4IO Exper'mints on Fermentation. 



placed under a glafs bell. The temperature of the room during the whole of this experi- 

 ment was rather high, and varied froni 68° to 75° ot.Fahrenlicit. 



The laft mixture began to ferment in 12 hours, and in 24 the procefs feemed very brifk, 

 .much water now condenfing on the fides of the bell. In five days the procefs began to fub- 

 fuie ; in feven, the yealt fell to the bottom, and the liquor became clear. The mixture, 

 at this time, fmelled ftrongly of beer turned a little four, although it ftill tailed fweet- 

 ifh. It was fuffered to remain until the 28th, when it was removed from the bell and 

 weighed, and the lofs was found to exceed three drachms : it now tailed much like a mixture 

 of flrong vinegar and honey. During the whole of this period, amounting to ^14 days, 

 the mixture, containing the fugar digefted with the lime, never fliewed the lead appear- 

 ance of fermentation, nor was there any moifture condenfed on the fides of the bell. The 

 veflel and mixture being now weighed, the lofs amounted to two drachms nearly; the li- 

 quor fmelled very mully, and had a rough aflringcnt tafte, mixed with fweetnefs, but was 

 not in the leaft acid. In this inllance the yeall fell to the bottom very foon, the liquor 

 continued more or lefs mouldy, and became, at lall, a little mouldy at the top. 



We next digefted an ounce of fugar, diflblved in five ounces of water, with a little pot- 

 afh, and to the filtered folution added about two drachms of very good yeall. This mix- 

 ture was expofed in an open veflel to a tem.perature of about 65°; and another veflel, con- 

 taining a folution of an equal quantity of fugar, mixed with yeaft, placed by it as a 

 ftandard. 



The folution with the yeaft alone began to ferment in 12 hours ; but the other, contain- 

 ing the pot-alh, fliewed no fymptoms of fermentation at the end of 12 days. 



Being now in a great meafure fatisfied, that any fourth fubftance combined, although in 

 fmall quantity, with the three which form fugar, would prevent fermentation, we next %vifticd 

 to know if every compound, confifting of carbon, hydrogen, and oxygen, however differently 

 thefe fubftances might be proportioned, were fufceptible of its procefs. The fugar of milk, 

 from what has already been obferved, evidently confifts of thefe three fimple fubftances; but, 

 from a number of its fenfible properties, and the refult of its analyfis by heat, as well as 

 its containing the radical of the facchola£lic acid, it is manifeft that their combinations 

 and proportions muft be very different from thofe in common fugar. 



"We therefore mixed a folution of its faccharine matter with the ufual quantity of yeaft, 

 and expofed it to a temperature ranging from 65° to 70°: in four days fome degree of 

 fermentation was perceptible, and in three days more, became brilk : at the end of fixteen, 

 when its procefs had apparently ceafed, the liquor was examined : it now had the fmell 

 of cyder, but rather more of the flavour of apples ; to the tafte it was very four, and, 

 when added to the tin£lure of litmus, ftrongly reddened it. 



The acid thus procured either contained or confifted of common vinegar; for with the 

 oxyde of lead it formed a fweet faline mafs, compofed evidently of flcnder prifmatic 

 cryftals which were not deliquefcent.* 



Hence it is manifeft, that the fugar of milk is at leaft in fome degree fufceptible of 

 the vinous fermentation. 



Having obferved, in our attempts to convert gum into £iigar, that it feemed to run eafily 

 intp the acid ftatc, we were anxious to know if any thing like fermentation preceded this 



■* See Scheele's Efiays, page 174. 



ftate, 



