A N A L Y T I C A L EDITION
72
The phosphorus content of the chrome ores usually encountered is so low that the error introduced by its inclusion with the alumina is negligible, except when the highest accuracy is desired. To make correction for chromium, the oxides are fused with 6 to 8 grams of sodium carbonate, the fusion is dissolved in water and filtered, and chromium is determined colorimetrically by comparison with a standard solution of potassium chromate prepared by dissolving 1.867 grams of anhydrous potassium chromate in 1 liter of water (1 cc. = 0.0005 gram Cr). The chromium found, calculated to Cr203, is deducted from the weight of the impure alumina, and the remainder is calculated to percentage of A1203 in the ore. If desired, phosphorus may be determined in the solution after the estimation of chromium, calculated to P z O ~and , deducted from the alumina. Determination of Lime and Magnesia
The combined ammoniacal filtrates from the iron and aluminum hydroxide precipitates are made slightly acid with hydrochloric acid, evaporated to a volume of approximately 150 cc., and cooled to 15" C. Twenty cubic centimeters of a 10 per cent solution of diammonium phosphate are added and ammonium hydroxide (sp. gr. 0.90) is then slowly introduced, drop by drop, with vigorous stirring until the solution is ammoniacal and a crystalline precipitate appears. Fifteen cubic centimeters of ammonia (sp. gr. 0.90) are added, the liquid is stirred thoroughly and finally chilled by surrounding the beaker with crushed ice. After standing for several hours with frequent stirring, or preferably overnight if allowed t o stand a t room temperature, the solution is filtered on a 9-cm. blue ribbon paper, and the precipitate is washed three or four times by decantation with cold 2.5 per cent ammonia water. Twenty-five cubic centimeters of hydrochloric acid (1:l) are poured through the filter, the filtrate being collected in the original beaker containing the bulk of the precipitate, and the filter is washed thoroughly with 5 per cent hydrochloric acid. The solution is diluted with cold water to a volume of 150 cc., 3 cc. of a 10 per cent solution of diammonium phosphate are added, and the precipitation is repeated as previously described. The precipitate is allowed t o stand for 2 hours surrounded by crushed ice,filtered, washed
Vol. 1, No. 2
ten or twelve times with cold 2.5 per cent ammonia water, and ignited in a weighed platinum crucible, first a t a dull red heat until the carbon has been burned, and finally to constant weight a t 1000-1050" C. The pyrophosphate precipitate thus obtained-which will contain all the lime, magnesia, any manganese present, and small amounts of silica-is dissolved in 20 cc. of hot dilute (1:4) hydrochloric acid, the solution is filtered on a 7-cm. paper to remove silica, and the filter is washed well with hot water. The paper and silica are ignited and the silica determination is completed in the usual manner. The weight of silica found is deducted from the weight of the magnesium pyrophosphate obtained as previously described. Ten cubic centimeters of sulfuric acid (1:l) are added to the filtrate from the silica and the solution is evaporated to fumes of sulfur trioxide. Five cubic centimeters of water and enough absolute alcohol to constitute 90 to 95 per cent of the total volume are added, and the solution is stirred vigorously for several minutes. After the calcium sulfate precipitate has settled for 2 or 3 hours, preferably overnight, it is filtered on a 9-cm. blue ribbon paper and the paper and precipitate are washed free from phosphoric acid with 80 per cent alcohol. The calcium sulfate is dissolved in 25 cc. of hot 10 per cent hydrochloric acid and the solution is heated to boiling. Onetenth gram of oxalic acid is added and the lime is precipitated by the slow addition, with vigorous stirring, of dilute ammonia (1:3) in slight excess, the determination being completed in the usual manner. The weight of calcium oxide found is calculated t o tricalcium phosphate (Ca3(PO&) by multiplication by 1.8447, and this amount is deducted from the weight of the magnesium pyrophosphate obtained as previously described. The alcoholic filtrate from the calcium sulfate is evaporated until strong fumes of sulfur trioxide are evolved and all organic matter is destroyed. After the solution has cooled, the residue is dissolved in 25 cc. of nitric acid (sp. gr. 1.135) and finished for manganese by the bismuthate method. Any manganese found is calculated to manganese pyrophosphate (MnsP207,) (factor, 2.5847), and this is deducted from the weight of magnesium pyrophosphate. The weight of Mg2P207 is multiplied by 0.3621 and by 200 to obtain the percentage of MgO in the sample.
