ABSTRACTS TEACHING METHODS, AIDS, APPARATUS, AND SUGGESTIONS Ifid. A d . Sci., An Efficient Stirrer for Gas Absorption. A. F. BENNING. PIOC. 37, 263 (1927).-"The most convenient way of increasing the rate of absorption of a gas in a liquid is to increase the surface of contact between the two. There are many ways of doing this, hut the most of them are not applicable t o laboratory work. "An ePicient and simple way of increasing this surface of contaft is t o use a stirrer designed to distribute the gas throughout the liquid in the form of fine bubbles, or, better still, atomize the liquid in the presence of the gas. "An easily constructed stirrer for this purpose can be made by sealing two short glass tubes bb' (see Figure) close t o one end of a straight piece of glass tubing a long enough t o serve as a shaft for the stirrer. The end of e below bb' IS just long . enough to reach the liquid when the stirrer is rotated w ~ t hthe arms bb' just free of the surface. The upper end of the shaft a is closed and a small hole is blown in the lower part to permit the entrance of the gas. The junction of the four tubes is constricted so that the crosse section is smallest a t that point, d. "If this stirrerisrotatedwith the arms under the surface, the liquid will flow from the lower tube t o the ends of the arms. Because of the contraction a t the junction and the friction loss a t the liquid entrance, the pressure a t the of the arms is reduced, drawing gas down the shaft f center through the hole c. The liquid and gas are forced out the ends of bb', resulting in the gas being distributed through the liquid in the form of fine bubbles. "If the stirrer is raised so the arms are just free of the surface, gas will be drawn from the hole in the shaft and Ifquid through the,lower tube; the two mI1 he rnt~matelymterrmxed and sprayed throughout the gas space in the containing vessel. This provides an enormous contact surface with a corresponding absorption rate. "In practice this stirrer must he rotated a t a fairly high rate of speed, and to prevent O a THE CONSTR~CTION vibration, or rather to allow the stirrer to align itself, it should he flexibly connected STIRRER with the driving mechanism. This can best a-Shaft; bb'Stirring bearranged by connecting the shaft with the entrance; driving axle by means of a short piece of presc-~as If a mercury seal is used, as is junction; sure tubing. d-Canitricted generally the case, all of its moving parts e8'-Mercury level; f- ~houldbe flexibly connected with the shaft by means of a rubber stopper or similar flexRubber connections. ihle joint. "In one particular case i t was found that a stirrer of this type reduced M. W. G. the time of absorption from 28 t o 3 hours." A Pipet for Measuring Corrosive and Toxic Liquids. Synthetelic Org. Chemicals, Z,2 (Dec., 1928).-"The organic chemist frequently has occasion t o measure out accurately materials like acetyl chloride, acetic anhydride, or phosphorus trichloride which cannot always he weighed easily. A more convenient method of measurement is t o use a pipet, since this avoids exsurfaces of liquid to the air. The attachment shown in the posing diagram has been found'very useful in this connection as a source of suction for the pipet. After a little familiarity with its manipulation, valumetric measurements can be made quickly and accurately using this device. "The parts required are usually available in the laboratory. They pmsjst of a rubber bulb from a storage battery hydrometer, a short
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capillary glass tube fitted with a stopcock, and two rubber stoppers. The accompanying *gram shows the details of assembly, which need little explanation. When ready for use, the pipet is attached and the rubber bulb depressed with the stopcock open. After inserting the point of the pipet into the liquid, the bulb is released and the liquid allowed to rise t o the desired level. When it reaches the calibration mark, the stopcock is turned t o the horizontal position and the pipet removed from the liquid. If normal emptying time is required for accurate measurements, the lower stopper is removed, allowing the liquid t o flow out freely. If a slower outflow is needed. the rubber bulb can be removed and the time of e m.