the wet coiiihustimt I iiiiiiat,ioii. 'L'lie rcsiilts, gir.en in 'ralile I, especially tli 'or nitrogen, itre in g,wd general ztgreement,,and indicate that rrlicrc OLIO wishcs to determine carbon rind nitmgcn on the same soil snsiiples the suggestion ollercd will prom con\-ciiicnt. l h h l e I --Total Carhon INonide and NiCro4en hy T w o Method8
Merviiric, oxide iind miiiig:ui~w perwide were also t.ried jilncc of chroinic acid, but in bot,li es the resulk iverc lower tliiiri wit11 clirumic :acid. 0xyge11 gas was passed ill
tlirnugh the inisturc iii ccrtiiiii trials, the main advantage in its use liciiig that the temperatiire coold he raised more quickly owing to iihctter regulation of tlic pressure. In a iiumbcr of inst,aiices where nitrogen deterrriiiiatioiis were made in the u,siinl way, usiiig mangniicse peroxide ill varyiiig amounts mil employing different durations of time in digestion, it >viis foiuid tiiitt digestion of tlie soils with mangaiiese peroxide nod sulfuric acid, followxl by distillation witli dkali, g a x a greater :niiouiit of nitrogen than the Gullllillg 1nethod. Summarq
The ri!snlts 0bt2~iii0dinilicrite that cz~rbonitiid nitrugen can be deteriiiined fairly aecorately on the same soil sample by the wet combust,ioii mctlrod. Aft.er oxidizing the carbonaceous matter the residue nray be employed direct for the &termination of nitrogen in tlie iisiid way. Although t,he carbon results, exprersrxl as carbon dioxide, were lower by the wet combustion method than by the funiace method, the nitrogen was conipletely changed to ammonium sulfate without loss diiring oxidation. Mercuric oxide or manganese peroxide, when substituted for chromic acid, gave lower results. The results obtained for nitrogen, wtlen iriariganese peroxide and sulfuric acid were used, ran higher than did those obtained with the Gunning method.
Portable Laboratory Bench Units' A R T I ~ KD LITTLR, Irr., C a m a m x ~ a .MASS.
SPECIAL problem is presented by the use of smallA scale comniercid apparatus in the research laboratory where the type of work is varied and cannot be predicted in advancc. Such apparatus innst be readily available, easily supplied witli stemx, gas, cornprcsscd air, or electricity and, while ample working space must be provided during a series of experiments, such space in t not be wasted vhen the equipment is idle over any appre Llc period of time. In this laboratory this pruhlem lins t.mw mot, hjy the CUIIstruction of port,able bench units, each u n i t coinprisiiig it set of related equipment, arid supplied rvitli it fractionnl horsepower motor, transmission belting, gears, &., as well :as tlic necessary piping atid wiring. A special hood had been constnmted which may he used with any of the benches, and only oiic liood is required, siiice it is seldoni that two or more of tlie benches arc in use simultaneoinly on work which requires the removal of fumes, smoke, or odors. A typical unit, shown in the illustration, inr:liidcs iiiixiog nnd grinding apparatus-a sniall mixer, gas heat,ed, a paint mill, and a double pon:elain-jar ball mill. These pieces of apperatus are belted to a small countershaft, driven tlmiiigli a high-ratio reduction gear which permits the use of an iiiexpensive, higli-speed motor. The benches are coiistrricteil of l'/Anch angle iron, braced with 1-inch strap iron, They are provided with cast,ors aiid are therefore easily inoved about. The over-all dimensions arc 30 bv 42 Lv 37'/,, inches high. The use of unit benches bas uartiallv solved tlic iiiiiiuviilie problem of storage of small-scale equipment, wed For comparatively brief periods at irregular intervals. The appara-
, Received Feliiuaiy 28. 1!127.
tils is easily kept in good i:onditiiin and is always ready for immediate use, in any of the rooms of t,he laboratory. Although tlie first of the benches was made oiily a few months ago, they have already repaid their cost many times over and have been isi action on a wide variety of experimental work.
