A

cxxn

Elements of Pharmacy.

Part I.

•

]

IV. 1 *

I

perry; and an infusion of malt, which, when fermented withyeast, forms beer. The briskness and sparkling of some ofthese liquors depend on their being put into close vessels be-fore the fermentation is completed, by which means a portionof carbonic acid gas is retained.

596. The acetous fermentation. —All vinous liquors are sus-ceptible of the acetous fermentation, provided they be exposedto the action of the atmosphere, in a temperature not less than70". An intestine motion and hissing noise sensibly takeplace in the fluid ; it becomes turbid, with filaments floating init, and its temperature increases ; it exhales a pungent acidsmell, without any disengagement of carbonic acid gas. Gra-dually these phenomena cease ; the temperature decreases,the motion subsides, and the liquor becomes clear, having de-posited a sediment and red glairy matter, which adheres tothe sides of the vessel. During this process, the alcohol andmalic acid disappear entirely, oxygen is absorbed, and acetousacid formed.

597 • The panary and colouring fermentation —is less under-stood than those already described, A paste of wheat-flourand water, exposed to a temperature of 65", swells, emits asmall quantity of gas, and acquires new properties. The glu-ten disappears, and the paste acquires a sour disagreeable taste.If a just propoition of this fermented paste or leaven, or, whatis still better, if some barm, be formed into a paste with wheat-flour and water, the same fermentation is excited, without thedisagreeable taste being produced ; the gas evolved is prevent-ed from escaping by the viscidity of the paste, which thereforeswells, and if baked, forms light spongy bread.

598. The putrefactive fermentation ___Although vegetable

substances, when they are destroyed by spontaneous decompo-sition, are said to putrefy, we shall consider this fermentationas belonging exclusively to animal substances, oi those whichcontain nitrogen as an elementary principle. The essentialconditions oi puti'efaction are humidity, and a temperature be-tween ^'^ and 110°. The presence of air, the diminution ofpressure, and the addition "of ferments, are not essential, butaccelerate its progress. The smell is at first vapid and dis-agreeable, but afterwards insupportably fetid, although the fe-tor lor a time, is somewhat diminished by the mixture of anammoniacal odour. Liquids become turbid and flocculent.Soft substances melt down into a gelatinous mass, in whichthere is a kind of g> ntie motion and swelling up, from the slowand scanty formation of elastic fluids. Solids, beside the ge-neral solteniug, exude a serosity of various colours, and by de-