Let me say that nearly all ...

Let me say that nearly all comments are correct except the coefficient in TDS = 0.64*EC is not true. Depending on the character of the water it may vary from 0.55 to 0.75. Here are referencesa to key works on this topic.

Hem, J.D., 1989. Study and Interpretation of the Chemical Characteristics of Natural Water, U.G. Geological Survey, Water Supply Paper 2254

This supercedes

Hem, J.D., 1970. Study and Interpretation of the Chemical Characteristics of Natural Water, 2nd Ed, U.S. Geol. Survey, WSP 1473

also

Garrels, R.M. 1960. Mineral Equilibria at Low Temperature andf Pressure, Harper & Brothers, New York.

and Garrels, R.M. and Christ, C., 1965. Minerals and Equilibria.

The bible of water chemistry is

Stumm, W. and Morgan, J. 1981, 2nd Ed.. Aquatic Chemistry, An Introduction Emphasizing Chemical Equilibria in Natural Waters, John Wiley and Sons, Inc., New York

Also you might enjoy this fun book

Barth, R.B., 2010. The Chemistry of Beer, 2nd Ed. Greene Publications, West Chester, Pennsylvania.

Regarding to TDS it is generally taken to mean dissolved natural solutes and should not include miscible organic compounds that may show up when the water of a sample is completely evaporated.

Garrels