 Units
Date:2013-07-31

Length: 1 m = 106 &micro;m = 109 nm = 1010 &Aring;

Volume:
●   Cubic Meter (cube of 1m side)  = 1 m3
&#61550;  ■   1 m3  = 1,000 dm3 (cubic decimeter) = 1,000,000 cm3 (cubic centimeter) = 1,000,000,000 mm3 (cubic millimeter)
●   Liter : 1 L = 1 dm3
&#61550;  ■   1 L = 10 dL (deciliter) = 100 cL (centiliter) = 1,000 mL (milliliter) = 1,000 cm3 = 1,000,000 &micro;L (microliter).
E.g. The volume of a drop is about 50 &micro;L.

Weight:
Kilogram (kg):
&#61550;  ■  1 kg = 1,000 g (grams) = 1,000,000 mg (milligram) = 1,000,000,000 &micro;g (microgram).
●   Ton : 1 Ton = 1,000 kg
●   Water density : dwater = 1═> 1 L = 1 kg

Concentration:
&#61550;  ■   ppm = 1 part per million (= 1/1,000,000)
&#61550;  ■   ppb =  1 part per billion  (= 1/1,000,000,000)
&#61550;  ■   ppt = 1 part per trillion  (= 1/1,000,000,000,000)
&#61550;  ■   ppq = 1 part per quadrillion (1/1,000,000,000,000,000)

On a weight scale :
&#61557;        ◆  1 ppm = 1mg / kg
&#61557;        ◆  1 ppb = 1 &micro;g / kg
&#61557;        ◆  1 ppt = 1 ng / kg

On a time scale :
&#61557;       ◆  1 ppm = 1 second per 11.5 days
&#61557;       ◆  1 ppb = 1 second per 32 years
&#61557;       ◆  1 ppt =1 second per 320 centuries