T H E J O C R N A L OF I,VDUSTRIAL A N D ENGINEERING C H E M I S T R Y A METHOD FOR THE DETERMINATION OF CARBON DIOXIDE IN BAKING POWDER AND CARBONATES B y H. W. BRUBAEER Received December 7 , 1914
The lollowing is t h e result of a n a t t e m p t t o devise a method for t h e determination of t h e available carbon dioxide in baking powders, which is simple in principle, requires a n apparatus easy t o construct, a n d manipulate, consumes little time a n d gives reasonably accurate results. T h e method was devised for t h e use of a class of girls in household chemistry. It is adapted not only t o t h e determination of carbon dioxide in baking powder b u t also in carbonates, bicarbonates a n d minerals such as limestone and dolomite. The principle of t h e method, in brief, is t h e liberation of t h e carbon dioxide, causing it' t o displace its own volume of a saturated solution of sodium chloride into a graduated cylinder a n d measurement of t h e volume of t h e solution displaced. A s a t u r a t e d solution of salt is used because carbon dioxide is n o t readily dissolved in i t a n d tests show t h a t under t h e condi-
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funnel b y opening t h e stopcock, care being taken n o t t o admit a n y air. The carbon dioxide begins t o be liberated a t once a n d t h e salt solution is driven over into t h e graduated cylinder E . The decomposition of t h e baking powder is completed b y heating with t h e gas burner until t h e solution has boiled for two or three minutes or until t h e rise of t h e salt solution in t h e cylinder E is seen t o have stopped. The flame is t h e n turned out a n d t h e a p p a r a t u s allowed t o s t a n d until i t has cooled t o room temperature again. The cooling of t h e flask A can be hastened, if desired, by lowering t h e ring a n d bringing a beaker of cold water up under t h e flask until i t is immersed i n t h e water. When t h e a p p a r a t u s has reached room temperature t h e salt solution in E a n d B is leveled u p b y raising E . T h e pinch clamp is t h e n closed; t h e cylinder E is lowered t o t h e table, t h e delivery tube removed a n d t h e volume of salt solution in E read. S u b t r a c t 2 5 cc. from this volume t o compensate for t h e z j cc. of salt solution which were run into t h e flask A t o decompose t h e baking powder. Correct t h e remaining volume t o o o C. a n d 760 mm. pressure. As 5 . I cc. of carbon dioxide gas a t o o C. a n d 760 m m . pressure weigh 0.01 g., which is one per cent of 1 . 0g., t h e per cent of carbon dioxide i n t h e baking powder m a y be found b y dividing t h e corrected volume b y 5 . I . K O T E : I n making t h e correction for aqueous tension I have used t h a t for pure water which is t w o or three m m . too high in each case. The effect of t h e small error t h u s introduced into t h e results here recorded is t o make tliem too low. RESULTS
The purpose of t h e condenser i n t h e a p p a r a t u s is t o prevent a n y water from distilling over i n t o t h e c y l i n d e r 3 a n d t h u s diluting t h e salt solution. Table I shows some results obtained with various baking powders: TABLEI-ANALYSES
BAKINGPOWDERSFOR COa BaromSample Vol. COz Temp. eter Per cent Baking powder Cc. C. Mm. COS 20 740 11.30 Royal A 1 65.0 20 740 11.47 2 .............................. 66.0 21 742 11.43 Royal B 1 66.4 13.47 78.3 22 740 Calumet A 1 23 740 13.34 2 . ............................ 77.9 13.69 82.0 29 745 Calumet B l . . . 24 745 11.14 65.0 25 745 11.02 64.5 OF
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tions of t h e experiment t h e amount of absorption is so small t h a t i t m a y be neglected. A saturated solution of salt is also used, instead of water, in t h e decomposition of t h e baking powder. The principle of collecting carbon dioxide over a saturated solution of sodium chloride is used b y Jago in determining t h e strength of yeast. PROCEDURE
