressures such that the
refrigerant boils to provide the required cooling. This low pressure
and vapor generation are maintained by the absorbent concentrate. The
vapor flows into the absorber where it comes into contact with the
strong solution from the generator. This solution is then transferred
back to the generator to complete the cycle.

Here is a very good description of a modern ammonia refrigeration cycle:

http://www.neerenterprises.com/ammonia_compressors.htm

Wide range of refrigeration and air conditioning Ammonia compressors
are offered by Neer Enterprises under the brand name of "KAFCO".

Ammonia compressors designed with state-of-the-art technology for
industrial & commercial refrigeration and low temperature applications
like ice plants, cold storage, fisheries plants, dairy plants, ice
cream plants, chemical plants, pharmaceutical plants and air
conditioning plants.

Here is the best explanation of the ammonia cycle I could find (I hope
you can view .pdf files):

http://web.me.unr.edu/me372/Spring2001/Refrigeration%20Cycles.pdf

I hope that all of this makes sense to you. The principle of phase
changes is a very powerful tool and is the basis for many things that
we take for granted in every day life (such as boiling water). Please
let me know if this does not answer your question or there is
something that you do not understand.

Redhoss

Thanks Much