Model M Manual : Appendix

 

 

Carbon Dioxide Information (CO2)

Carbon dioxide is a nonflammable, colorless, odorless, slightly acid gas. It is one and one-half times as heavy as air. CO2 is used in the carbonation of soda pop, as an inert agent in fire extinguishers, in canned food products, and many other applications.

 

Below 88°F, confined CO2 liquid and gas are in equilibrium at a vapor pressure shown in the table below. For example, a container of CO2 liquid and gas at 59°F has a pressure of 723-psia. As gas is removed from the cylinder, the liquid vaporizes into a gas, which maintains the vapor pressure shown. When all of the liquid has been vaporized, the gas pressure will reduce as gas is withdrawn. Following is a table of the vapor pressure as a function of temperature.

 

Temperature			Pressure
°F	°C		PSI	Bar
88	31		1053	73
59	15		723	50
32	0		490	34
5	-15		317	22
-22	-30		192	13

 

Above 88°F, CO2 becomes a fluid. Liquid does not exist separate from gas. The pressure in the tank is an indication of the amount of CO2 present in the tank. As the gas is used, the pressure will decline. At 90°F, the pressure in a full cylinder will be approximately 1100-psi.

 

The amount of CO2 in a cylinder is determined by weighing the cylinder containing the CO2 and then subtracting the weight of the empty cylinder which is shown on the cylinder. Below 88°F, the amount of CO2 in the cylinder cannot be estimated by measuring the pressure unless the pressure is less than the vapor pressure shown on the graph. If the pressure is less than the vapor pressure, the container does not contain any liquid CO2 and very little CO2 remains in the container.

 

CO2 is heavier than air and may collect in confined, unventilated areas. Do not permit a leaking cylinder in a closed automobile. CO2 is the regulator of the breathing function, and an increase in the CO2 inhaled will cause an increased rate of breathing. In high concentrations, CO2 can paralyze the respiratory system. Do not breathe air having excessive amounts of CO2.

 

Do not overfill a CO2 container or dangerous pressures can result. Do not use CO2 cylinders, which show any sign of wear, abuse, corrosion, worn threads or any mishandling.

 

 

PHYSICAL CONSTANTS
Density, Gas @ 70°F, 1atm	0.1146 lb/cu ft
Critical Temperature	87.8°F (31°C)
Critical Density	0.468 g/ml
Critical Pressure	1072-psia (73-atm)
Specific Gravity	1.53
Specific Volume @ 70°F, 1-atm	8.76 cu ft/lb or 15,000 cu in/lb or 950 cu in/oz