4Q6 philosophical transactions. [anno 1788. 



mixed with hepatic air, volatile alkali will be formed. Dr. A. often repe aed 

 this experiment, and marked the formation of the volatile alkali by the change 

 of the vegetable blue to a green colour. In hepatic air the parts of inflam- 

 mable air are brought nearer to each other than they are in their simple aeriform 

 state,* and therefore the phlogisticated air of the nitrous air combines with 

 them, and generates volatile alkali. 



From all these experiments it follows, that whether phlogisticated air be in a 

 state of purity, or mixed with dephlogisticated air, as in the atmosphere, or 

 combined with it as in nitrous air, it will in either case unite with the gravi- 

 tating matter of light inflammable air, provided this substance be presented to it 

 in a state of condensation ; but if the circumstances be reversed, the same com- 

 bination does not take place. No union is formed between inflammable air and 

 the phlogisticated part of nitrous air, even though marine acid be added, which, 

 by its attraction to dephlogisticated air, would contribute to decompose the 

 nitrous air, and by its attraction to volatile alkali would tend to unite its consti- 

 tuent parts: or if to light inflammable air we add nitrous air and iron filings, no 

 combination ensues; though it has been often observed that volatile alkali is 

 readily generated, when nitrous air is presented to the inflammable at the instant 

 of its extrication from water and iron. 



The proportions of the phlogisticated and inflammable airs in volatile alkali, 

 as discovered by calculation, approach very near to the result of M. Berthollet's 

 experiments. If we take the specific gravities of these airs, given in 

 Mr. Kirwan's late publication. 



100 cubic inches contain 18.1 6 grains of alkaline air. 



30.535 .... of phlogisticated air. 



2.6l3 .... of inflammable air. 



According to M. BerthoUet alkaline air is expanded on decomposition from I.7 

 to 3.3. Its specific gravity after decomposition must therefore be lessened in 

 the same proportion; and 100 cubic inches will be found to contain only 9.355 

 grains of alkaline air thus expanded. In what proportion must the phlogisti- 

 cated and inflammable airs be, in order to form a mixture of this specific 

 gravity ? 



Let X represent the number of grains of phlogisticated air in 100 cubic inches 

 of the mixture : then 9-355 — a; will express the number of grains of inflam- 

 mable air. As the weight of 1 cubic inch is to a cubic inch, so will the 

 * After these experiments were made. Dr. A. found that this is not the case. The electric spark 

 decomposes hepatic air, and leaves a quantity of inflammable air equal in bulk to the hepatic air 

 very nearly. However, as the inflammable air leaves the sulphur on the application of the electrical 

 spark, it should seem that the proper matter of inflammable air is more disposed to combine with 

 fire than with sulphur ; which may be the reason why hepatic air is decomposed by nitrous air, 

 while pure inflammable air is not afi'ected by it. — Orig. 