Rapid Dehydration of Alcohol Using Barium Oxide and Metallic Calcium' G. Frederick Smith UNIVERSITY OF ILLINOIS, URBANA,
HE many applications of absolute ethyl alcohol in
T
experimental research and in the operations of quantitative analysis, particularly with the alkali and alkaline-earth metals, make a convenient and rapid method for the dehydration of 92 to 93 per cent ethyl alcohol desirable. No claims to originality are made for this paper. Rather the attempt is made to indicate the serviceability of barium oxide as a rapid and practical alcohol drier. This fact has not been indicated in previous investigations as far as could be learned. Metallic calcium is further advocated for the rapid removal of the last half per cent of water. The bibliography of the literature on alcohol and alcoholometry has been most completely compiled down to a recent date by McKelvy.2 An extensive investigation by 1
Received October 1. 1928. S. Bur. Standards, Bull. 9, 436
* McKelvy, U.
(1913).
ILL.
Osborne, NcKelvy, and Bearc@ on the preparation of pure anhydrous ethyl alcohol, the determination of the thermal expansion of mixtures of ethyl alcohol and water, together with density data for the same aqueous alcohols, accompanies McKelvy's bibliography. General Considerations
The heat of reaction for the hydration of barium oxide is greater than that for calcium oxide. This fact suggests its use in the dehydration of alcohol with resultant increase in the heat and rate of reaction. Formerly the cost of barium oxide as compared with lime in addition to its threefold molecular weight per unit of hydration served as a deterrent 8 Osborne, McKelvy, and Bearce, U . S. Bur. Standards, Bull. 9, 327 (1913).
I
April 15, 1929
INDUSTRIAL A N D ENGINEERING CHEMISTRY
73
to its usee4 Certain known reactions of barium oxide and previously calibrated, and thermostat accurate to 0.01 degree alcohol, to be subsequently tabulated, indicate undesirable a t 25" C. were employed. After temperature equilibrium was characteristics. reached the pycnometer and contents were withdrawn from Absolute alcohol can be prepared from hydrated alcohol a t the thermostat, chilled momentarily, rapidly dried, and placed ordinary temperatures if a sufiriently large excess of lime and in a tared weighing bottle with a thoroughly ground glass extended time intervals are employed. Two such experi- stopper and weighed. From the data thus obtained the ments are given by Crismer5 and the results are presented density of the alcohol corrected to 25O/4' C. was calculated. graphically in Figure 1. Curve I shows the gradual dehydra- The percentage of water present was found from the tables tion of aqueous ethyl alcohol using four times the theoretical given by McKelvy.2 The apparatus employed, the calibraamount of lime while curve I1 gives similar data for nine times tion of weights, pycnometer, and thermometers, vacuum corthe theoretical amount. Even in the second case 21 days were rections, etc., indicated an accuracy of *0.01 per cent in the required to obtain absolute alcohol starting a t 98.75 per cent. water content determined. TREATMENT WITH METALLIC CALcIunr-Since the turnings Curve I11 represents experiments using the theoretical amount of barium oxide with other conditions comparable. Starting were not sufficiently finely divided to present a large surface with 93 per cent ethyl alcoc o m p a r e d with the total hol. 90.61 Der cent alcohol I, ,I weight of metal. a DroDor" was p r o d k c e d in 3 days. tionally large excess of calThe increasing use of practically dry alcohol in The yield of dried alcohol is cium was suspended in the analytical chemistry as well as for a multitude of other much greater than for the boiling alcohol using a wire purposes makes the improvement of the conditions dehydrations using excess of gauze basket. The basket under which it may be produced attractive. This lime. of turnings was suspended paper demonstrates that, from the point of view of The heat of reaction beby a fine wire through the speed, economy, and simplification of manipulation, tween aqueous alcohol and reflux condenser and when barium oxide, which is now obtainable cheaply in any barium oxide can be demonthe reaction was thought quantity, is attractive. Previous objections to its strated i n t h e following complete the excess metallic use for this purpose have been shown to be overmanner: If 200 to 300 cc. c a l c i u m was withdrawn. emphasized and not practicable deterrents to its use. of 92 to 93 per cent ethyl The metal t u r n i n g s a n d The chief objection, that of poor yield, has been shown alcohol a r e p o u r e d over basket were then placed in to be invalid. A discussion of the various chemical twice the theoretical quana well-stoppered bottle and reactions encountered and a further advocation of tity of barium oxide, using used for laterreactions. The metallic calcium as a finishing reagent for complete