CHEMISTRY AND INDUSTRY
1U3D
inakcrs iirc sufficient to sliom thnt the vnciiiini drying plaiit is iisiiitlly superior to any forni of nir-drying plant.
This clinpter is such n fsrrngo of iionscnsc that onc is conipellcd to wondcr wlictiicr tlic author Iins cvcr seen a vacuum drying plant. hppnrcntly Iic docs not iintlerstnnd tlie uiitlcrlying principles of tlic system nv a ~-Iiolc, tlic csnct piirposc ol tlic contlcnscr, or of the vacuum puinp.
A p t from thcsc faults, the book inny 1)c consiclercd ns n uscful oiic in tlic liaiitls of tliosc who linve siifficicnt espcricncc so tliiit t h y cannot bc Icd by tlic nose. Tlie dcscription of tlic grnpliical mcthotls of calculation and thc tlingmins arc ivcll worth tlic pricc cliargctl for the book, but tlic stutlcnt must not cspcct to find any practical data of rcnl valuc in tlic design of plant. Xost theoretical books on drying, ho~scvcr, fnll short in this respect; they deal with tlic hygroiiietry of the drying plunt, and i t is uiifortiinatc thnt the authors do not takc the trouble to tcst tho mctliods of ctilculation thcy have so laboriously dcvclopctl upon t.lic actual rcsults obtained froni a few dilfcrcnt types of dryiug plant. If this wcrc donc we shoiild rill bc spared tlic cxpcriencc of wading through tcdions cnlculntioiis which, wliilst t h y niay bc an escellint iiwntnl disciplinc aiitl scrvc to sliarpcn our critical powrs, do not put us in tlic position systcniaticnlly to develop thc design of drying plant froni pliysicnl principles.
.iZcyscIicr had a n escclleiit opportunity : lic started with a nietliotl of calculation which relieves thc subjcct of niaiiy of its tedious fciitures, and if Iic lintl applied tlic yardstick of practical cxpcricncc to his calciilatrtl conclusions Iic ivoultl liavc avoitlcd the scrious niist:ikcs wliicli liuvc rcntlcrctl his book a clangcr to chcniical cngiiiecring education rather tlinn n m i l hclp.