5()4 PHILOSOPHICAL TRANSACTIONS. [ANNO 1784. 



have a power of dephlogisticating the fixed, or phlogisticated, air of the 

 atmosphere. 



" When dephlogisticated and nitrous air are mixed, the dephlogisticated air" 

 seizes part of the phlogiston of the nitrous air." The water contained in the 

 nitrous air, and the other part of the phlogiston, unite with the nitrous acid, 

 which then assumes a liquid form, or at least that of a dense vapour ; " and that 

 part of the latent heat of the 1 airs not essential to the new combination is set 

 at liberty."* In the combustion of sulphur the same thing happens, but in a 

 greater degree ; for the vitriolic acid, having a much weaker attraction for phlo- 

 giston than air has, abandons it almost entirely to the latter, which is thereby 

 converted into water, and reduces it to a liquid state. The same reasoning may 

 be applied to the combustion of phosphorus, which is attended with similar 

 effects. 



15. I shall not make, at present, any further deductions from what I myself 

 consider still in the light of a conjectural hypothesis, which I have perhaps dwelt 

 on too long already. I shall only beg your attention to some general reasoning 

 on the subject ; which however may possibly serve more to show the uncertainty 

 of other systems on the constituent parts of air, than the certainty of this. 

 Some of those systems suppose dephlogisticated air to be composed of an acid 

 and something else, some say phlogiston. If an acid enters into the composi- 

 tion of it, why does not that acid appear again when the air is decomposed, by 

 means of inflammable air and heat ? And why is the water which is the product 

 of this process pure water ? And if an acid forms one of its constituent parts, 

 why has nobody been able to detect any difference in the dephlogisticated air, 

 made by the help of different acids, when compared with each other, or with 

 the air extruded by vegetables? These airs, of such different origins, appear 

 to be exactly the same. And if phlogiston be a constituent part of air, why 

 does it attract phlogiston with such avidity ? Some have, on the other hand, 

 contended that air is composed of earth, united to acids or phlogiston, or to 

 some other matter. Here we must ask, what earth it is which is one of the 

 component parts of air ? All earths which will unite with the nitrous or 

 vitriolic acids, and with some others, such as the phosphoric and the arsenical 

 acids, will serve as bases for the formation of air, and the air produced from all 



* I cannot take on me to determine, from any facts which have come to my knowledge, whe- 

 ther any part of the dephlogisticated air employed in this experiment is turned into fixed air ; but I 

 am rather inclined to think that some part is, because the quantity of heat, which is separated by 

 the union of the two airs, does not seem to be so great as that which is separated when the dephlo- 

 gisticated air is wholly changed into water : yet some water appears to be formed, because when 

 the mixture is made over mercury, the solution of the mercury in the nitrous acid assumes a crys- 

 tallized form, which however may be due to the watery part of the nitrous air. — Orig. 



