VOL. LVI.] PHILOSOPHICAL TRANSACTIONS. 301 



froin animal substances in putrefaction, and from vegetable substances in distilla- 

 tion, as will be shown hereafter ; though there can be no reason to suppose that 

 this kind of inflammable air owes its production to any acid. I now proceed to 

 the experiments made on inflammable air. 



I cannot find that this air has any tendency to lose its elasticity by keeping, or 

 that it is at all absorbed, either by water, or by fixed or volatile alkalies; as I 

 have kept some by me for several weeks in a bottle inverted into a vessel of water, 

 without any sensible decrease of bulk ; and as I have also kept some for a few 

 days, in bottles inverted into vessels of soap lees and spirit of sal ammoniac, 

 without perceiving their bulk to be at all diminished. 



It has been observed by others, that when a piece of lighted paper is applied 

 to the mouth of a bottle, containing a mixture of inflammable and common air, 

 the air takes fire, and goes off" with an explosion. In order to observe in what 

 manner the eftect varies according to the different proportions in which they are 

 mixed, the following experiment was made. Some of the inflammable air, pro- 

 duced by dissolving zinc in diluted oil of vitriol, was mixed with common air in 

 several different proportions, and the inflammability of these mixtures tried one 

 after the other in this manner. A quart bottle was filled with one of these mix- 

 tures, in the manner represented in fig. 14. The bottle was then taken out of 

 the water, set upright on a table, and the flame of a lamp or piece of lighted 

 paper applied to its mouth. But, in order to prevent the included air from mix- 

 ing with the outer air, before the flame could be applied, the mouth of the bottle 

 was covered, while under water, with a cap made of a piece of wood covered 

 with a few folds of linen; which cap was not removed till the instant that the 

 flame was applied. The mixtures were all tried in the same bottle; and as they 

 were all ready prepared, before the inflammability of any of them was tried, the 

 time elapsed between each trial was but small : by which means I was better able 

 to compare the loudness of the sound in each trial. The result of the experi- 

 ment is as follows. 



With one part of inflammable air to g of common air, the mixture would not 

 take fire, on applying the lighted paper to the mouth of the bottle; but on put- 

 ting it down into the belly of the bottle, the air took fire, but made very little 

 sound. With 2 parts of inflammable to 8 of common air, it took fire immedi- 

 ately, on applying the flame to the mouth of the bottle, and went off" with a 

 moderately loud noise. With 3 parts of inflammable air to 7 of common air, 

 there was a very loud noise. With 4 parts of inflammable to 6 of common air, 

 the sound seemed very little louder. With equal quantities of inflammable and 

 common air, the sound seemed much the same. In the first of these trials, 

 namely, that with one part of inflammable to 9 of common air, the mixture did 

 not take fire all at once, on putting the lighted paper into the bottle; but one 



