CHEMICAL TRANSFORMATIONS. 



95 



constituents of water ; others are produced 

 in consequence of a further disunion of 

 those first formed. The urea and carbonate 

 of ammonia are generated by the combina- 

 tion of two of the products, and in their for- 

 mation the whole of the elements have as- 

 sisted. 



These examples show, that the results of 

 decomposition by fermentation or putrefac- 

 tion comprehend very different phenomena. 

 The first kind of transformation is, the 

 transposition of the elements of one complex 

 compound, by which new compounds are 

 produced \yJlfLQr without the assistance of 

 the elements of water. In the products 

 newly formed in this manner, either the 

 same proportions of those component parts 

 which were contained in the matter before 

 transformation, are found, or with them, an 

 excess, consisting of the constituents of wa- 

 ter which had assisted in promoting the dis- 

 union of the elements. 



The second kind of transformation con- 

 sists of the transpositions of the atoms of 

 two or more complex compounds, by which 

 the elements of both arrange themselves 

 mutually into new products, with or with- 

 out the co-operation of the elements of wa- 

 ter. In this kind of transformations, the 

 new products contain the sum of the con- 

 stituents of all the compounds which had 

 taken a part in the decomposition. 



The first of these two modes of decom- 

 position is that designated fermentation, the 

 second putrefaction ; and when these terms 

 are used in the following pages, it will 

 always be to distinguish the two processes 

 above described, which are so different in 

 their results. 



CHAPTER V. 



FERMENTATION OF SUGAR. 



THE peculiar decomposition which sugar 

 suffers may be viewed as a type of all the 

 transformations designated fermentation.* 



Thenard obtained from 100 grammes of 

 cane-sugar 0.5262 of absolute alcohol. 100 

 parts of sugar from the cane yield, there- 



: I'/* When yeast is 

 water, and I cubic c 

 Produced into agrad 



made into a thin paste with 

 cubic centimetre of this mixture in- 

 . graduated glass receiver filled with 

 mercury, in which are already 19 grammes of a 

 solution of cane sugar, containing 1 gramme of 

 pure solid sugar ; it is found after the mixture has 

 been exposed for 24 hours to a temperature of 

 from 20 to 25 C. (6877 F.,) that a volume of 

 carbonic acid has been formed, which, at 0* C. 

 (32 F.) and an atmospheric pressure indicated by 

 0.76 metre Bar. would be from 245 to 250 cubic 

 centimetres. But to this quantity we must add 11 

 cubic centimetres of carbonic acid, with which 

 the 11 grammes of liquid would be saturated, so 

 that in all 255 259 cubic centimetres of carbonic 

 acid are obtained. This volume of carbonic acid 

 corresponds to from 0.503 to 0.5127 grammes by 

 weight. 



fore, 103.89 parts of carbonic acid and alco- 

 hol. The entire carbon in these products is 

 equal to 42 parts, which is exactly the quan- 

 tity originally contained in the sugar. 



The analysis of sugar from the cane, 

 proves that it contains the elements of car- 

 oonic acid and alcohol, minus 1 atom of 

 water. The alcohol and carbonic acid pro- 

 duced by the fermentation of a certain quan-\ 

 tity of sugar, contain together one equivalent 

 of oxygen and one equivalent of hydrogen, 

 the elements, therefore, of one equivalent 

 of water, more than the sugar contained. 

 The excess of weight in the products is 

 thus explained most satisfactorily ; it is ow- 

 ing, namely, to the elements of water hav- 

 ing taken part in the metamorphosis of the 

 sugar. 



It is known that 1 atom of sugar contains 

 12 equivalents of carbon, both from the 

 proportions in which it unites with bases, 

 and from the composition of saccharic acid 

 the product of its oxidation. Now none of 

 these atoms of carbon are contained in the 

 sugar as carbonic acid, because the whole 

 quantity is obtained as oxalic acid, when 

 sugfir is treated with hypermanganate of 

 potash (Gregory ;) and as oxalic acid is a 

 lower degree of the oxidation of carbon than 

 carbonic acid, it is impossible to conceive 

 that the lower degree should be produced 

 from the higher, by means of one of the 

 most powerful agents of oxidation which 

 we possess. 



It can be also proved, that the hydrogen 

 of the sugar does not exist in it in the form 

 of alcohol, for it is converted into water 

 and a kind of carbonaceous matter, when 

 treated with acids, particularly .with such as 

 contain no oxygen ; and th'is manner of de- 

 composition is never suffered by a com- 

 pound of alcohol. 



Sugar contains, therefore, neither alcohoi 

 nor carbonic acid, so that these bodies must 

 be produced by a different arrangement of its 

 atoms, and by their union with the elements 

 of water. 



In this metamorphosis of sugar, the ele 

 ments of the yeast, by contact with which 

 its fermentation was effected, take no appre- 

 ciable part in the transposition of the ele- 

 ments of the sugar; for in the products 

 resulting from the action, we find no com- 

 ponent part of this substance. 



We may now study the fermentation of 

 a vegetable juice, which contains not only 

 saccharine matter, but also such substances 

 as albumen and gluten. The juices of 

 parsneps, beet-roots, and onions, are well 

 adapted for this purpose. When such a 

 juice is mixed with yeast at common 

 temperatures, it ferments like a solution of 

 sugar. Carbonic acid gas escapes from it 

 with effervescence, and in the liquid, alcohol 

 is found in quantity exactly corresponding 

 to that of the sugar originally contained in 

 the juice. But such a juice undergoes spon- 

 taneous decomposition at a temperature of 

 from 950 to 1040 (35040 CO Gases 



