October 15, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
LITERATURE CITED
(1) Boutwell, p. w,, and Toepfer, E. ~ v .IN=. , ENQ, cHEM,, Anal, Ed., 4, 117 (1932). (2) Burgess-Parr Company, 111 West Monroe St., Chicago, Ill., Booklet 112. (3) Parr, S.W., and Staley, W . D., IXD.ENO. CHEM.,Anal. Ed., 3, 66 (1931).
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(4) Peterson, W. H., J. Am. Chem. Soc., 36, 1290 (1914). (5) Sherman, H. C., “Chemistry of Food and Nutrition,” 4th ed.. pp. 554-9, Macmillan, 1932. (6) Toepfer* E* and Boutwe’’, ’ w‘9 IND’ Ed., 2, 118 (1930). W’p
R E C E I V ~June D 13, 1932.
Comparative EfEciencies of Gas-Washing Bottles S. HALBERSTADT, University of Jena, Jena, Germany
D
ECISION as to the efficiency of various types of gaswashing bottles is an apparently simple matter, but one which proves quite complex on thorough investigation. Friedrichs (2), in 1919, showed that of the various devices known a t that date, only the gas washers built on the spiral-pattern principle could insure complete absorption. Since that time, apparatus with sintered-glass filter disks have been developed. I n a paper by Sieverts and Halberstadt (6) it was shown that besides the length of passage in which gas and liquid are in contact with each other, the size of the gas bubbles distributed within the liquid is also of decided importance. These results are referred to in a recent paper by Friedrichs (3). He employed mixtures of sulfur trioxide and air, both wet and dry, and tested the absorption with eleven different patterns of gas washers.
To a safety bottle and water jet air-pump
FIGURE1. MODIFIED APPARATUS
w
Gen. (apparently G1 porosity) gave about the same good results. They employed air containing 13.4 and 5.1 per cent of carbon dioxide, with velocities of flow up to 16 cc. per second-i. e., about 60 liters per hour. They mention that for the glass-filter gas washers, a comparatively higher pressure must be used. The following experiments were made in accordance with the last-mentioned paper. The gas mixture, contained in a steel cylinder, A (Figure l ) , was passed through a flowmeter (Rotamesser), then through a gas washer, E, filled with a solution of potassium hydroxide (1 to 2), and through a three-way stopcock, F , to a glass-filter gas washer, 101 G3, containing a clear solution of barium hydroxide, G. The outlet from this led to a water-jet pump. On either side of the gas washer being tested there was placed a mercury manometer D,, Dz. The differences in height between these two manometers are given in Table I as “resistance of the gas washer.” The gas washer containing the solution of barium hydroxide was constructed in the following manner: The usual groundglass stopper was replaced by a double-bore rubber stopper carrying an outlet delivery tube and a glass-filter dropping funnel, H . With the three-way stopcock, F , closed, clear filtered barium hydroxide could be drawn into the bottle from this funnel. After every experiment, the filter and the gas-washing bottle were cleaned with hydrochloric acid and carefully washed with distilled water. Then a fresh portion of 75 cc. of barium hydroxide was introduced in the same manner. The results of these experiments are shown in Table I . TABLEI. RESULTS OF EXPERIMENTS WITH DIFFERENT TYPES
Unfortunately these experiments cannot be compared with former ones because i t is well known that wet sulfur trioxide is likely to form a nebula in air and that these nebulas behave quite differently from real gases. It is difficult to absorb them in liquids, but easy to retain them by the action of filters. This is clearly shown by Friedrichs’ results. When using a moist mixture of air and sulfur trioxide, a glass-filter gas washer and a spiral gas washer filled with glass grains are most efficient, and have approximately the same effect. When using the dry mixture, the spiral gas washer filled with glass grains gives the same efficiency, owing to the considerable thickness of the filtering layer. On the other hand, the glass-filter gas washers of Schott and Gen. are less efficient because the nebulas are produced only in the thin filter disk in which the gas comes into contact with the liquid, but they are still capable of comparison with the best apparatus without glass filters. Rhodes and Rakestraw (4), who also studied these problems, came to the conclusion that the spiral gas washers of Greiner and Friedrichs and the pattern 101 of Schott and
OF APPARATU8
Av. RE-
TYPE Drechsel Greiner and Friedrichs Sohott 83 G1 Schott lOla G1
Schott 101 G3
HT.OF SISTANCE VELOCITY GIVINQREACTION LIQUID ’ OF GAS WITHBa(OH)zWITHIN5MIN. COLUMN WASHER 17% COz 3% COe 0.67% COz Mnt. Mm. H g L./hr. L./hr. L./hr. 65 05 (200 cc. KOH) length of way about 880 mm. 65 95 40 65 95 140 40 60
10
20 20
20 20
20 20
10 20
60
60 45
25
60 30 30 30 45 60 60
90
60
75
45 45 45 45 60 75 75 90
60 60 75 75 80
100 100
From these data it may be concluded that the Greiner and Friedrichs gas-washing bottle, as also found by Rhodes and Rakestraw, is useful for very many purposes. I n certain cases, however, the glass-filter gas washers proved to be superior, since with this type the lower the concentration of the gaseous component to be absorbed, the greater
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Vol. 4, No. 4
ANALYTICAL EDITION
the permissible velocity The spiral gas washer can, in all cases, be employed only up to a certain maximum velocity (60 liters per hour) independent of the gas concentration. A possible relationship might be found if the height of the liquid in the spiral washer were varied; in this case, a shorter length of the liquid column should suffice for a more dilute gas. Now with increased flow velocity, the resistances of the gas washers become of less importance. When using finer glass filters (G3), a type which was not available to Rhodes and Rakestraw, this effect becomes even more apparent. I n this connection, it is worth calling to attention a paper by Bruckner ( I ) , who made use of a gas washer, pattern lola, with a glass filter G1, for the determination of minimal concentrations of ammonia in illuminating gas. As compared with previous experiments with older types of gas washers, he could increase the flow velocity up to sixty times the previous quantity (1500 liters per hour). The filling of the spiral gas washer of Greiner and Friedrichs
with glass grains, after the example of Friedrichs, proved to be impossible in the model used, because in this case the gas passed through the filter from top to bottom, and at high velocity the glass grains were blown out of the interior chamber.