~ .t v i . n gcontrolled bv the stopcock.. "This method of drawing up liquids has been found to he much more satisfactory than using suction from a vacuum line. "By replacing the stopcock described by the usual two-way stopcock, i t becomes unnecessary to detach the pipet in order t o allow the liquid to run out. I t will be possible for the liquid t o drain under its own head by turning the cock so that the pipet is connected with the outside air." G. B. C. Laboratory Hand Grenade Fire Extinguisher. Laboratory, 2, 11 1929) A very m& these, effective fire extinguisher can be cheaply made in any laboratory. take some old electric light bulbs, those with the sealing tip on the top. Immerse the tip under the surface of some CCL in a wide container and with a pair of pliers snap off the glass tip. The evacuated bulb draws in CClr, practically filling itself. The bulb is then placed in an upright position and the tip sealed with litharge and glycerine. The bulb is then a complete fire extinguisher. Several can he placed on a small wooden rack made by drilling a few holes to accommodate the bulb bases. To us-merely "grab" a bulb from the rack and hurl i t directly into the midst of the fire. The bulb breaks, letting loose a flood of CCll in the heart of the flames. G. B. C. A Clamp for Rubber Tubing. H. W. BATCHEI.OR. I d . Eng. Chem., 20, 366 (Aoril. 19281.-"The following method of d a m ~ i n erubber tubine to elass tubing for &e&I labbratory apparatus or for pmssure & vacu;m systems has been found very satisfactory. "A sleeve, approximately l'/* inches (3.8cm.)long may he made of thin glass tubing whose inside diameter is but slightly larger than theoutside diameter of the tub-
ko
;lass and theUmbber tu&& a t b, the latter rs stretched
shown by the heavy lines at d. "When the rubbw tubing has been properly worked
the &eve, the t&o tubes can & easily separated agai; Though not usually necessary, the clamping effect may be increased by slightly widening the end of the glass tubine a t e. "If the clamp is used in the construction of gas-analy'sis apparatus, amercury seal would scarcely b e necessary, since the rubber tube is clamped uniformly throughout its circumference. The clamo mav he modified. however. to form a CUD for a mercurv seal as shown a t f. A m&cu& seal t o connect two rubber tubes can be easily prep&ed by welding a si& arm a t the midpoint of the sleeve. Such a cup can be used either with a straight side arm in a horizontal position or in a vertical position with the side arm bent to a vertical position. "The sleeve alsoafiords an excellen tprotectionfor the rubber tubing if it is necessary to wire it in position on a base as shown. It is hoped to make available in the near fuM. W.G. ture either metal or other tubes for this pumose." A Practical, Inexpensive and ~ u r a b l e~aboraroryEvaporator. P. O m r a ~ . . ('hem I . 2 2 P I I I , I ! -Tlw evnpcntor drscnbrd can bc workcd ~t pressurrs o f 0 2 tuO 2 atmocphvrr, and opcratcd a t nn awmpe tvmpvrature of Xj'c'., the marlmum
temperature attained being 95'C. Thus, the material can be evaporated without spattering. The design of the apparatus is such that little corrosion takes place and the
C ~ o s s S ~ c r Vrsw ro~ TOP VIEW A-Hood; B S h e e t lead bottom; C-Steam inlet valve; D-Steam exhaust; E S e w u outlet pipe, sddered to B; F-Sheet iron bottom and sides (05-2 mm. thickness); G-Wooden supports (10 cm. high'; If-Baked clay slabs, cemented together with a mixture of cement and waterglass; I-Angle iron supports; L-Containers for liquid to be evaporated; K-Covers for openings not in use. solutions being evaporated cannot be contaminated with the product of the corrosion of the bath. For better keeping qualities, the iron parts are painted with asphalt. M. W. G. A New Device in Glass Apparatus. E. I. LEWIS. Chcm. & Ind., 47, 123841 (Nov. 23. 1928).-The author describes and illustrates a device bv which carefullv ground units, similar to the ball and socket type, are held togethe; either by a thin film of lubricant or by a s n e w damp, forming a gas tight but flexible joint. The elements may beglass of different kinds, porcelain or stoneware or other material, but all are mound t o the same curvature so as to be interchanaeahle with units of other material. E. R. W. Safety Tongs for the Laboratory. Laboratory, 2, 5-7 (1929).-Tongs for the convenient handling of beakers, flasks, evaporating dishes, and casseroles have been devised. These safety tongs are offered in sets of four which consist of: Safety Beaker Tong with which any Griffin form beaker having a capacity from 1W ml. t o 1500 ml. can be firmly gripped and safely tipped without danaer of bums from . the hot hraker or snldc from its contents . S ~ t r gF h s k l b n f with rhnch all? I'rlanmeser flask. 123 ml. to I t X X l ml. capacity. ran he Al*o flask- of other shanrs takine" S o.. 4 to -So. -. 