as container an unsilvered alcohol thus prepared was dehydration has been made and data concerning its Dewar flask provided with a distilled and its water conrate of reaction with alcohol are given. reflux condenser, and the tent determined in the same contents a r e t h o r o u g h l y I' '1 wayas forthedistillateof the preliminary dehydration. mixed and allowed to stand, the heat of reaction mill cause the alcohol to boil and this boilDiscussion of Results ing will continue for approximately 1 hour. The results of several runs which illustrate points in quesThe dehydration of 92 to 93 per cent alcohol is always carried out in two stages. Lime is generally employed for the tion sufficiently are given in Table I. first stage and the conditions are adjusted to produce an al- Table I-Dehydration of 93 Per C e n t Ethyl Alcohol Using B a r i u m Oxide a n d Metallic C a l c i u m cohol of approximately 99.5 per cent strength.6 The "abALCOHOL solute" alcohol thus obtained is further dehydrated to 100 RUN ALCOHOL BaO TEMP. TIME YIELD BY W T . cc. Grams c. Hours CC. per cent with a special dehydrating agent,' metallic calcium % 1000 500 25 72 750 99.61 probably being the most convenient and rapid.8 By the use 2 1000 400 99.40 b. p. E50 1000 b. p. E55 400 99.04 11/2 of barium oxide in the place of lime it has been possible to 1000 500 b. p. .L 99.39 807 shorten the time interval from 12 hours to 2 hours. 1000 500 b. p. 99.42 760 3 I
Experimental
PRELIMINARY DEHYDRATION-One
thousand cubic centimeters of 93 per cent (by weight) ethyl alcohol in a 2000-cc. flask were treated with 500 grams (theoretical assuming formation of barium hydroxide) of barium oxide and allowed to react on the steam cone for specified periods using a reflux condenser. The heat of reaction together with a moderate flow of steam quickly brought the reaction mixture to boiling, a t which point the steam was regulated to maintain a vigorous refluxing artion. After various periods of reaction the reflux condenser was replaced by a 60-em. condenser and the reaction mixture rapidly distilled using R small Hopkins distilling trap between the flask and the condenser. After 1 to l'/z hours' distillation the density of the distillate was determined. DENSITY DETERMINATION-A 25-cc. Ostwald pycnometer, 4 Technical grades of lump barium oxide can now be purchased in small or large amounts a t 10 cents per pound or less. A sample for this investigation was kindly supplied by the J. H. R. Products Company, of Willoughby, Ohio Acknowledgment of this courtesy is hereby made. 6 Crismer, BUZZ. soc. chim. Belg., 18, 18 (1904). 6 Noyes, J. Am. Ckem. Soc., 46, 857 (1923). 1 See reference 2 for a list of suitable dehydrating agents. 8 Winkler, Bcr., 88, 3612 (1905).
500 (99.56%) 400 (99.34%) 500 1000
50 (Ca) 10 (Ca) 500 500
b. p. b. p. 25 25
15 min. 60 min. 9 20
... ... ...
...
L
A
100.00 99.52 99.21 99.36
The data of Table I may be most profitably discussed in connection with the following reactions: BaO HoO = Ba(OH'). (la')
+
The theoretical amount of barium oxide required for the amount of alcohol dehydrated in Table I according to reaction l a is 500 grams. Reaction 16, if obtained during the early stages of the dehydration, provides for the use of less barium oxide. The reversal of reaction 16 is not appreciable at steambath temperatures. Runs 2 and 4 of Table I bring out these points. Reaction 2 takes place when barium oxide is added to absolute alcohol, resulting in the dilution of the alcohol with water, 0.4 to 0.6 per cent, depending on the temperature. The dehydration of alcohol a t room temperature (run 1, Table I) shows that barium alcoholate is not formed when alcohol of
ANALYTICAL EDITION
74
Vol. 1, No. 2
less than 99.6 per cent strength is treated with barium oxide. could be recovered. The yield of alcohol using barium oxide At the boiling point reaction 2 proceeds a t an alcohol strength is as good and generally better than that obtained using lime. of 99.4 per cent. Treatment longer than 2 hours gives no The yield of alcohol in run 9 is 92.5 per cent, if a last fraction appreciable concentration of the alcohol (runs 2 and 5). of slightly less strength after 12 hours on the steam cone is One and one-half hours' refluxing with barium oxide is too included. short a period for maximum dehydration. Three hours' General Directions treatment is not better than 2 hours' refluxing (runs 3 and 5 ) . Reactions 3 and 4 were studied by Winkler.* Reaction 3 Condensed working directions for the preparation of dry is very slow with compact metal. If the metal is finely di- alcohol are: vided and the alcohol heated, a rapid reaction takes place. ( a ) Reflux 1000 cc. of 93 per cent alcohol on a steam cone in The reaction is the less a 2000-cc. flask together with 400 grams of barium oxide for 2 rapid the more nearly hours. Replace the reflux condenser by a 30-cm. (12-inch) straight condenser and distil the alcohol l1/2 hours. Yield, a bsol u t e the alcohol. 