488 PHILOSOPHICAL TRANSACTIONS. [ANNO 1784. 



measures, furnished with a brass cock, and an apparatus for firing air by electri- 

 city. This globe was well exhausted by an air-pump, and then filled with a mix- 

 ture of inflammable and dephlogisticated air, by shutting the cock, fastening a 

 bent glass tube to its mouth, and letting up the end of it into a glass jar inverted 

 into water, and containing a mixture of 19500 grain measures of dephlogisti- 

 cated air, and 37000 of inflammable ; so that, on opening the cock, some of 

 this mixed air rushed through the bent tube, and filled the globe.* The cock 

 was then shut, and the included air fired by electricity ; by which means almost 

 all of it lost its elasticity. The cock was then again opened, so as to let in more 

 of the same air, to supply the place of that destroyed by the explosion, which 

 was again fired, and the operation continued till almost the whole of the mix- 

 ture was let into the globe and exploded. By this means, though the globe held 

 not more than the 6th part of the mixture, almost the whole of it was exploded 

 in it, without any fresh exhaustion of the globe. 



As I was desirous to try the quantity and test of this burnt air, without 

 letting any water into the globe, which would have prevented my examining the 

 nature of the condensed matter, I took a larger globe, furnished also with a 

 stop cock, exhausted it by an air-pump, and screwed it on the cock of the former 

 globe ; then, by opening both cocks, the air rushed out of the smaller globe 

 into the larger, till it became of equal density in both ; then, by shutting the 

 cock of the larger globe, unscrewing it again from the former, and opening it 

 under water, I was enabled to find the quantity of the burnt air in it ; and con- 

 sequently, as the proportion which the contents of the 2 globes bore to each 

 other was known, could tell the quantity of burnt air in the small globe before 

 the communication was made between them. By this means the whole quantity 

 of the burnt air was found to be 2950 grain measures; its standard was 1.85. 

 The liquor condensed in the globe, in weight about 30 grs., was sensibly acid to 

 the taste, and by saturation with fixed alkali, and evaporation, yielded near 

 2 grs. of nitre ; so that it consisted of water united to a small quantity of nitrous 

 acid. No sooty matter was deposited in the globe. The dephlogisticated air 

 used in this experiment was procured from red precipitate, that is, from a solution 

 of quicksilver in spirit of nitre distilled till it acquires a red colour. 



• As it was suspected, that the acid contained in the condensed liquor was no 

 essential part of the dephlogisticated air, but was owing to some acid vapour 

 which came over in making it, and had not been absorbed by the water, the 

 experiment was repeated in the same manner, with some more of the same air, 

 which had been previously washed with water, by keeping it a day or 2 in a 



* In order to prevent any water from getting into this tube, while clipped under water to let it up 

 into the glass jar, a bit of wax was stuck on the end of it, which was rubbed oil' when raised above 

 the surface of the water.— Orig. 



