The Baro-Buret-A
New Accurate Gas Buret'
Harold S i m m o n s Booth ITORLEY CIiE\lIC.\L. ~ . . A B O R i l ' O R > ~ .\ r E S T E R \ .
There i s described t h e construction and use of a new The l i a r o h r e t to hc clcgas b u r e t , t h e baro-buret, i n w h i c h t h e b u r e t becomes tempts to improre the s c r i b e d eliminate> all thest. the well of a barometer, thus enabling t h e experimenter gas buret since its indifficulties. t o read both pressure and volume simultaneously w i t h ception. The chief improveObviously tlic caliief diffigreatly increased accuracy and speed. Since w i t h this iiients haye heeii the derelopculty lie- in the establishiitriit i n s t r u m e n t t h e volume m a y be m e a s u r e d a t a n y deinelit, of devicps of one sort arid maintenancr of tlie Torisired pressure, t h e accuracy of reading s m a l l volumes is or another to cornpelisate for celliari vacuum in thc ti arc^especially increased. t e m p e r a t u r e and pressure m e t r i c column. T h e coniT h e errors and limitations are discussed, including errors, of which that develb i n a t i o n of the o~-erflonoped by W i i t e i l I ) is one of the m a x i m u m error possible u n d e r the m o s t favorable method first applied in tliv the best. conditions for m i n i m u m error. Toepler p u m p arid later t o The sources of errors ill tlie The combination of t h e measurement of pressure t 11e I] a r o rrie t e r del-isetl 11)gas buret are fairly obvious: and volume i n o n e instrument o p e n s u p m a n y a p Germanri (;), with tlie gaplications, s o m e of which are given. buret offered 110 s p i t) ili t ie- . (1) The m e a s u r e m e n t of The practical del-elopinelit pressure by balancing the mercury column against the atmosphere and by reading the pressure of thi. idea iwulted i i i tlie "baro-buret," l ~ h i c l ihas l)eeti of the atmosphere separately on the barometer increases enor- found to he. not only accurate, but also rapid and capahlr mously the errors in pressure reading. of n-ide application. It has been thoroughly tested in this (2) Accurate adjustment of the mercury levels in reading laboratory for seveii years and has heeii applied to iiiitiieroii': the volume is fraught with difficulty. ( 3 ) Accurate temperature control is impractical. prl)blelns sllcc~ssi'ully. (4) Leaks in the rubber connections and leaking of gas into the buret through the rubher tubing connecting the biiret to Design the level tube is a hidden source of error. The I)aru-lliirc~t cousists essentially of two h i l l s : the 100( 5 ) The experimenter is limited to the measurement of the gases a t atmospheric pressure or else may espect serious errors (T. calibrated gas Iiuret, K . and the barometric coliiiiiti. due t o leaks. K . made of glass tubing of the $ a i m hure as the liuret, so that ( 6 ) The use of a compensator introduces errors due to the tlie clepressioii of the mercury due to surface tension dial1 compensator. In the n'hite volume of gas imprisoned in the be the satiie in both tubes. (Figures 1 and 3) These t n o buret, however, this error is minimized part? are coiiiiected by the F t O p c f J C k S .If and -1-by fusedOf these tlifficultieb the first two are probatily tlic iiici>t glass coiiiiectioiis. and through preswre rubber tuhiiig t o serious. t h e nierciiry re>ervoir, R. The tube coniposing the t r a p Several years ago it occurred to tlie writer that tliesr difficiil- L . s h o u l d slope dightly towards tlie I)uret s:) tliat gas I)iilil)lc> ties might he eliiiiinated by an arrangement wheretiy the leaking tlirougli the rubber tuhing nil1 c*)llrct in the trap pressure of the gas in the buret was lialanced liy the prewiirc rather than go up the side tube.. of a colunin of mercury oiilys rather than by tlie pressuw At first it was feared that there wdd he sufficient sti,aiti of the atniospliere. 111 other words. tlir gas lxiret corild to Iircak fused coiinections tietveen the part> of the h i r e t . Iir made the well of a harometer. There have been m w a l aiitl cwiiiectioiis of rubher tubing were used Iietnceti s t q i efforts t o arcomplisli this, hiit they have all resulted it1 clutiisy. rocks .I1 aiid and the trap Id. It xv complicated apparatus. difficult to make and to iiiaiiitaiti. leaked in through the best of tithiiig Oiie of the. earliest of these wa:, del-ked by Fraiiklatid aiitl apparatus. firiiily .-upported and thrii f u s x l together i i i poWard ((;), BIore receiitly I3oue and Kheeler 2, .j) tiiodified -ition. would iiot Iireak, .If a d A\-are large hollo~\--l)lowti Franklaiitl'h buret but liniited it-: usefulne-:s. 13oiic :md
