THOMPSON. — ON THE EQUILIBRIUM OF THE SYSTEM. 439 



or 7-?h 2 o = 0.003 pco, which is a negligible quantity. The tempera- 

 ture of the gas, however, is not all at 1500°, but falls off to the tem- 

 perature of the water cooled walls of the furnace. At 1000° C. pmo 

 = .063 pco which is still a relatively small amount. What actually 

 happens is that at the higher temperatures where the velocity of the 

 reaction is great, the equilibrium varies uniformly with the tempera- 

 ture, but as the gas reaches the cooler portions of the furnace, due to 

 convection currents, it suddenly becomes chilled to a point where the 

 reaction practically stops, leaving the concentrations at values corre- 

 sponding to the higher temperatures. 



Experiment 1. 



The charge consisted of lime, carbon, and calcium carbide mixed to- 

 gether. A loosely fitting lid with a quarter-inch hole in the center 

 covered the crucible. The mixture was placed in the furnace, the 

 furnace was evacuated, and the charge heated to 1000° for an hour to 

 drive off gases that invariably come off on the first heating, and par- 

 ticularly to get rid of any water contained as hydrate of calcium. If 

 this were not done water would come off during the run and react with 

 the carbide present. The furnace was then evacuated to a pressure of 

 0.05 centimeters of mercury and carbon monoxide let in to 1.25 centi- 

 meters. This was generated from strong sulphuric acid and potassium 

 ferrocyanide and was washed with two drying towers of soda lime and 

 a phosphorous pentoxide tube. Hydrogen was then admitted to a 

 final pressure of 63.6 centimeters. This was generated from hydro- 

 chloric acid and zinc and was purified by two bottles of permanganate, 

 a hot copper gauze, two towers of soda lime, and a phosphorus pen- 

 toxide tube. The furnace was filled with hydrogen in three quarters 

 of an hour. The volume of the furnace, after allowing for the solids 

 present during a run was 19.9 liters. The run began at 9.45 a. m. and 

 lasted till 4.00 p. m. The power was held constant at 12.0 kilowatts 

 corresponding to 1485° C. The following table gives the analysis for 

 carbon monoxide, made by drawing off 100 cubic centimeters into a 

 Hempel burette and absorbing with acid cuprous chloride solution. 



Time. Per cent Carbon Monoxide. 



9.45 a. m. Sample taken as furnace 1.05 



warmed up. 

 1.42 p. M. Less than 0.1 



It was evident from this result that the quantity of gas corresponding 

 to equilibrium at this temperature could not be analyzed by a Hempel 



