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LXIV. On the Preparation of Artificial Yeast. By George 

 Fownes, Ph.D.* 



TT often becomes a matter of great practical importance to 

 -*■ have it in our power to excite the vinous fermentation under 

 circumstances in which ordinary yeast cannot be obtained. In 

 making bread, for example, although the use of yeast may be 

 avoided by employing what is called "leaven," or dough 

 which has already become sour and partly putrefied by spon- 

 taneous change — a practice which has been followed from the 

 most remote antiquity, and is still occasionally in use — the 

 bread so made is always to be distinguished by a peculiar sour 

 and nauseous taste and smell, and can never bear comparison 

 with that fermented by yeast. 



The object of the present notice is to point out a method 

 by which yeast of the most unexceptionable quality can be 

 artificially produced at will. I am aware that some substitute 

 for ordinary ferment in brewing has long been known to cer- 

 tain persons, who go about the country and impart their secret 

 to those who are willing to purchase it : of the nature of this 

 preparation I am ignorant, and a reference to systematic che- 

 mical works will suffice to show, that whatever it be it has 

 never been made public. 



On turning to Berzelius, it will be found stated f, that 

 although the reproduction, as it were, of yeast, the conversion 

 of a small into a large quantity, is a very easy thing, yet to 

 produce that substance from the beginning is very difficult. 

 He describes a process for this purpose on the authority of 

 Dr. Henry, and which consists in taking a strong infusion of 

 malt, saturating it with carbonic acid, and then exposing it 

 for some days to the proper fermenting temperature, when a 

 small quantity of yeast is gradually formed and deposited, 

 which may, by various contrivances, be made to give origin 

 to a larger. I shall have occasion to notice presently the be- 

 haviour of a malt infusion when left to itself at a temp, of 70° or 

 80° F. for some time, and to show that the addition of carbonic 

 acid is wholly unnecessary. 



The principle of induced chemical action, which Liebig has 

 assumed to explain a great number of those extraordinary 

 phaenomena to which Berzelius gave the term " Catalysis J," 

 and which principle has been so fully confirmed, and even, 

 perhaps, extended by the late valuable researches of MM. 



* Communicated by the Chemical Society, having been read March 15, 

 1842. 



•f* Lehrbuch, vol. viii.89. foot note, third edition. 

 [J See Phil. Mag., S. 3. vol. x. p. 490.—Edit.] 



