Apr.9 1914
T H E J O U R N A L 5 F I N D U S T R I A L A N D E N G I N E E R I N G CH E M I S T R Y
alkaline by sodium hydroxide a deep red color is produced. Of nine men in t h i s laboratory, however, who took prescribed doses of senna-in preparations compounded with syrup of figs-in only two cases were positive tests given on examination of t h e urine twelve hours later.' The applicability of chrysophanic acid for purposes of artificial coloring are apparent, one instance having been cited recently by Thum.* The sophistication of powdered rhubarb with powdered turmeric has been practiced and Howie3 and others have given some a t tention to the detection of curcumin in such cases. I n t h e inspection of patented and other medicinal preparations, the detection of chrysophanic acid serves t o indicate t h e presence of a restricted group of vegetable constituents. And, finally, t h e similarity of many of its reactions t o those of phenolphthalein, a substance of not uncommon okcurrence in medicines, makes its detection in presence of t h a t substance desirable. If a n alcoholic extract containing chrysophanic acid is dealcoholized or sufficiently diluted with water, acidified with a few drops of concentrated hydrochloric acid and shaken out with ether,4 the coloring matter is taken up b y t h e solvent and t h e ethereal layer is colored yellow. On washing the solvent with dilute alkali ( ~ 1 , ' ~per cent ammonium hydroxide was used) t h e color is transferred t o the aqueous solution which is colored red. Similarly treated, picric acid and t h e color principle of hydrastis yield no red color t o dilute alkali nor does their presence interfere with subsequent tests; but curcumin, haematoxylin, and phenolphthalein yield colors not to be distinguished in certain concentrations from t h a t produced by chrysophanic acid. I n the cases of curcumin and haematoxylin, however, the color of their alkaline solutions is slowly fugitive. After standing over night a t 40°1500 the red element is entirely lost, b u t the red color of chrysophanic acid and phenolphthalein is persistent.
I
If this solution is now acidified and shaken out with ether, the interfering color principles, curcumin and haematoxylin, are eliminated. Their absence can be demonstrated by concentrating a portion of the ether shake-out on filter strips and testing as follows: ( I ) Moisten one of the strips with a drop of strong hydrochloric acid. K O pink color will be obtained, showing the absence of haematoxylin. (2) Moisten another strip with a mixture of hydrochloric-boric acids. N o red color will be produced, showing the absence of curcumin. (3) Moisten a third strip with dilute ammonium hydroxide. A pinkish red color will indicate t h e presence of chrysophanic acid or phenolphthalein or both. To eliminate phenolphthalein transfer a portion of the ether shake-out obtained above t o a test tube and drive off the ether. Add a little zinc dust and 4-5 cc. of 2 5 per cent sodium hydroxide, boil until the red color is discharged and cool the solution. By this treatment chrysophanic acid is reduced, as already described, the solution becoming yellowish, and phenolphthalein is reduced t o phthalin which is colorless. Dilute the alkaline solution with water or treat it with a few drops of hydrogen dioxide and t h e characteristic cherry-red color of chrysophanic acid will be obtained. Phthalin remains unoxidized under these conditions. Curcumin and haematoxylin both undergo reduction by means of zinc dust and sodium hydroxide and neither are subsequently oxidized by hydrogen dioxide, but their yellow or brown solutions mask the color of chrysophanic acid in certain proportions and thus ,make t h e test for t h e latter less distinct. I t is therefore best t o eliminate these substances by the method described. ANALYTICAL LABORATORY AGRICULTURAL EXPERIMEN STATION T CONNECTICUT N E W HAVEN
LABORATORY AND PLANT
IMPROVEMENTS IN THE IODINE PENTOXIDE METHOD FOR!THEiDETERMINATION OF CARBON MONOXIDE IN AIR By ATHBRTON SBIDBLL Received January 10, 1914
The iodine pentoxide method is based upon t h e reaction 120s g C 0 = ;COS Iz which has been found to be quantitative a t approximately I 5 0 ' . The sample of air is passed first through absorption tubes containing potassium hydroxide and concentrated sulfuric acid and then through a U-tube containing powdered iodine pentoxide, and immersed in an oil bath heated t o 150'. It is obvious t h a t either the resulting iodine or the carbon dioxide may be used as the measure of the carbon monoxide.
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1 These tests were made with commercial laxative preparations in which senna was declared to be an ingredient. The amounts of senna in many cases may have been too small to give the physiological test. 2 A m . J . Pharm.. 85, 1 , 19. 8 Pharm. Jour., Nov., 1873; also Am. J. Pharm.. 4 (1874): 1, 16. 4 The emulsion which forms is readily destroyed by adding acetone.
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The apparatus as usually described' consists of a series of U tubes, spiral or other absorption tubes and potash bulbs connected with a suitable aspirator. On assembling a n apparatus according to the usual descriptions, i t became evident t h a t a reduction of the dead air space would materially shorten the time required for a determination and reduce the correction factor resulting from t h e slight decomposition of t h e iodine pentoxide reagent by the air used t o drive the sample through the apparatus.: I t was also hoped t h a t t h e rate a t which the sample is drawn through the apparatus could be increased. The improved apparatus which has been developed is shown in t h e accompanying diagram. The essential feature of i t is the special form of absorption 1
Nicloux, Compt. rend., 126 (1898), 746; Kinnicutt and Sanford,
J. Am. Chem. Soc., 22 (1900), 14; Levy and Pecoul, Compl. rend., 140 (1905), 98; 142 (1906), 162; Morgan and McWhorter, J. A m . Chem. Soc., 29 (1907), 1589; Weiskopf, J . Ckem. M e t . SOL.S. Africa, 9 (1909): 258, 306; and also Chem. News, 100 (1900). 191; Goutal, Ann. chim. a n d 16 (1910), 1-7; Levy, J . SOL.Ckem. I n d . , S O (1911), 1437.
