346 FERMENTATION 



wise in butyric and in urea fermentation (conversion of the urea into a carbonate of 

 ammonia). 



Opposed to this view Schubert has published an investigation upon yeast. In order 

 to prove that the action of yeast is due merely to its porosity, he founds his invest i#i- 

 tion upon some experiments of Brendocko (particularly in reference to the statnm nt, 

 that fermentation taking place in a solution of sugar in contact with porous bodies is 

 duo to an impurity of sugar) ; according to which various porous bodies, such as char- 

 coal, paper, flowers of sulphur, &c., to which some bitartrate of ammonia is aiMrd, 

 are capable of inducing 1'ermontation in a solution of raw sugar. His observations 

 are also based upon some experiments of his own, which seem to indicate that porous 

 bodies, even without the addition of a salt, are capable of exciting fermentation in a 

 solution of (pure?) cane-sugar. Whatever may be the means whereby alcoholic IVi-- 

 montation is induced, he states it to bo indispensable that the body in question should 

 bo exposed for some time to the influence of air, and that oxygon and carbonic acid 

 are absorbed by the ferment. Both oxygen and carbonic acid, being oloctro-negativo 

 substances, stand in opposition to the electro-positive alcohol, and therefore pxedispOBQ 

 its formation, but only when they are highly condensed by the powerful surf ace -at trac- 

 tion of the yeast, or of any porous body. The -electrical tension, ho states, m;iy l>o 

 increased by many salts, provided that the latter do not at the same time chemically 

 affect either the sugar or the ferment. 



C. Schmidt has communicated the results of his experiments to the ' Annal. 

 Chem. Pharm.' After stating numerous experiments, he continues : ' Nor are fungi 

 the primum movens of saccharine fermentation ; the clear filtrate obtained by throwing 

 almonds crushed in water upon a moist filter, soon induces fermentation in a solution 

 of urea and of grape-sugar ; in the latter case, no trace of ferment-cells can be dis- 

 covered under the microscope, not oven after fermentation is fully developed. If the 

 solution, still containing sugar, is allowed to stand eight days or a fortnight after 

 fermentation has ceased, an exuberant development of cellular aggregations is ob- 

 served, but no putrefaction ensues ; the fungi, well washed and introduced into a 

 fresh solution of grape-sugar, continue to grow luxuriantly, inducing, however, if at 

 all, but very weak fermentation, which rapidly ceases ; hence the growth of fungi 

 during fermentative processes is but a secondary phenomenon. The increase of the 

 residuary ferment, which occurs after yeast has been in contact with sugar, arises 

 from a development of ferment cellulose, which probably takes place at the expense 

 of the sugar. If muscle, gelatine, yeast, &c., in a very advanced state of putrid do- 

 composition be introduced into a solution of 1 sugar in 4 water, all phenomena of 

 putrefaction disappear; after a few 'hours, active fermentation sets in, ferment-cells 

 being formed, and the liquid contains alcohol, but no mannite. The inactivity of 

 crushed yeast is duo, not to the destruction of the fungi, but to the chemical changes 

 which are induced in yeast during the considerable time necessary for complete com- 

 minution. The crushed cells, introduced into sugar-water, give rise to tho produc- 

 tion of lactic acid, without evolution of gas.' Schmidt is of opinion that fermentation 

 is a process analogous to the formation of other. He believes that one of tho con- 

 stituents of yeast, together with the elements of grape-sugar, gives rise to tho forma- 

 tion of one or several compounds, which are decomposed in statu nascenti (like 

 sulpho-vinic acid), splitting into alcohol and carbonic acid. 



Wo believe that tho preceding paragraphs fairly represent tho views which have boon 

 promulgated upon tho phenomena of change, which are in many respects analogous 

 to those of combustion and of vitality, presented in the fermentative processes. 

 Much has been done, but there are still some points which demand tho careful at- 

 tention of tho chemist. 



In a practical point of view, tho question which arises from tho alteration in tho 

 specific gravity of tho fluid by fermentation is a very important one, a knowledge 

 of tho original gravity of beer being required to fix tho drawback allowed upon 

 beer when exported, according to the terms of 10 Viet. c. 5. By this act a drawback 

 is granted of 5s. per barrel of thirty-six gallons upon beer exported, of which ' tho 

 worts used before fermentation wore not of less specific gravity than T054, and not 

 greater specific gravity than 1'081,' and a drawback of 7*. 6d. per barrel upon boor 

 of which 'the worts used before fermentation wore not of less specific gravity than 

 T081.' Tho brewer observes the original gravity of his worts by moans of some 

 form of the hydrometer, and preserves a record of his observation. Tho revenue 

 officer has only tho beer, from which lie has to infer the original gravity. From 

 tho great uncertainty which appeared to attend this question, Professors Graham, 

 Hofmaun, and Redwood wore employed by tho Board of Inland Revenue to discover 

 how tho original gravity of tho beer might bo ascertained most accurately from the 

 properties of tho beer itself. When worts are fermented, the sugar passes into 

 alcohol, and they lose in density, and assume as beer a different specific gravity. 



