[nelson]

THanks a lot WM6, i will look forward for information related to the subject we are concerning about.
Regards
Nelson

Originally Posted by WM6

Hi Nelson

So called Tyndall effect was used here. Tyndall effect was widely used to detect existence and concentration of silver and gold nano-particles in solutions but can be used in air too. To establish Tyndall effect we use laser of different colour spectrum, depending of particle size which can be from ions to some nm. Green light laser pointer are most powerful but not suitable to all nano-particles diameter and all metals. Red light laser pointer are suitable in general. So, the best solution would be fitting more laser pointer of different light spectrum stocked at device. Sensors and electronic remain unchangeable. With this device we are looking for flocks of ions over soil after sunset, not at the sunlight.

You can read more about Tyndall effect on web e.g. here:

http://www.silvermedicine.org/colloidal-silver-ppm.html
or here
http://www.scienceinschool.org/print/656

And here citation from site: http://mysite.du.edu/~jcalvert/phys/colloid.htm:
Sols that contain inorganic particles, such as metals, are mostly lyophobic, as are most aerosols and solid sols. Lyophobic hydrosols are a very common kind of colloid, and deserve detailed description. For example, consider the hydrosol of gold with particles about 4 nm in size. This was one of the first sols studied extensively, and has interesting properties. With about 0.1% gold, the sol is a rich ruby red. The similar solid sol in glass makes ruby glass. The gold particles absorb strongly in the green and blue, so the transmitted light is red. There is a little yellow-green scattered light, but mostly it is a case of absorption by the gold metal. If the gold particles clump together, which they may do as time passes, the color of the solution changes. When the particles are about 40 nm in diameter, the solution is blue, with considerable scattered light. If the particles agglomerate further, the color disappears and gold flakes settle out.