855 I4 cc. of 99.40 per cent alcohol. More alcohol of slightly less R e a c t i o n 3 is rapid, strength is obtained by distilling for longer periods. however, on 93 to 95 per ( b ) Allow 1000 cc. of 93 per cent alcohol and 500 grams of barium oxide to react cold for 72 hours with occasional shaking cent alcohol. The calL distil as in (a). Yield, 750 cc. of 99.61 per cent alcohol. 2 10 ciuni hydroxide formed and (c) The directions in ( b ) may be duplicated with 20 hours 9 is insoluble, c a u s i n g reaction. Yield, 800 cc. of 99.36 per cent alcohol. .+.0.6 For absolute alcohol reflux any of the products obtained in alcohol to turn milky, but the calcium h y - (a), ( b ) , or (c) on the steam cone with 50 grams of metallic calcium (turnings or wire) suspended in 1 liter of the alcohol droxide does not coagu- by a6 a wire gauze basket hung through the reflux condenser. late. When the reaction of dehydration is complete, as indicated by 0.4 R e a c t i o n 4 attains the formation of a gelatinous gray precipitate of calcium ethylate, appreciable proportions the rapid evolution of hydrogen, and a noticeably exothermal reaction, remove the excess of metallic calcium and distil the 0.2 only with aIcohol above product. One hour is always sufficient for the reaction and 99.5 per cent. much less time is generally sufficient. The product thus ob5 IO 15 20 25 R e a c t i o n 5 follows tained will be found to be absolute. Time in Days rapidly after as well as Advantages of Barium Oxide as Dehydrating Agent Figure 1-Dehydration of Ethyl Alcohol s i m u ~ t a n e o u s ~ with y ..with Lime at,Room Temperature 1-The preparation of 99.4 per cent alcohol is accomplished reaction 4. The precipitate in"suspension is coagulated, gelatinous, and grayish with barium oxide using the theoretical quantity of reagent white. Hydrogen is rapidly evolved and may be tested for by refluxing less than one-fifth the time required for the prepaa t the opening of the reflux condenser in the usual manner. ration of alcohol of approximately the same strength using Too great an excess of calcium after reaction 4 has progressed calcium oxide. 2-Theoretical amounts of barium oxide reacting without materially should be avoided. Runs 6 and 7, Table I, show the rates of reactions 4 and 5, addition of heat produce 99.6 per cent alcohol in 72 hours. 3-The yields using barium oxide are in genera1 better starting with 99.56 and 99.34 per cent alcohol, respectively, The yield of alcohol given in Table I is for 1 to I'/z hours' than those obtained using lime. 4-The increased cost of barium oxide over lime is slight distillation. More alcohol could be obtained if more time were given. Counting the water absorbed, the yield of pure and the profitable recovery of the resulting barium hydroxide alcohol for@n 2 is 90 per cent. With a few additional hours' (not) discussed) as well as the saving in alcohol yield lessen heating on-the steam cone several per cent additional alcohol this apparent disadvantage.
E 2
A Self-Regulating Gas Flowmeter' Lyman Chafkfey, Jr. PENNSYLVANIA STATE COLLEGE,STATECOLLEGE,PA.
N THE:course
of some'work upon the vapor phase oxidation of benzene, it became necessary to have a means for obtaining a constant flow of air. The well-known device of a T-tube with one arm opening under water will give an approximate regulation of air pressure, but it is not very accurate. The apparatus described in this paper, although originally constructed as a makeshift to serve while more elaborate instruments were in preparation, proved so efficient that it was used for over a year and with complete satisfaction. It was designed to deliver air a t velocities up to 500 cc. pe; minute, and proved capable of continuous operation over,periods of a week or more. Description of Apparatus
I
The essential parts are an electrically operated gas valve,
a flowmeterlconsisting of a capillary tube with a manometer 1 Received
November 20, 1928.
connected across it, and means for operating the valve by the changes in the manometer level. The valve mechanism is shown in Figure 1. B is an electric bell from which the bell proper has been removed. The valve A is an ordinary automobile high-pressure tire valve. To one of the flat sides of A is soldered a bolt, which serves to fasten the valve to the bell frame. A portion of the end of valve A is cut away so that the stem, C, projects. The valve is so placed that C is hit squarely by the bell clapper, D, when this is depressed. It did not prove necessary to have this clapper vibrate and therefore the wires from the bell's magnet coils were connected directly to the binding posts. However, the end of C should be a little distance from D, so that when the coils are energized the clapper will gather a little momentum before hitting the valve stem. This whole bell-valve combination is suspended in the jar, J, by means of the lead-in wires, H.