One gram of t h e baking powder is placed in t h e flask A . Water is circulated through t h e condenser for several minutes. T h e cylinder B is nearly full a n d t h e delivery t u b e C is full, t o t h e open end, of a s a t u r a t e d solution of salt, t h e pinch clamp being closed. The stopcock in t h e funnel D is now closed a n d exactly 2 5 cc. of a saturated solution of salt placed in t h e funnel. The pinch clamp on t h e delivery t u b e is now opened a n d t h e salt solution r u n in from t h e
I n order t o ascertain whether a n appreciable a m o u n t of carbon dioxide is absorbed b y t h e salt solution during a determination, 90 cc. of carbon dioxide were r u n into t h e a p p a r a t u s at 2 2 ' C. a n d 740 mm. a n d allowed t o s t a n d 2 hours a n d 40 minutes, a t t h e e n d o f which time t h e volume was 9 0 . 3 cc. a n d t h e temperat u r e 2 3 ' C., t h e pressure having remained t h e same. T h e increase in volume is very close t o t h a t which would result from t h e increased temperature. I n applying t h i s method t o t h e determination of carbon dioxide in carbonates such as sodium carbona t e a n d precipitated calcium carbonate t h e sample was decomposed b y means of a dilute solution of hydrochloric acid which was saturated with sodium chloride. T h e absorption of carbon dioxide b y t h e acid solution is appreciable and must be allowed for.
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T H E J O U R N A L O F I N D U S T R I A L A N D E N G I N E E RI NG C H E M I S T R Y
This is done b y decomposing one sample with I O cc. of t h e acid solution, t h e n running a second determinat i o n , using 1 5 cc. of acid. T h e difference in t h e a m o u n t s of carbon dioxide obtained in t h e t w o cases being d u e t o t h e absorption b y j cc. of acid solution, t h e proper correction is made on either determination. When decomposing p re ci p it a t e d c arb ona t e s with h ydrochloric acid no heating is necessary, hence t h e t i m e consumed in each determination is very s h o r t , b u t t w o or t h r e e minutes being required for t h e liberation of t h e carbon dioxide. I n running t w o samples of calcium carbonate in t h i s way, t h e whole process, including t h e weighing of t h e samples, required only t e n minutes. Table I1 shows some of t h e results obtained o n carbonates. I n Determinations I a n d z h e a t was used. I n Determination 3 no heat was used. T h e sample of sodium carbonate used in determinations 4 a n d 5 was found t o contain 4.46 per cent of moisture. T h e theoretical am-ount of carbon dioxide in this sample TABLE11-ANALYSIS Decom LVt. posed Detn. taken by cc. No. Sample Gr. acid 5 1 CaCOs 1/4 10 1/4 3 2 CaCOa 1/4 8 ;/4 8 3 CaC03 12 13 1/2 7 4 SazCOs ‘/a 12 1‘2 7 5 SazCOa 1/2 ’/a 12 6 D r y Na2COa ‘/a 7 7 Limestone 1/a 10 15 ‘/2 ( a ) By difference; see text.
OF
CARBONA?:ES FOR
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Vol. CO2 T e m p . Bar. PERCEXT COz c. m m . Found Theoretical cc. 62.5 23 143.98 44.00 6 1 . 0 25 6 4 . 0 24 5:;)43.88 44.00 6 3 . 5 25 1 2 7 . 0 25 53355)43.98 44.00 124.65 25 1 1 6 . 0 25 ;::/39.95 39.65 113.88 25 1 1 6 . 0 25 39.95 39.65 113.88 25 118.2 24 742 41.38 41.50 111.5 25 38.18 38,45(a) 113.5 2 8 . 3
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is therefore 39.6j per cent. Some of t h i s sodium carbonate was now dried a n d Determination 6 made upon t h e d r y sample with t h e result shown. Allowing for t h e same absorption a s in Determination s, which is 2 . 9j cc.. gives a t o t a l volume of I z I . I 7 cc. under t h e above conditions of t e m p e r a t u r e a n d pressure v h i c h correspond t o 41.38 per cent of carbon dioxide.
