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ACETIC ACID.— Malt Vinegar.

When the malt is crushed or ground, it fallsthrough a hose or trunk into the mash-tuns in thefloor beneath. These mash-tuns are similar to thoseused at large breweries and distilleries, but smaller insize. They are circular vessels, with a central stirrer,or instrument for keeping in constant agitation theingredients contained in the tuns—the stirrer beingworked by a steam-engine. It is in these vesselsthat the saccharinefermentation proceeds. The diastase,which is very soluble, acts upon the unaltered starchof the grain, and converts it into dextrin and grapesugar, as before mentioned. This grape sugar(sometimes also called glucose, dextrose, and mal-tose) is the sweet principle which subsequentlyyields to the brewer his beer, to the distiller hisspirit, and to the vinegar-maker his acetic acid;and it may well be supposed that every precaution istaken, and every investigation made, as to the ex-Rlff- 4.

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traction of the greatest quantity and the most fittingquality of this important agent. The quantity ofwater required for a given quantity of malt, and thetemperature at which the water is used, vary in eachparticular branch of manufacture, according to thestrength of the wort required. The arrangementsfor settling these are very exact and ingenious.Ilot water is let down upon the malt in the mash-tun when at the proper temperature ; and in orderto adjust this the foreman of the brewhouse ascer-tains, by the aid of a thermometer, the temperatureof the water through a temporary opening in theupper part of the boiler. This is shown in Fig. 4,where is also represented a balance-weight andgraduated scale, which, aided by a float on the sur-face of the liquid in the copper, indicates the depthof the water.

When the water has acted on the malt for a certain

period, and been constantly stirred with it, the liquorreceives the name of wort, and is allowed to flowthrough pipes out of the mash-tuns into a largecast-iron tank, or underbade, measuring 24 feetor upwards in length, by 8 in width. This ismerely a general receptacle for the wort, into whichthe latter is collected when the mashing is completed.Cooling is effected by various mechanical contrivances,which differ very greatly in different establishments.Large, open, shallow, airy rooms, called coolers, orcooling-floors, in which a thin layer of wort was cooledby the access of air on all sides, was the mode for-merly adopted. This plan has, however, beensuperseded by contrivances, in which 100 squarefeet of surface is made to abstract as much heat as■was formerly done by twenty times its extent. Oneof the refrigerators employed acts in the followingway:—The hot wort is allowed to flow out of theunderback into an oblong vessel, and out of this

Fig. 5,

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into another receptacle in the same part of thebuilding. A continuous pipe, between 300 and 400feet in length, passes backwards and forwards throughthe oblong vessel, and through this pipe cold waterflows incessantly from an Artesian well 200 feet indepth. Constant currents of wort run in one direc-tion through the apparatus, while a current of waterin an opposite direction flows through the pipe whichcools the wort.

The temperature of the wort may be cooled evento that of the water were it required, either byincreasing its influx and retarding its efflux, or bypermitting a larger quantity of water to flow throughthe pipe. The proper temperature is attained byregulating the relative streams of wort and waterby suitably adjusted valves. Fig. 5 represents therefrigerator at the end where the wort enters, andwhere the water leaves the pipe, after having per-formed its office ; collateral with the refrigerator isthe under back. Not only does this method require