RESEARCHES UPON THE CHEMICAL PROPERTIES OF GASES. 217 



but trials with different pressures showed greater constancy than could be antici- 

 pated from a method so rough in appearance. The results corroborate those 

 obtained by the more delicate tests. Experiments have also been tried with mix- 

 tures of air and natural gas which were exposed to palladium asbestos contained in 

 glass tubes heated in the iron oven described under " Oxidation Temperatures of 

 Hydrocarbons." It has been repeatedly shown that, under such conditions, moisture 

 is only produced at temperatures approaching or higher than the melting point of 

 cadmium iodide. 



The absence of fi"ee hydrogen has interfered with the use of natural gas in gas 

 engines. The prompt, sharp explosion of coal gas, so necessary for these motors, 

 cannot be produced in the case of natural gas which requires a higher temperature 

 for its ignition, and explodes with less suddenness owing to the absence of hydrogen. 



The electrical devices for the igniting of coal-gas jets in dwellings by the spark 

 of an induction coil, have not been so successful where natural gas is used, owing to 

 the higher temperature of ignition of a gas consisting of paraffins and containing no 

 hydrogen. In laboratories where natural gas is the fuel, chemists have experienced 

 the inconvenience that Bunsen burners and blast lamps do not produce the high tem- 

 perature easily obtained when coal gas is used. Ordinary glass combustion tubing 

 cannot be softened by the employment of natural gas in a Berzelius blast lamp. 



A coal-gas flame owes its steadiness and " stiffness " to the hydrogen which the 

 gas contains. N^atural-gas flames are much less steady and more easily extinguished 

 by air currents. 



During May, 1892, a change occurred in the composition of the natural gas 

 supplied to Allegheny City. The gas since that time and up to November, 1892, 

 has been found to contain hydrocarbons which reduce dry palladium chloride. These 

 hydrocarbons are removed completely by digestion with fuming sulphuric acid, so 

 that the gas after this treatment does not reduce palladium chloride. The nature of 

 these hydrocarbons I have been unable yet to determine. 



OLEFINES. 



Palladium chloride, iridium chloride, cerium dioxide in sulphuric acid, osmic 

 acid, all remain unchanged by natural gas, cold or at 100°. Potassium permanga- 

 nate is attacked with extreme slowness. 



Bromine water has been repeatedly tried. The solution was in some cases 

 cooled by ice to check evaporation of the bromine and in others the bromine was 

 added slowly, drop by drop, to compensate for its evaporation. In no case were any 

 oily drops produced. Prof. Sadtler, of Philadelphia, has in one instance obtained a 

 considerable amount of heavy oil by the action of bromine on natural gas. 



