186 OXYGEN, 



gisticated air, vital air, empyreal or fire air, and pure air, which have 

 all yielded to the name oxygen. 



2. PROCESSES. 



(a.) There are several ; the most useful is by igniting the purest* 

 black oxide of manganese in an iron bottlef or earthen retort ; one 

 ounce of the oxide affords about one hundred and twenty eight cubic 

 inches of gas. 



(6.) Sulphuric acid 1 part, mixed with the same mineral 2 parts, 

 to the consistence of a paste, and heated moderately, affords this 

 gas ; the theory of these experiments will be given hereafter. 



(c.) Other modes will be mentioned farther on, such as that of 

 heating the chlorate or nitrate of potash,{ or a mixture of red lead 

 and sulphuric acid ; and that from green leaves placed in water in 

 the sun's light, &c. The gas is received in inverted glasses full of 

 water. 



3. DISCOVERY 



(a.) By Dr. Priestley,^ in England, August, 1774, by heating 

 red oxide of mercury, in a bell glass by the solar focus. 



(6.) By Scheele, in Sweden, the year after, and without a knowl- 

 edge of Dr. Priestley's discovery ; and also by Lavoisier, at Paris, in 

 the same year. 



4. PHYSICAL PROPERTIES. 



(a.) Transparent, colorless, tasteless, inodorous, not condensible 

 by pressure and cold, a non-conductor of electricity. 



(b.) Sp. gr. 1.1111, air being 1. Thomson. 

 (c.) Wei^ 



ight 33.8888 for 100 cub. in. at the medium temperature 

 and pressure. Id. 



(d.) Refracts light less powerfully than any other gas. 



(e.) Becomes luminous || as well as hot, by sudden condensation. 



(/.) It is a non-conductor of electricity. 



5. CHEMICAL PROPERTIES. 



(a.) It possesses more extensive powers of combination than other 

 substance. 



* It is sometimes previously washed with a weak mineral acid, to decompose car- 

 bonate of lime, if any is present. 



t A wrought iron bottle, with a wide tube about two feet long welded to it, is 

 much the best instrument ; it should be coated, every time it is used, with a lute of 

 clay, sand, and flour, applied with the hand and dried before using. A gun barrel 

 answers for a small experiment. 



t Dr. Thomson says that the first 5th of the gas from nitre is quite pure, and Dr. 

 Hare confirms the statement, that the first portions are quite pure. 



See Priestley's account in his work on air. 



|| All the gases become hot by sudden pressure, but chlorine and oxygen are the 

 only simple gases that become luminous in this manner ; common air becomes 

 luminous by the same treatment, but in a less degree than oxygen, to which gas, 

 this property in air is owing. 



