2,60 PHILOSOPHICAL TRANSACTIONS. [ANNO 1/8 2. 



One measure of the purest dephlogisticated air and 2 of nitrous air occupy 

 only T » T parts of one measure, as Dr. Priestley has observed, vol. 4, p. 245. 

 Suppose 1 measure to contain 100 cubic inches, then the whole very nearly of 

 the nitrous air will disappear, its acid uniting to the water over which the expe- 

 riment is made, and 97 cubic inches of the dephlogisticated air, which is con- 

 verted into fixed air by its union with the phlogiston of the nitrous air ; therefore 

 97 cubic inches of dephlogisticated air take up all the phlogiston which 200 

 cubic inches of nitrous air will part with ; and this we have found to be 7 grains; 

 therefore, a weight of fixed air, equal to that of 97 cubic inches of dephlogisti- 

 cated air and 7 of phlogiston, will contain 7 gr. of phlogiston. Now, Q7 cubic 

 inches of dephlogisticated air weigh 40.74 gr. ; to which adding 7 gr. we have 

 the whole weight of the fixed air equal 47.74 gr. = 83.755 cubic inches; and 

 consequently 100 cubic inches of fixed air contain 8.357 gr. of phlogiston, and 

 the remainder elementary air. 



100 gr. of fixed air contain 14.66 1 of phlogiston and 85.33g of elementary 

 air ; which, when stripped of phlogiston, and impregnated with its proper pro- 

 portion of elementary fire, becomes again dephlogisticated air. Hence also 100 

 cubic inches of dephlogisticated air are converted into fixed air by 7.21 65 gr. of 

 phlogiston, and will be then reduced to the bulk of 86.34 cubic inches. And 

 reciprocally, 100 cubic inches of fixed air, being decomposed, will afford 

 1 15.821 cubic inches of dephlogisticated air, and part with 7.2165 gr. of phlo- 

 giston, supposing the decomposition to be complete ; that is, the dephlogisti- 

 cated air absolutely pure. 



Of the quantity of phlogiston in vitriolic air. — The method I pursued was this: 

 1st. I found the quantity of nitrous air a given weight of copper afforded when 

 dissolved in the dephlogisticated nitrous acid, and by that means how much 

 phlogiston it parts with. 2dly. I found the quantity of copper which a given 

 quantity of the dephlogisticated vitriolic acid could dissolve ; and observed, that 

 it could not dissolve the greatest quantity of copper without dephlogisticating a 

 further quantity which it does not dissolve. 3dly. 1 found how much it dephlo- 

 gisticates what it thoroughly dissolves, and how much it dephlogisticates what it 

 barely calcines. 4thly. How much inflammable air a given quantity of copper 

 affords when dissolved in the vitriolic acid to the greatest advantage. 5thly. I 

 deduct from the whole quantity of phlogiston expelled by the vitriolic acid the 

 quantity of it contained in the inflammable air ; the remainder shows the quan- 

 tity of it contained in the vitriolic air. 



The particulars were as follow : — 1st. 100 gr. of copper dissolved in the de- 

 phlogisticated nitrous acid afforded 67.5 cubic inches of nitrous air, which, 

 according to the before-mentioned calculation, contain 4.52 gr. of phlogiston. 

 2dly. 100 gr. of real vitriolic acid take up or dissolve 54.73 of copper, and 100 