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Determination 7 was made on a sample of limestone. It n-as necessary t o use heat t o completely decompose t h e sample with t h e acid solution. I had no gravimetric determination of carbon dioxide in this limestone against which t o check t h e result. However, according t o t h e figures of another analyst, t h e limestone contains 1 2 . 28 per cent S O 2 , I . I j per F e 2 0 3 , 46.74 per cent CaO a n d 1.38 cent per cent I I g O , making a t o t a l of 6 1 .j s per cent, which leaves for carbon dioxide 38.4j per cent. This makes no allowance for potassium a n d sodium which m a y be present in very small quantities. T h e result is undoubtedly a close approximation t o t h e actual percentage of COz present. K O T E ( J a n . 1 1 , 191j): Since sending this paper for publication I have found a convenient way of obviating t h e necessity of making a correction for t h e absorption of carbon dioxide in those cases where t h e sample is decomposed b y dilute acids. T h i s makes i t unnecessary therefore, t o decompose more t h a n one sample of t h e substance for one determination. T h e procedure is a s follows: J u s t before making t h e determination pour 30 or 40 cc. of dilute hydrochloric acid (I acid : 3 water) on 0.5 g. of precipitated calcium carbonate. W h e n t h e effervescence h a s ceased, a n d t h e acid solution h a s become clear, pipette I O cc. of t h i s i n t o t h e bulb of t h e separatory funnel a n d proceed with t h e determination. This method of saturating t h e acid with carbon dioxide requires b u t a moment a n d makes it unnecessary t o correct for a n y absorption whether t h e sample is decomposed b y heating or a t room temperature. T h e following determination will illustrate t h e accuracy of t h i s method of procedure :
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Wt. of limestone taken. ........................... 0.5 g. Volume of salt solution displaced.. . . . . . . . . . . . . . . . . . 138.18 cc. 739 mm. Temperature. 22’ C. Barometer.. . . . . Volume corrected t o 0’ C. a n d 760 mm... . . . . . . . . . . . 112.3 cc. 44.03 Per cent Con f o u n d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Theoretical per cent CO2 .,.,. 44.00 DEPARTMENT O F CHEMISTRY KAXSASSTATE AGRICULTURAL COLLEGE MANHATTAN
ADDRESSES THE FIXATION O F , A T M O S P H E R I C NITROGEN‘ By IT. S. LASDIS
I t is nom some three years since I h a r e occupied this side of the lecture table, and I can assure you this is a most delightful occasion’to me, not only because I can here omit the tedious routine of taking a n attendance record of my class, but also because it is my first opportunity to tell t h e chemical and engineering professions something about the interesting work I have been engaged in since giving up university teaching. I am going to assume that you are all more or less familiar with the use of nitrogen in one or more of its various combinations, for t o catalogue even a partial list of the most common commercial nitrogen compounds would read like a few pages out of 31r. Olsen’s “Chemical Annual,” or from the “Chemiker Kalender.” I a m not even going to bore you with statistics of consumption of the nitrogen comppunds, because t h e very complex nature of these statistics would make them difficult of comprehension if merely read from prepared tables, and I bel Presented before t h e Washington Section of t h e A . C. S. on March 17, 1915, and before t h e Philadelphia Section of the A . C. S , March 18, 1915.
liere our time can be better occupied along other more interesting lines intimately connected with our subject. I shall add only that in tonnage alone the nitrogen compounds stand well at the head of the list of the world’s trade in heavy chemicals, nitrate of soda and sulfate of ammonia bring produced in 1913 t o the value of S~oo,ooo,ooo. S o t including atmospheric nitrogen, whose utilization is yet in its infancy, we are practically dependent for our suppi?; of this valuable element upon the nitrate deposits of Chile, and its recovery as a by-product from our luels. The Chilean deposits
have been so frequently and fully described elsewhere that we can omit reference to the same here. The end of this source of supply is, however, in sight, and it will be only a few years until Chilean nitrate will pass into history along with our anthracite coal and the Saxon silver-lead ores. The recovery of ammonia as a by-product from fuel is entirely different, since for many centuries t o come, we shall have an ever-increasing source of this element in the coke oven and the gas producer, from which i t is obtained in one of its most valuable forms of combination, ammonia. This source
