April 15, 1930
I S D I ' S T R I A L A S D ESGI.YEERISG CHEMISTRY
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Convenient Reflux Regulator for Laboratory Stills' Johannes H . Bruun? BLREXL OF S T ~ Y D A R O S I T
OR a continuous distillation it has been show11 ( 2 )
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theorebically that the reflux ratio (mols of vapor returned as refluxed liquid to the column per unit time divided by the mols of final product obtained per unit time) inust always be maintained above a certain minimum value. in order to obtain a certain degree of fractionation. The theoretical calculation is a more difficult one for the ordinary laboratory rectifying still (batch still) in which the composition of the liquid in the different parts of the tinually changing during the distillation. However, it is generally agreed that a high efficiency of separation is obtained hp using a large reflux ratio and a s i n a l l rate of distillation (.?). rl-
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111order to obtain a definite aiid constant reflux ratio, tlir capillary tubes R and D are made of the same bore but their lengths are made indirectly proportional to the aniouiits of liquid they should carry. For instance, if R = 5 and D = 50, the volume of reflux returned to the column divided hy thc volume of distillate will be 10. Instead of iiiaking the capillary tubes R and D of the same bore hut of different lengtlis;. it may he preferred to have capillaries of different bores b u t of nearly the same lengths. I n order to ohtain the right lengths of the two different, sizes of capillary tubes, these arp sealed horizontally to a vertical glass tube. Liquid is then allowed to run through the T-t'ube aiid the flow per unit tiinr is measured for both capillaries. The capillary tube.; are then gradually shorteried until the desired amount of liquid per unit time n-ill run through each of them. The T-tuhe is then sealed into the system and,recalihrat,ed. This regulator will maintain a definite and constant refliix ratio at any rate of distillation. Hovever, flexibility in thr reflux ratio during a distillat'ion can be accomplished by placing an electric heating coil around the capillary tube: D, thus increasing the flow through D by decreasing the viscosity of the liquid. This device is also a convenient indicator of the rate of distillation, since this rate is directly proportional to the height of the liquid in the bulb C. This bulb may therefore he pro&led with a 1-ertical scale on which each mark corresl)onds to a definite rate of distillation.
Figure 1-Reflux Regulator for Maintaining a Definite a n d Constant Reflux Ratio
For the purpose of controlling the reflux ratio and intlicatirig the rate of distillation, the following reflux regulators ha\-e been found very convenient. They are modifications of a type which is used on industrial stills a i d they give a reflux ratio that is independent of the rate of distillation. For Constant Reflux Ratio
Figure 1 shoivs a reflux regulator for use on stills for which a clefiiiit,e and constant reflux ratio is desired. The vapor leaves the rectifying column a t A . By nieaiis of a reflux condenser, B , it is completely condensed into the bulk) C . From the bottom of this bulh a certain part of the condensate is returned to the coluinn through the ,capillary tube, R . 111other part of the condensate passes through the capillar\tube. D! into the cooler, H, aiid to the receiver. 'Received December 30. I D 5 9 Publication approved b y t h e Director of t h e Bureau of Standards. This paper describes a device which has been de\.eloped i n connection with a n investigation on " T h e Separation, Identification, a n d Determination of t h e Chemical Constituents of Commercial Petroleum Fractions." listed a s Project S o . 6 of t h e American Petroleum Institute. Financial assistance in this work has been received f r o m a research f u n d of t h e American Petroleum Institute donated b y John D. Rockefeller. This f u n d is being administered b y t h e institute with t h e cobperation of t h e Central Petroleum Committee of t h e h-ational Research Council. 2 American Petroleum I n s t i t u t e Research Associate.
Figure 2-Reflux
Regulator for a Measurable a n d Variable Reflux Ratio
For Variable Reflux Ratio
Figure 2 s h o w a reflux regulator for measuring and maintaining any desired constant reflux ratio. I t is convenieritly used where liquids of varied character are to be distilled, ant1 also for determining the most, practical reflux ratio in prolilems involving extensix-e distillation. The vapor leaves the rectifying coluinii a t A and is condensed into t,he Iiulb C . X certain amount of the condensate is returned to the columii through a stopcock, R . aiid a capillary flowiiieter. E , whereas another part is carried through the capillary tube, D, to the condenser, H, and to the receiver. The proportion of reflux to distillate may be regulated by adjustment of R! and a quantitative nieasure of the reflux
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may be obtained a t any time by observing the position of the liquid meniscus above E. This flowmeter is easily calibrated for any liquid by turning the 3-way stopcock, G, and collecting and measuring the liquid obtained during a short interTal of time. With a given setting of R the position of the liquid meniscus above E is also a sensitive index of the rate of distillation. The tube which carries the refluxed liquid back into the rectifying column should be surrounded by an electric heating coil, P , in order to raise the liquid to its boiling point. If desired, the capillary tube D may be replaced by a stopcock in order to give somewhat greater flexibility in reflux ratios, but this introduces the disadvantage of Contamination of the distillate by the stopcock lubricant.
