1(4 



AGRICULTURAL CHEMISTRY. 



The alcohol and carbonic acid are pro- 

 duced from the elements of the sugar, and 

 tne ferment from those azotised constituents 

 of the grape -juice, which have been termed 

 gluten, or vegetable albumen. 



According to the experiments of De 

 Saussure, fresh impure gluten evolved, in 

 five weeks, twenty-eight times its volume of 

 a gas which consisted f of carbonic acid, 

 and of pure hydrogen gas ; ammoniacal 

 salts of several organic acids were formed 

 at the same time. Water must, therefore, 

 Le decomposed during the putrefaction of 

 gluten ; the oxygen of this water must enter 

 into combination with some of its consti- 

 tuents, whilst hydrogen is liberated, a cir- 

 cumstance which happens only in decom- 

 positions of the most energetic kind. Nei- 

 ther ferment nor any substance similar to it 

 is formed in this case ; and we have seen 

 that in the fermentation of saccharine vege- 

 table juices, no escape of hydrogen gas takes 

 place. 



It is evident that the decomposition which 

 gluten suffers in an isolated state, and that 

 which it undergoes when dissolved in a ve- 

 getable juice, belong to two different kinds 

 of transformations. There is reason to be- 

 lieve that its change to the insoluble state 

 depends upon an absorption of oxygen, for 

 its separation in this state may be effected, 

 nnder certain conditions, by free exposure 

 '. tho a ; r, without the presence of ferment- 

 ing sugar. It is known also that the juice 

 of" grapes, or vegetable juices in general, 

 become turbid when in contact with air, be- 

 fore fermentation commences ; and this tur- 

 bidity is owing to the formation of an inso- 

 luble precipitate of the same nature as fer- 

 ment. 



From the phenomena which have been 

 observed during the fermentation of wort,* it 

 is known with perfect certainty- that ferment 

 is formed from gluten at the same time that 

 the transformation of the sugar is effected ; 

 for the wort contains the azotised matter of 

 the corn, namely, gluten in the same condi- 

 tion as it exists in the juice of grapes. The 

 wort ferments by the addition of yeast, but 

 after its decomposition is completed, the 

 quantity of ferment or yeast is found to be 

 thirty times greater than it was originally. 



Yeast from beer and that from wine, ex- 

 amined under the microscope, present the 

 / same form and general appearance. They 

 are both acted on in the same manner by 

 alkalies and acids, and possess the power of 

 inducing fermentation anew in a solution of 

 sugar ; in short, they must be considered 

 as identical. 



The fact that water is decomposed during 

 the putrefaction of gluten has been com- 

 pletely proved. The tendency of the carbon 

 of the gluten to appropriate the oxygen of 

 water must also always be in action, whether 

 the gluten is decomposed in a soluble or in- 



* Wort is an infusion of malt ; it consists of the * The liquid expressed from grapes when fully 

 noluble parts of this substance dissolved in water, i ripe is called must. 



soluble state. These considerations, there- 

 fore, as well as the circumstance which al) 

 the experiments made on this subject appear 

 to point out, that the conversion of gluten 

 to the insoluble state is the result of oxida- 

 tion, lead us to conclude that the oxygen 

 consumed in this process is derived from the 

 elements of water, or from the sugar which 

 contains oxygen and hydrogen in the same 

 proportion as water. At all events, the oxy 

 gen thus consumed in the fermentation of 

 wine and beer is not taken from the atmo 

 sphere. 



The fermentation of pure sugar in con 

 tact with yeast must evidently be a very dif- 

 ferent process from the fermentation of 

 wort or must.* 



In the former case, the yeast disappears 

 during the decomposition of sugar ; but in 

 the latter, a transformation of gluten is 

 effected at the same time, by which ferment 

 is generated. Thus yeast is destroyed in the 

 one case, but is formed in the other. 



Now since no free hydrogen gas can be 

 detected during the fermentation of beer and 

 wine, it is evident that the oxidation of the 

 gluten, that is, its conversion into ferment, 

 must take place at the cost either of the oxy- 

 gen of the water, or of that of the sugar ; 

 whilst the hydrogen which is set free must 

 enter into new combinations, or by the de- 

 oxidation of the sugar, new compounds con- 

 taining a large proportion of hydrogen, and 

 small quantity of oxygen, together with the 

 carbon of the sugar, must be formed. 



It is well known that wine and fermented 

 liquors generally contain, in addition to the 

 alcohol, other substances which could not 

 be detected before their fermentation, and 

 which must have been formed, therefore, 

 during that process in a manner similar to 

 the production of mannite. The smell and 

 taste which distinguished wine from all 

 other fermented liquids are known to depend 

 upon an ether of a volatile and highly com- 

 bustible acid ; the ether is of an oily nature, 

 and has received the name (Enanthic ether. 

 It is also ascertained that the smell and taste 

 of brandy from corn and potato are owing 

 to a peculiar oil, the oil of potatoes. This 

 oil is more closely allied to alcohol in its 

 properties, than to any other organic sub- 

 stance. 



These bodies are products of the deoxida- 

 tion of the substances dissolved in the fer- 

 menting liquids ; they contain less oxygen 

 than sugar or gluten, but are remarkable for 

 the large quantity of hydrogen which enters 

 into their composition. 



(Enanthic acid contains an equal number 

 of equivalents of carbon and hydrogen, 

 exactly the same proportions of these ele- 

 ments, therefore, as sugar, but by no means 

 the same proportion of oxygen. The oil of 

 potatoes contains much more hydrogen. 

 Although it cannot be doubted that these 



