HOW AND WHY VINEGAR IS FORMED. 133 



already seen that the starch of the seed (C12 H^o Oio) "^^y he repre- 

 sented by carbon and water, — by 12C + lOHO. Now it appears tbat 

 in contact with the oxygen of the atmosphere, a portion of the starch is 

 actually separated into carbon and water, the carbon at the moment of sepa- 

 ration uniting with the oxygen, and forming carbonic acid (CO2). This 

 acid is given off into the soil in the form of gas, and thence partially es- 

 capes into the air; but for what immediate purpose it is evolved, or how 

 its formation is connected with the further development of the germ, has 

 not hitherto been explained. 



2°. The formation of acetic acid (vinegar) from the starch of the 

 grain is also easy to com{)rehend. For, as we have already seen, 

 Starch . . . ^Cj^ H Ojo 

 3 of Vinegar ..=Ci^H9 O9 



Diirerence = H, Oi ; or the elements of 



an atom of Valer. Therefore, in this early stage of the growth of the 

 germ a portion of the starch is deprived of the elements of an atom of 

 water, and at the same time transformed into vinegar. 



Why is this vinegar formed? It is almost as difficult to answer this 

 question as to say why carbonic acid is evolved from the seed, though 

 both undoubtedly serve wise and useful ends. 



It has been explained in the preceding lecture how the action of dilute 

 acids gradually changes starch into cane sugar, and the latter intograjje 

 sugar. While it remain's in the sap of the sprouting seed, the vinegar 

 may aid the diastase in transforming the insoluble starch into soluble 

 food for the plant, and may be an instrument in securing the conversion 

 of the cane sugar, which is the first formed, into grape sugar, — since 

 cane sugar cannot long exist in the presence of an acid. 



After the acetic acid is rejected by the plant, it may act as a solvent 

 on the lime and other earthy matters contained in the soil. Liebig sup- 

 poses the especial function of this acid — the reason why it is formed in 

 the germ and excreted into the soil — to be, to dissolve the lime, &c., which 

 the soil contains, and to return into the pores of the njots, bearing in so- 

 lution the earthy substances which the plant requires for its healthy 

 growth. This is by no means an unlikely function. It is only conjec- 

 Tural, however, and since the experiments of Braconnot have shown that 

 acetate of lime, even in small quantity, may be injurious to vegetation, 

 it becomes more doubtful how far the formation of this compound in the 

 soil, and the subsequent conveyance of it into the circulation of the plant, 

 can be regarded as the special purpose for which acetic acid is so gene- 

 rally produced during germination. 



3°. The early sap of the young shoot is sweet ; it contains grape su- 

 gar. This sugar is also derived from the starch of the seed. Being 

 rendered soluble by the diastase formed at the base of the germ, the 

 starch is gradually converted into grape sugar as it ascends. The rela- 

 tion between these two compounds has been already pointed out. 



Starch =Ci2HioOxo 



Grape Sugar . . . =^^12^x2^12 



Difference . . , . = H2 O2; or the ele- 



ments of two atoms of water. The water which is imbibed by the seed 