10 . rulhrr ~- iafelv handld stoppers grasped with this tong. I t s use enables hot and corrosive liquids t o be poured from flasks without having the liquids drip on the fingers. Sdfdy Utsh Tong with which hot evaporating dibhcs having diameter, from 75 to 120 mm. can he safely handlwl T l ~ euse of thts toug enahlrs the rnntents of n dish tu I*: n~rrrcdwnthwt stnll#na,or thc dlrh can he inverted und thc ~rccioitatcbrushed out Sa~etyCasserole Tong with which hot porcelain casserole; ( ~ & r sSizes No. 1 t o No. 5 indusive) can be safely handled and their contents poured. Each tong is made of Ascaloy, a stainless chromium iron alloy which is rust and chemical resistant. G. B. C. The Bulletin Board as a Teaching Aid. G. P. C ~ n o o ~Sch. . Sci. & Math., 28, 867-73 (Nov., 1928).-A discussion of the prohlem of utilizing the wealth of science material in current periodicals with suggestions for checking and clipping, filing, mounting, titling, grouping, and use of articles of interest and value to science students. R H. -. R. -. Mathematical Problemsin General Chemistry. W. G. B o m n s . Sch. Sci. & Math.,28, 97.580 (Dec, 1928).-Author discusses development of use of problems in chemistry and mndudes that mathematics used in elementary chemistry should: (!),be as simple as possible; (2) deal only with gas volume relations, and reacting quantlt~es; (3) contain enough problems necessary to drive home and make practical each ~
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variety of chemical reaction; (4) be taught t o develop a knowledge of chemistry rather than mathematics. B. H. B. Taking Stock in Chemistry Classes a t Mid-Year. J. 0 . FRANK. Sch. Sci. & Math., 29,3943 (Jan., 1929).-Author advises teachers t o renew and reconsider accomplishments of first semester and evaluate prospects of accomplishing objectives by end of seccnd semester. Accomplishments may he considered under: (1) instruction; (2) inspiration; (3) discipline; (4) power to interpret; (5) explanation and guidance; and (6) recreation. Problem of preventing "let down" in second semester may be met by making work a challenge of student's ability but not discouragingly hard and by introducing new fields of subject matter as fast as the students can understand and assimilate them. Author makes a plea for qualitative analysis as a part of second semester laboratory work. B. H. B. A Method for Using History of Chemistry as a T e a e g Aid. .I. W. WADE. Sch. Sci. b Malh., 28, 877-80 (Nov., 19281.-Author outhnes followmg plan far use of History of Chemistry. At beginning of 2nd semester each student w a s assigned the name of one outstanding chemist and held responsible for information on: (1) life; (2) education; (3) work in chemistry; (4) influence on contemporaries and development of chemistry. Above topics covered by oral report in dassroom and written report a t the end of school year. Chemists were so selected as t o help develop course and pictures, photographs, etc., were collected and used as aids. Author iinds best introduction to an abB. H. B. stract science to be through study of lives of those whose work i t is. The Structure of the Nucleus of the Atom. W. D. WALKER. Sch. Sci. b Math., 28, g36-S(Dec., 1928).-Author submits outline used in course on atomic structure.
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Experiments in Teaching Students How to Study. G. M. WAIPPLE. J. Edm. Res., 19, 1-12 Uan., 192S).-See Chemical Digest, THISJOURNAL, 6, 561 (Mar., 1929). R. M. P. KEEPING UP WITH CHEMISTRY Manufacture of Carbon Dioxide. H. E. H o r n . I d Eng. Chem., 20, 1 0 9 1 4 (Oct., 1928).-A description of the method employed in the new plant of the Dry Ice Corporation, having a capacity of thirty tons per day and believed t o be the largest plant for this purpose in existence. The C02 is produced by burning low sulfur coke, the stack gas containing 16-18 per cent COz. The heat is used t o operate compressors and supply heat needed in the process. The gases are scrubbed with water and the SO2is removed with limestone. The gases pass through absorption towers where the CO. is absorbed hv a 2>/r normal sodium carbonate solution. The orkina1 solution eoniains 7-8 pounds sod& carbonate per cubic foot, and after absorptionthree pounds sodium carbonate and about six of sodium bicarbonate. The residual gas consists of nitrogen and about eight per cent CO. which cannot be recovered economically a t the temperature of the absorption tower which is 120°F. The solution is then led to the boilers where the COz is liberated by boiling a t 240°F. a t a pressure of about eight pounds. The gas is cooled t o remove the water, compressed, and liquefied. On allowing i t t o expand, part of it solidifies, and it is then pressed into blocks and is ready D. C. I,. for the market. Explosive Properties of Solid Hypochlorites. J. WEICAHERZ. Chem.