VOL. LVI.] PHILOSOPHICAL TRANSACTIONS. 317" 



mixture went otF with a bounce, on applying a piece of lighted paper to the 

 mouth, with exactly the same appearances, as far as I could perceive, as when 

 the phial was filled with the same quantities of common and inflammable air. 



The sugar used in this experiment was moist, and was found to lose -iVoV 

 parts of its weight by drying gently before a fire. Therefore the quantity of dry 

 sugar used was 715 grains; and the weight of the air discharged by fermentation 

 appears to be near 412 grains, i. e. near 1^5- parts of the weight of the dry 

 sugar in the mixture. The fermented liquor was found to have entirely lost its 

 sweetness; so that the vinous fermentation seemed to be completed; but it was 

 not become at all sour. 



Exper. 1. — The air discharged from apple-juice, by fermentation, was tried 

 exactly in the same manner. The quantity set to ferment was 7060 grains, and 

 was mixed with lOO grains of yeast. Some of the same parcel of apple-juice, 

 being evaporated gently to the consistence of a moderately hard extract, was 

 reduced to J- of its weight; so that the quantity of extract, in the 7060 grains 

 of juice employed, was lOOQ grains. The liquor fermented much faster than 

 the sugar and water. The loss of weight during the fermentation was 384 

 grains. The air remaining unabsorbed in the inverted bottle of soap leys was 

 lost by accident, so that it could not be measured; but, from the space it took 

 up in the inverted bottle, I think I may be certain that it could not much exceed 

 the empty space in the bent tube and fermenting bottle, if it did at all. There- 

 fore there is no reason to think that the apple-juice, any more than the sugar 

 and water, produced any kind of air during the fermentation, except fixed air. 

 It appears too, that the fixed air was near -,VoV of the weight of the extract 

 contained in the apple-juice. The fermented liquor was very sour; so that it 

 had gone beyond the vinous fermentation, and made some progress in the 

 acetous fermentation. In order to compare more exactly the nature of the air 

 produced from sugar by fermentation, with that produced from marble by 

 solution in acids, I made the three following experiments: 



Exper. 3. — I first tried in what quantity the air from sugar was absorbed by 

 water, and at the same time made a like experiment on the air discharged fi-om 

 marble, by solution in spirit of salt. This was done exactly in the same way 

 as the former experiments of this kind. The result is as follows, beginning 

 with the air from sugar and water. 



Air from sugar and water let up= 1000. 

 Balk of water let up Bulk of air Whole bulk of Whole bulk Bulk of air re- Height of ther- 



eachtime. absorbed of water of air maining. mometerwhen 



each lime. letup. absorbed- obs. was made. 



375 517 375 517 483 40 



143 164 518 681 319 45 



163. 164 673 845. 154 45 



82 103 755 948 62 46 



