8 Biographical Account of [Jan, 



weight of inflammable air, zinc about or -JLth of its weight, 

 and tin about -^th of its weight. The properties of the air 

 discharged were the same, whichever of the three metals were 

 used ; and whether they were dissolved in sulphuric or muriatic 

 acids. When the sulphuric acid was concentrated, iron and 

 zinc dissolved in it with difficulty, and only by the assistance of 

 heat. The air given out was not inflammable, but consisted of 

 sulphurous acid. These facts induced Mr. Cavendish to 

 conclude, that the inflammable air evolved in the first case 

 consisted of the unaltered phlogiston of the metals, the sul* 

 phurous acid of the same phlogiston united to a portion of the 

 acid, which deprived it of its inflammability. He found the 

 specific gravity of his inflammable air about 11 times less than 

 tliat of common air. This determination is somewhat less than 

 the truth ; but the error is probably owing chiefly to the quantity 

 of water held in solution by the air, and which Mr. Cavendish 

 showed amounted to ith of the weight of the air. He tried the 

 combustibility of the inflammable air when mixed with various 

 proportions of common air, and found that it exploded with the 

 greatest violence when mixed with rather more than its bulk of 

 common air. 



Copper, he found, when dissolved in muriatic acid by the 

 assistance of heat, yielded no inflammable air ; but an air which 

 losr its elasticity when it came in contact with water. This air, 

 the nature of which Mr. Cavendish did not examine, was 

 muriatic acid gas, the properties of which were soon after 

 investigated by Dr. Priestley. 



The fixed air (now known by the name of carlonic acid gas)^ 

 on which Mr. Cavendish made his experiments, was obtained by 

 dissolving marble in muriatic acid. He found that it might be 

 kept over mercury for any length of time, without undergoing 

 any alteration; that it was gradually absorbed by cold water; 

 and that 100 measures of water, of the temperature of 55*^ 

 absorbed 103*8 measures of fixed air. The whole of the air 

 thus absorbed was separated again by exposing the water to a 

 boiling heat, or by leaving it for some time in an open vessel. 

 Alcohol (the specific gravity of which is not mentioned) dissolved 

 2-^ times its bulk of this air, and olive oil about ^d of its bulk. 

 The specific gravity of fixed air he found I'S?, that of common, 

 air being 1\ Fixed air is incapable of supporting combustion ; 

 and common air, when mixed with it, supports combustion a 

 much shorter time than when pure, A small wax taper burnt 

 80'^, in a receiver which held 1 80 ounce measures, when filled 

 with common air only. The same candle burnt SI'' in the same 

 Receiver, when filled with a mixture of 1 part of fixed air, and 

 19 pf ijommoo air* When the fixed air was of the whok 