ACKNOWLEDGMENT The author wishes to thank the Janaer Glaswerk Schott and Gen. for kindly placing a t his disposal the necessary apparatus and the steel cylinders containing the gas mixtures that were used.
LITERATURE CITED Bruckner, H., Gas- u. Wasserjach, 74, 121 (1931). Friedrichs, F., 2. angew. Chem., 32, 252 (1919). Friedrichs, F., Chem. Fabrik, 4, 203 (1931). Rhodes and Rakestraw, IND.ENQ. CHEM.,Anal. Ed., 3, 143 (1931). ( 5 ) Sieverts, A., and Halberstadt, S., Chem. Fabrik, 3, 201 (1930).
(1) (2) (3) (4)
RBCEIVED May 9, 1932.
Rapid Determination of Small Amounts of Magnesium in Presence of Phosphates W. E. THRUN, Valparaiso University, Valparaiso, Ind.
T
H E most commonly used micromethod for determining magnesium in biological fluids or ash consists in precipitating the magnesium as magnesium ammonium phosphate from the filtrate of a calcium determination and determining the phosphorus colorimetrically (2,6). BeEka ( 1 ) described a method based upon the formation of a lake by magnesium with Titan yellow. The method presented here does not require the time needed to perform a determination by the first method nor as many preparations as the second. It is suitable especially for laboratories in which such magnesium determinations are not a routine matter. The determination is based upon the formation of a lake by magnesium with curcurmin (3) in the presence of sodium hydroxide, and its colorimetric comparison with standards prepared simultaneously. The phosphates affect the color of the lake suspension but, if the standard solution also contains dissolved tricalcium phosphate, the color intensities are comparable and in proportion to the amount of magnesium present. Variations in the relatively large amounts of calcium phosphate added in no way affect the color intensities of the standard solution. This fact'and a difference in color shade suggests the formation of a magnesium-curcurminphosphate lake. The lake suspensions may be made more stable by the addition of starch glycerite solution (4). The removal of iron if present in too large quantities is also provided for. PROCEDURE. Pipet an aliquot of the ash solution (containing about 2 cc. of concentrated nitric or hydrochloric acid per liter) which is equivalent to 0.02 to 0.04 mg. of magnesium into a 50-cc. Nessler tube or volumetric flask. Dilute to about 40 cc., and add 2 cc. of starch glycerite solution (prepared by shaking some of the jelly with water and filtering) and 4 drops of a 1 per cent alcoholic solution of curcurmin. Since it is important that the unknown and standard solutions receive the same amount of curcurmin, this should be added with a pipet made for the purpose from a capillary tube. Mix contents thoroughly and add 5 cc. of 4 N sodium hydroxide. Mix again, dilute to mark, and mix.
One or several standard solutions are treated simultaneously in the same way. A standard solution containing 0.02 mg. of magnesium per cc. is prepared by dissolving 0.203 gram of MgS04.7HzO and 0.1 to 0.4 gram of tricalcium phosphate in water containing 2 cc. of concentrated nitric acid and diluting to one liter. In Nessler tubes distinct color intensities are distinguishable with differences of 0.01 mg. of magnesium. The color intensity is, however, less than is desirable for an instrument which allows for a depth of only 5 cm. The Nessler tubes may be used as colorimeters by varying the depth of liquid in them. The solutions are diluted so highly in order to prevent the rapid formation of a tricalcium phosphate precipitate. The lake suspensions are stable for several hours. When viewed through the Nessler tubes the suspensions appear to be slightly cloudy. If iron is present in sufficient quantity so that an appreciable colored suspension is formed upon adding the sodium hydroxide and diluting, it may be removed as follows: Titrate a separate aliquot with dilute sodium hydroxide to the neutral point of methyl red (pH 4 to 5 ) . Add the same amount of sodium hydroxide to the aliquot to be used and filter or centrifuge out the precipitate. At that pH, the magnesium phosphate is still soluble. When borates are present in excess of 0.6 mg. (as the oxide) magnesium-free blanks are affected slightly. The color intensities of blanks varying in boric oxide concentration from 1.4 to 8 mg. were the same. Two lake solutions were made up according to the directions given above containing 0.03 mg. of magnesium and 0.6 mg. of tricalcium phosphate. One of them contained in addition 6 mg. of boric oxide. The color intensities of both solutions were apparently the same. The slight effect, if any, of borates when present in larger amounts than 0.6 mg. can be eliminated in two ways. A solution containing 2 mg. of boric oxide may be added to each of the standard aliquots, or the sample aliquot may be evaporated to dryness with hydrochloric acid and methyl alcohol to remove the boric acid and the residue taken up with a