-Ztg., 52, 72930 (1928).-Pure calcium hypochlorite with 70% of available chlorine evolves oxygen slowly a t temperatures below 100". but explodes violently with liberation of its oxygen content a t l l Z O . Mixtures of the hypochlorite with organic substances such as alcohol, tars, mineral oils, or starch are stable a t ordinary temperatures, but, on warming, deflagrate, sometimes with explosive violence. Similar effects are obtained by contact with moisture, but in this case there is a more or less lengthy period of induction M. W. G. depending on the nature of the organic substance. Industrial Mold Fermentations. 0 . E. MAY. Hexagon of Alpha Chi Sigma, 19, 125-30 (Dec., 1928).-During the war. when little attention was paid t o casts, several fermentations were developed and put into industrial operation. More recently fungi seem t o offer industrial possibilities. Their use in the manufacture of cheese, soy sauce, certain beverages, and their action in the disintegration of organic dChris have long been appreciated. Certain different fungi acting on sugar solutions under different conditions produce citric, axalic, formic, gluconic, malic, succinic, acetic, and other acids; also alcohol, cholesterol, fats, and various pigments. Certain fungi are capable of transforming carbohydrates into ethyl alcohol until the concentration is
about 25 per cent, and a French company ir reportcd to be producing alwhol hy mold fermentation. The chief dificulty lies in prrventing infection by other organisms as it flmctions at a bu of 7.11. The most ~ r o m i r i n rfield aoordrs to hr in the nruductron of ormnic acids, which can be produced i t high H-ion cohientrations where-few yeasts and Ixicteria can survive. Citric acid is ~mA&edcommercially from sucrose. requiring about ten days. Almut 170 dilTermt w a i n s of fungi have been mwrrigated hy the Deuartment of Azrm~ltureand a mrthocl for the oroduction of vlucunic acid hai heen deGeloped. It isubelieved by many investigatorsthat a process involving double fermentation will be successful in converting cellulose into alcohol for power purposes, first inoculating with a fungus t o hydrolyze the cellulose and then fermenting these products. D. C. L. Chemical Preoarations for War. Recent Promess in the ADDLications of Chemistrv to the Art of Deitructlon. A. LAVOULE. (From Revue der iiiuanls, Paris.) ~ i v & Age, 335, 244-7 (Dec., 1928).-The author thinks t h a t "intensive work is now being sham. carried hv~the ereat nations of the earth so that the n u t war mav he short. - - - on ~~~ ~ - ~ -.-~ ~ --=, - ~ and characterized b y unprecedented destructiveness." T. B. D. for Thermometers and New Wells. Tycos, 19, 31 (Jan.. 1929).-Apparatus rwording ground tempersturcs as an aid in dctcrminin~the lvcat~onof p;&pective oil wclls hat I I C L . ~ developed by A . J Carlson, petrolemn engineer, a t thc Z'nivrrzity ul California The temperature in we119 over reservoirs of otl increase mom rapidly than in wclls hanen uf o d l%ywatching the raw of increase in temperature durinl: the t i n t few hundred feet. oil well drillers may he saved much cxpen-r am1 trouble in cinking wells. E I.. X4 Symposium on Chemistry and the Food Industries. l a d I.'nq. Chem.. 20, I2XFIS2;r (Drc.. 19?9).--The trtlcs inrludrd are: Chemisrrs nnd the Canning I ~ h s t r y . \ V I). Blgelon-. 11'5~;-9; Chrmistry and the Heveragr Industry. I : . > I . Boylrq. 1%9 92; Chcmiwy and the Bakmg Indostry, C. I( r i - 1 ; Chemistry and the Cwoa and Chocolate Industry, I:. C. Cephan. 12'15-7, Chemistry and the Prrirrvr. or lam and Tell,. Industm. C 1'. I.athrun. 1298-.Wl: Relation of Chcmirtrv to the citrus products industry, C. P. Wilson, 1302-7; Cbe&stry and the FlavorinaExtract Industry, 1%.H Smith. 130; q ; Chcmlstr) und the Shonening Inrlurtry, .\I B. Craff, l:lcl9-1!?: Chemistry nnll the Dairy Industry. (;. E. Ilolm, 1312-5. Kdatiun of Chemi s t to ~ the S1,ice Industrv. 1. Glassford. 1316 7: Chrmistrv and the Breakfast-Fond chemisiry and Food ~egulation,P. B. Dunhar, 1320~ n d u s t r yW. , S. Hilpert, I&%; 2; The Service of Chemistry t o t h e Milling Industry, C. 0. Swansan, 13224; Research in t h e Confectionery Industry, H. S. Paine, 1325-7. These articles are accompanied by illustrations and valuable bibliographies. ~~
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