Issued August 18, I'JOO. United States Department of Agriculture, BUREAU OF CHEMISTRY— Circular No. 44. H. W. WILEY, Chief of Bureau. APPARATUS FOR USE IN THE DETERMINATION OF YOLATILE ACIDS IN WINES AND VINEGARS. By H. C. GOKE, Assistant Chemist, Division of Foods, lu tliis modification of tlie Hortvet-Sellier apparatus « a copper flask is sub- stituted for tlie outer glass flaslv and a constant feed device for the flask has been added ; there are also two changes of a minor nature consisting in a small ridge blown in the inner flask to form a shoulder for the rubber gasket and the elimination, as unnecessary, of the dropping funnel. The constant water feed is operated by running the supply water through tube a (fig. 1), which passes through tube &. The overflow passes through h and rises through tube c to the small basin d, which is connected with the drain. Tube a is placed within tube ?', because steam is so prevented from passing out through 1). Distilled water should be used which has been largely freed from carbon dioxid by washing it from twenty to thirty minutes with a rapid stream of air. The water should be admitted somewhat more rapidly than it is used. The rate of flow is con- veniently regulated by comparing the rate of drip in the small sight tube e with that from the condenser. Experiments with the. apparatus showed that when tap water was supplied to the generator there was an error due to the presence of carbon dioxid in the distillate, equal to about 0.3 cc of tenth-normal alkali in 100 cc, phenolphthalein being used as indicator. When ordinary distilled water was used, the error was about 0.15 cc. When distilled water was employed from which the greater portion of carbon dioxid had been removed by aerating, the error was but 0.05 cc. The error is constant and may be subtracted from each determination. The apparatus is operated as follows: Place 10 cc of the sample in the inner flask, which should have been removed from the outer flask and be entirely cool. If the sample is noticeably charged with carbon dioxid, pass through it a current of air for a few minutes by attach- ing to the flask a stopper bearing a glass tube wjiich is connected with suction. « J. Ind. Eng. Chem., 1909, 1 : 31. XMr. 44] 2711—09 * The air passes in through the side tube in the flaslv and washes out practically all of the carbon dioxid in the sample without removing appreciable quantities of volatile acid. Connect the flask with the distilling bulb and place in the outer flask, tube / of the outer flask being open. Make all connections tight and close tube /, In the case of wines, collect about 100 cc of the distillate. In the case of vinegars, from 200 to 300 cc are required. Titrate distillate with stand- ard alkali free from carHlwiates using phenolphthalein as indicator and subtract 0.05 cc for each 300 cc (i^^ distil late. About fifteen minutes are required for a determination of volatile |icid in win^ and from thirty to forty-five minutes in the case of vinegar. The volume of* liquid in the inner flask increases but very slowly during a determination. The apparatus should find a wide use in the determination of volatile constituents. ICir. 44] o Digitized by the Internet Archive in 2007 with funding from IVIicrosoft Corporation http://www.archive.org/details/apparatusforuseiOOgorerich 14 DAY USE RETURN TO DESK FROM WHICH BORROWED LOAN DEPT. This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. lOSep'63Ef SEP T 0 1963 NOV 0 2 1995 qiRCULATION DEPT. —DOE FEB - 8 » SUBjeCT TO RECALL IMMEDIATELY 8EP15'64-5Pi JUN 13 1976 K&CHI. MKriPTS FEB 01 1996 LD 21A-50m-ll,'62 (D32798l0)476B General Library University of California Berkeley 1931 V%'-^r.v:> VC 6S407 CD5mQS