ON ATMOSPHERICAL AIR, |^7 



Nos. 25, 26, refults of coal. No. 25, produced by the 

 fufion of common coal under preffure in low red heat. It 

 gave flame powerfully. No. 26, coal produced from horn. 

 It is a fliining black fubflance, exadly refembling pitch or pe- 

 troleum, and burns with a bright flame, 



JAMES HALL. 



IX. 



Atmofpherical Air not a mechanical Mixture of the Oxigenovs and 

 Azotic Gajh, demonjlrated from the Specific Gravities of thejh 

 Fluids, In a Letter from Mr. John Gough. 



To Mr. NICHOLSON. 

 SIR, 



JL HAVE already attempted to prove common air not to be a Introduftory re- 

 mechanical mixture. The arguments which I ufed for the^^*^^^* 

 purpofe, were drawn from the properties of refrafled light 

 and the motion of founds through elaftic fluids. Such proofs 

 are of an indire6l nature; and though the mathematician may 

 fee the force of them, they may not carry an equal degree of 

 convidion to the chemifl, who ought alfo to be convinced. 

 The following obfervations apply more immediately to the 

 fubjedl ; and I do not perceive how they can be refuted, unlefs 

 this be done by difputing the accuracy of the experiments on 

 which they are founded. The prefent enquiry has the re- Experlmenbfl 

 commendation of being ftatical, and the data of my calcula- '^^^^^ 

 tions are borrowed from certain experiments made by Mr. 

 Kirwan and M. Lavoifier. According to (he former gentle- 

 man, if the weight * of atmofpherical air be denoted by 1000, 

 that of an equal bulk of carbonic acid gas will be 1500, of 

 oxigenous gas 1103, of azotic gas 985. An attempt to dif- 

 cover the comparative weights of a number of gafes is a diffi- 

 cult undertaking; but the preceding ratios may be ufed with 

 fome degree of confidence, becaufe they have been eftabliflied 

 by a philofopher of the higheft reputation. Then in order to 

 apply them to the bufinefs in hand, we will fuppofethe weight 

 of 100 cubic inches of common air to be denoted by unity; 

 though the real weight of the quantity may be ftaled at 3\ Equations to 



♦EffayonPhlogiflon. baV.'''"^'^ 



g 



rams. 