T’trl. 2 , S o . 2
I n both devices there is a free and unconstricted passage between the vapor outlet, A , and the condenqer, H . Thus these regulators may be used for vacuum distillations as well as for distillations a t atmospheric pressure. They have been used successfully n i t h bubbling-cap-plate coluinns ( 1 ) as r\-ell as x i t h iron jack-chain columns. Acknowledgment
ricknomledgment is made to B. J. LIair for his helpful WmstionS in d e T e b i n g this device. Literature Cited Bruun, I \ D ElrG CHEM,, Ana, E d , 1, 212 (1929), (2) ~ ~J I \ ~~ . i caE,r., ~ 14, , 492 (IQZZ), a n d literature cited there ( 3 ) Shirk and Montanna, Ibzd , 19, 907 (1927), a n d literature cited there
Determination of Aluminum and Magnesium in Zinc-Base Die-Casting Alloys’ C h a r l e s RI. Craighead P E I S S S I . V . I ~STATE I~ CoI.I,cr,c, ST.ITECOI.I.EC.Z,I’n
S THE course of some
Various m e t h o d s applicable to the s e p a r a t i o n of f u r the separatiull of large w o r k o n zinc-base diea l u m i n u m a n d z i n c in zinc-base d i e - c a s t i n g alloys are quantities of zinc frorii aliimic a s t i n g a l l o y s in the discussed. The m e r c u r y c a t h o d e is suggested as a num, although a separation laboratory of the Aluminum r a p i d and accurate m e t h o d f o r the d e t e r m i n a t i o n of of aluminum from small quana l u m i n u m a n d m a g n e s i u m in z i n c - b a s e d i e - c a s t i n g Company of America, an intities of zinc call be satisfa?alloys, a n d t h e r e s u l t s o b t a i n e d by t h i s m e t h o d are vestigation of various methtorily accomplished by this ods of separation and deterrecorded. method. mination of aluminum and ( 4 ) T h e precipitation of magnesium in the presence of preponderant amounts of zinc zinc as sulfide in a formic acid solution, holding the aluminum and various other alloying elements and impurities was un- in solution with tartaric or citric acid, was discarded after R dertaken. The object of the present work was to find a preliminary trial. Complete precipitation of the zinc is timerapid and accurate method for the determination of aluminum consuming and the filtration is exceedingly slow. ( 5 ) Separation with ammonium chloride according to the and magnesium in these alloys. method of ilrdagh and Bongard ( 1 ) results in the loss of Usual M e t h o d s aluminum hydroxide. A modification of this method was The composition of typical zinc-base alloys is given in tried, using the following procedure: Table I. The determination of aluminum necessitates a grams of alloy were dissolved in 100 cc. of water and separation from zinc. This separation is usually accomplished TO Twenty cc. of concentrated nitric acid, the nitric acid being added by: (1) repeated precipitation of the aluminum by ammonia; in small portions. The solution was evaporated to a sirup, (2) the addition of ammonium carbonate; (3) a basic acetate diluted to 200 cc. and boiled until solution of the salts was comseparation; (4)precipitation of the zinc as sulfide; ( 5 ) the use plete, allowed t o stand several hours, and the precipitate of acid filtered off and washed with 1:9 nitric wid. of ammonium chloride and ammonia; or (6) the method of metastannic The filtrate was electrolyzed overnight for copper and lead. Gooch and Havens. The electrolyte was saturated with hydrogen sulfide and the
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T a b l e I-Composition of T y p i c a l Zinc-Base D i e - C a s t i n g Alloys METAL SAXPLE A SAMPLE B SAMPLE Per cenl Per cenl Per cenl 2.95 2.86 2.82 c u 0.60 0.32 0.03 Pb 0.10 0.29 0.007 Cd 0.58 4.04 4.04 -41 0.00 0.10 0.11 A1g 0.02s 0 os0 0.oso Fe 5 95 0.00 0.00 Sn 89, i ! ) 2 92.31 92.943 Zn (diff )
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(1) The separation of a l u m i n u ~ iand ~ zinc by ineans of ammonia is unsatisfactory, since the alkalinity required would cause the solution of an appreciable quantity of aluminurn hydroxide ( 8 ) . ( 2 ) Separations based upon ammonium carbonate ( 7 ) are not satisfactory. (3) The basic acetate method, with its tedious neutralization, the sometimes uncertain precipitation of aluminum, and the adsorptive nature of the colloidal precipitate, is not suited Received F e b r u a r y 28, 1930 A thesis submitted in partial fulfilm e n t of t h e requirements for t h e degree of master of science in physical chemistry from t h e Graduate School of the PennsjlTania S t a t e College. 1
precipitate of sulfur and sulfides filtered and washed with acid hydrogen sulfide wash. The filtrate was boiled to remove hydrogen sulfide, a small quantity of bromine water added if necessary, cooled, and made up to a volume of 500 cc. in a graduated flask. A 50-cc. aliquot of this solution was taken for the determination of aluminum and magnesium. T o the aliquot of this solution 10 cc., of concentrated hydrochloric acid and 20 grams of solid ammonium chloride were added, the solution diluted to 200 cc., brought to a boil, and the aluminum hydroxide precipitated with ammonia according to the method of Blum ( 2 ) . The precipitate was transferred to the original beaker, and dissolved in 10 cc. of concentrated hydrochloric acid and 100 cc. of hot water. The solution was heated to boiling and neutralized as before. A third precipitation was made in the same manner and the hydroxide precipitate filtered, dried, and burned off a t 500” C., and then ignited for 1 hour a t 1100” C . . cooled, and weighed. The combined filtrates were evaporated in acid solution t o 200 cc. and the magnesium was determined as phosphate by a double precipitation.
The results of this procedure on a series of nine alloys were invariably high and zinc was present in sufficient amount to account for the errors in thel determination of aluminurn. Several samples were precipitated as before, 5 cc. excess am-
