306 PHILOSOPHICAL TRANSACTIONS. [aNNTO I76O. 



Strong spirit of salt, the loss in efFervescence was 14^ grains, the empty space 

 873 grain measures: therefore the weight of the inflammable air was 13^ grains 

 i. e. Vt of the weight of the tin, and its density 89 1 8 times less than that ot 

 water. The quantity of moisture condensed was about 3 grains. 



It is evident, that the truth of these determinations depend son a supposition, 

 that none of the inflammable air is absorbed by the pearl-ashes. In order to see 

 whether this was the case or no, I dissolved 86 grains of zinc in diluted acid of 

 vitriol, and received the air in a measuring bottle in the common way. Immedi- 

 ately after, I dissolved the same quantity of zinc in the same kind of acid, and 

 made the air to pass into the same measuring bottle, through a cylinder filled 

 with dry pearl-ashes, in the manner represented in Fig. 17. I could not perceive 

 any difference in their bulks. 



It appears from these experiments, that there is but little, if any, difference in 

 point of density between the different sorts of inflammable air. Whether the 

 difference of density observed between the air procured from zinc, by the vitriolic 

 and that by the marine acid is real, or whether it is only owing to the error of 

 the experiment, I cannot pretend to say. By a medium of the experiments, in- 

 flammable air comes out 8760 times lighter than water, or 1 1 times lighter than 

 common air. 



In order to see whether inflammable air, in the state in which it is, when con- 

 tained in the inverted bottles, where it is in contact with water, contains any 

 considerable quantity of moisture dissolved in it, I forced 192 ounce measures 

 of inflammable air, through a cylinder filled with dry pearl-ashes, by means of 

 the same apparatus, which I used for filling the bladders with inflammable air, 

 and which is represented in fig. 15. The cylinder was weighed carefully before 

 and after the air was forced through ; by which it was found to have increased 1 

 grain in weight. The empty space in the cylinder was 248 grains, the difference 

 of weight of which quantity of common and inflammable air is ^ of a grain. 

 Therefore the real quantity of moisture condensed in the pearl-ashes is 1^ grain. 

 The weight of 192 ounce measures of inflammable air deprived of its moisture 

 appears from the former experiments to be 1 04 grains ; therefore its weight when 

 saturated with moisture would be 1 1 -•- grains. Therefore inflammable air, in that 

 state in which it is in, when kept under the inverted bottles, contains near ^ its 

 weight of moisture ; and its specific gravity in that state is 7840 times less than 

 that of water. 



I made an experiment with design to see, whether copper produced any in- 

 flammable air by solution in spirit of salt. I could not procure any inflammable 

 air by it : but the phenomena attending it seem remarkable enough to deserve 

 mentioning. The apparatus used for this experiment was of the same kind as 

 was represented in fig. 13. The bottle a was filled almost full of strong spirit 



