Trailer: The National Bureau of Standards of the United States Department of Commerce has been examining the characteristics of carbon dioxide. It is well known that when a liquid has its surrounding temperature raised, more gaseous molecules are formed. The National Bureau of Standards study was looking at the effects of raising the temperature of a cell of liquid carbon dioxide and how its density will be affected. At 31 degrees Celsius, the critical point is reached. The critical point is where the density of liquid molecules and gaseous molecules is equal. The Bureau uses three balls to monitor how the density changes during the heat up and the cool down. There is actually a phenomenon that occurs in the carbon dioxide during the cool down, in which the carbon dioxide begins to look opaque. See the full length at: www.qualityinformation.com