VOL. LVI.] PHILOSOPHICAL TRANSACTIONS. 3lg 



received in an empty bladder, and thence transferred into the inverted bottles of 

 water in which it was measured; for the air is produced from the sugar so slowly, 

 that if it had been received in the inverted bottles immediately, it would have been 

 absorbed almost as fast as it was generated. 



It appears from these experiments, that the air produced from sugar by 

 fermentation, and in all probability that from all the other sweet juices of 

 vegetables, is of the same kind as that produced from marble by solution in 

 acids, or at least does not differ more from it than the different parts of that air 

 do from each other, and may therefore justly be called fixed air. I now proceed 

 to the air generated by putrifying animal substances. 



Exper. 6 — The air produced from gravy broth by putrefaction, was forced 

 into an inverted bottle of soap leys, in the same way as in the former experiment. 

 The quantity of broth used, was 7640 grains, and was found, by evaporating 

 some of the same to the consistence of a dry extract, to contain 1 63 grains of 

 solid matter. The fermenting bottle was immersed in water kept constantly to 

 the heat of about 96°, In about two days the fermentation seemed entirely 

 over. The liquor smelt very putrid, and was found to have lost 1 \\ grains of 

 its weight. The soap leys had acquired a brownish colour from the putrid 

 vapours, and a musty smell. The air forced into the inverted bottle, and not 

 absorbed by the soap leys, measured 6280 grains: the air left in the 

 bent tube and fermenting bottle was 1100 grains; almost all of which 

 must have been forced into the inverted bottles: so that this unabsorbed air is a 

 mixture of about 1 part of common air and 4-t^ of factitious air. 



The air was found to be inflammable; for a small phial being filled with ICQ 

 grain measures of it, and 301 of common air, which comes to the same thing 

 as 90 grains of pure factitious air, and 320 of common air, it took fire on applying a 

 piece of lighted paper, and went off with a gentle bounce, of much the same 

 degree of loudness as when the phial was filled with the last mentioned quantities 

 of inflammable air from zinc, and common air. When the phial was filled with 

 297 grains of this air, and 113 of common air, i. e. with 245 of pure factitious 

 air, and l65 of common air, it went off with a gentle bounce on applying the 

 lighted paper ; but I think not so loud as when the phial was filled with the last- 

 mentioned quantities of air from zinc and common air. 



5500 grain measures of this air, i.e. 4540 of pure factitious air, and 960 of 

 common air, were forced into a piece of ox-gut furnished with a small brass cock, 

 which I find more convenient for trying the specific gravity of small quantities 

 of air, than a bladder : the gut increased 44- grains in weight on forcing out the 

 air. A mixture of 4540 grains of air from zinc, and 960 of common air being 

 then forced into the same gut, it increased 44- grains on forcing out the air. So 



