"Colligative" Properties: On Water Parameter I

[Anonymous]

This is one of a series of threads on water and light parameters. The term colligative is used loosely, and I hope I do not mislead anybody to think that I am going to talk about nothing but osmotic pressure, vapor pressure lowering effect, etc..

Objective: Propose a paradigm about colligative property and illustrate the use of paradigm in the water and light parameters in reef hobby.

Purpose: Describe several water and light parameters used in the reef hobby in layman term. More advanced discussion (detailed specifications, advanced math. formula and other more technical issues) will be posted in the General Reef Forum if interest is sufficient.

Since I don't have time to complete all the discussion in one setting, I had requested that this thread be locked. I will added additional post to the thread as time permits. I apologize for any inconvenience. I also want to apologize for my grammar and spelling mistakes.

 

[Anonymous]

There are many dissolved chemicals and suspended materials in saltwater. It is very difficult to describe all of them so a specific attribute is used.

If we take every aspect of saltwater as a color on a particular pixel, then a full description of the saltwater will be a picture, such as this:

So it is like assigning a specific value to a picture, say 0.034.

Obviously, the value has some special, rational significances and physical meanings, but I would like to point out that the value does not fully describes the picture, and several distinct pictures may have the same identical value.

The following is a list of topic that I will describe with that paradigm: specific gravity (SG), density of saltwater (density), total dissolved solide (TDS), Conductivity, Resistivity, reverse osmosis rejection rate.

 

[Anonymous]

The density of salt water is one of the simpliest parameters to understand. It is just the weight of the saltwater in a specific volume. In particular, if it is the weight of water (gram) in one milliliter of volume, then the unit will be in g/ml. Other common unit is g/cc (cc = cubic centimeter).

The density of water changes as temperature changes. For example, water is most dense at around 4 C (~39F), while it is less dense at higher and lower temperature. For this hobby, we don't need to worry about the case for water between 4C and the freezing point.

At aquarium temperature, the density of water is less than 1 g/ml, but with the addition of significant amount of salt, the density of saltwater is much higher.

(I will continue this when I come back later )