56(j PHILOSOPHICAL TRANSACTION. [ANNO 1784. 



Fahrenheit's scale, each ounce of air gave out 68.634 X 135° = g265°.5gO ; 

 that is to say, a quantity of heat which would have heated 1 oz. of water, or 

 any other matter which has the same capacity for receiving heat as water has, 

 from 32° to Q263+ : a surprizing quantity ! (It is to be understood, that all 

 the latent heats mentioned herein are compared with the capacity of water). 

 And when 1 oz. of dephlogisticated air was changed into fixed air, by burning 

 charcoal, or by the breathing of animals, it melted 29. 547 oz. of ice : conse- 

 quently we have 29.547 X 135°= 3988°.845, the quantity of heat which an 

 ounce of dephlogisticated air loses when it is changed into fixed air. By the 

 heat extricated during the detonation of 1 oz. of nitre with 1 oz. of sulphur, 32 

 oz. of ice were melted ; and, by the experiment I have mentioned of Dr. 

 Priestley's (6), it appears that nitre can produce one half of its weight of dephlo- 

 gisticated air. When the nitre and sulphur are kindled, the dephlogisticated 

 air of the nitre unites with the phlogiston of the sulphur, and sets its 

 acid free, which immediately unites to the alkali of the nitre, and produces 

 vitriolated tartar. The dephlogisticated air, united to the phlogiston, is turned 

 into water, part of which is absorbed by the vitriolated tartar, and part is dissi- 

 pated in the form of vapours, or unites to the nitrous air, or other air, produced 

 in the process. 



As 4- an oz. of dephlogisticated air is, in this process, united by inflammation 

 to a quantity of phlogiston sufficient to saturate it, and no fixed air is produced, 

 it should melt a quantity of ice equal to the half of what was melted by the com- 

 bination of 1 oz. of air with phlogiston in burning phosphorus ; that is, it 

 should melt 34.317 oz. of ice; and we find, by Messrs. Lavoisier and De la 

 Place's experiment, that it actually melted 32 oz. of ice : the small difference 

 may be accounted for by supposing, that the heat produced by the combustion 

 might not be quite so great as that Dr. Priestley employed in his experiment ; or 

 that the nitre might be less pure, and consequently not so much air formed. 

 The two facts, however, agree near enough to permit us to conclude, that de- 

 phlogisticated air, in uniting to the phlogiston of sulphur, produces as much 

 heat as it does in uniting with the phlogiston of phosphorus. 



17. According to Dr. Priestley's experiments, dephlogisticated air unites com- 

 pletely with about twice its bulk of the inflammable air from metals. The 

 inflammable air being supposed to be wholly phlogiston, and being ? ' T of the 

 weight of an equal bulk of dephlogisticated air, and being double in the quan- 

 tity, will be T jj. of the weight of the dephlogisticated air it unites with. There- 

 fore 1 oz. (576 grains) of dephlogisticated air will require 120 grs. of inflam- 

 mable air, or phlogiston, to convert it into water. And supposing the heat 

 extricated by the union of dephlogisticated and inflammable air to be equal to 

 that extricated by the burning of phosphorus, we shall find, that the union of 