aPPl.,
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
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bulb which has been adopted. A brief note on this bulb has been recently published.' As will be seen, the apparatus has been so arranged t h a t t h e air sample is automatically transferred by water displacement from its container S t o the reservoir R by way of the train of absorption bulbs and U tubes B, H, K , L, P and Q. The fixed level N of the end of t h e return tube M insures a constant hydrostatic pressure during the flow of t h e water from t h e upper to the lower bottle. The rate of flow is regulated by the screw pinch-cock C and the air pressure in the system, as indicated by the manometer I, is controlled by means of t h e cock U. The two sets of bulbs a t A contain, respectively, concentrated sulfuric acid and aqueous KOH solution ( I : I ) for purifying t h e laboratory air used for washing the sample through the apparatus. Bulbs H con-
tain concentrated sulfuric acid. The upper of the double bulb a t the right was filled with glass wool to prevent possible splashing of t h e acid into t h e U tube K which followed, and contained small lumps of potassium hydroxide. This U tube K and the following one L containing the iodine pentoxide were each made of a continuous glass tube and the two sealed together. The U tube L was immersed in the oil bath 0. The iodine pentoxide was rather finely powdered and introduced in layers alternating with glass wool. Pure air was drawn through t h e tube heated t o 1 5 0 ~ - 2 0 0 for ~ several hours previous to beginning determinations upon air samples containing carbon monoxide. 1
Seidell. J . Am. Chcm
306,
811 (1913), 1888.
Vol. 6 , No. 4
The procedure for a determination is as follows: the reservoir R is filled by opening cock F,[closing cock J and turning on the water a t W. The stopper of the 2 5 0 0 cc. sample bottle is replaced by the stopper V with its two glass tubes. These are then connected as shown a t D and E. The carbon dioxide absorption bulbs B are then filled with I O cc. of the stronger standard barium hydroxide solution (approximately O . O j normal) and the bulbs Q with I O cc. of the diluted standard barium hydroxide solution (approximately 0.005 normal). The bulbs P for retaining the iodine are filled with 5 cc. of I per cent aqueous pbtassium iodide solution plus 0.5 cc. of 0.5 per cent arrowroot starch solution. When all connections are made cock F is closed, the cocks J and U are opened and the screw pinch-cock C so adjusted t h a t the water flows through a t the rate of about two to three liters an hour. Although this is about six times as fast as Kinnicutt and Sanford specify, and three times as fast as Goutal prescribes for the apparatus described b y him, there was no evidence of incomplete absorption of iodine a t any time and only a slight loss of carbon dioxide in case of samples containing enough of this gas to nearly saturate the barium hydroxide solution. T h e three volumetric solutions used for titrating the contents of the three absorption bulbs B, P and Q were, respectively, oxalic acid containing j.632j grams per liter (each cubic centimeter therefore corresponding t o one cubic centimeter of COz a t o o and 760 mm.), one-thousandth normal thiosulfate and oxalic acid solution of one-tenth the concentration of t h e stronger standard. The standardization of the thiosulfate is made under conditions as nearly identical as possible with those under which the titration of the contents of bulbs P are made. Standard 0.001 .normal iodine is prepared b y dilution of a 0.1 normal solution and to quantities of this within the range of the amounts to be determined, is added enough potassium iodide t o yield approximately I per cent of the latter and the titrations made t o disappearance of the blue starch color with 0.001 normal thiosulfate. The choice of the I per cent concentration of potassium iodide was made on t h e basis of experiments with the absorption of iodine in bulbs P. Stronger solutions than I per cent caused the starch, which was added to assist in t h e retention of theliodine and as an indicator,' t o flocculate in the form of blue granules. With larger quantities of iodine than encountered in the analysis of the samples of tunnel air i t would probably be necessary t o select other proportions of the several reagents t h a n here specified for the particular conditions in hand. I n order t o ascertain the degree of accuracy t o Le expected by the iodine pentoxide method a series of determinations was made with known amounts of carbon monoxide diluted with laboratory air. The carbon monoxide for this purpose was prepared by mixing concentrated sulfuric acid and sodium formate I The absence of the blue color in the third of the series of three bulbs used for the potassium iodide-starch paste reagent shows that the iodine has been completely retained in the first and second bulbs.
Apr., 1914
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
in a t e s t tube and after displacement of t h e air in t h e tube, collecting the evolved gas over water. Successive dilutions of this were made and I O to I O O cc. portions of t h e final mixture, corresponding to t h e volumes of carbon monoxide shown in Column 2 of the accompanying table, were introduced into partially evacuated 2 j o o cc. bottles a n d these samples, which contained from 36 t o 3 6 0 parts of carbon monoxide per million, were drawn through the absorption apparatus as described above. DETERMINATIONS U P O N M I X T U R EOF S KNOWN AMOUNTS OF PURE CARBON A N D LABORATORY AIR MONOXIDE COz BULBS Q IODINEB U L B S P I O cc. approx. CO? B U L B S B 5-10 cc. aq. 1% 0.005 N Ba(OH)? I O cc. approx. 0.1% starch used for each det. KI 0 05 N Ba(OH)r used for each det. used for each det. I3 , _ _ * , (COOH)z (at 0' and 0.001 A' Calc. CO for Calc. CO (COOH), for Calc. 760 mm.) parts thio. for (at O o and excess (at 0' and excess of per 2.500 Ba(OH)Z CO? per evolved I 760 m m . ) B a ( 0 H ) s 760 mm.) cc. of air. cc. cc. cc. cc. cc. 10,000 cc. 14.8 0.79 .. ... .. .. 0.90 7.65 0,405 2.15 0.345 2.6 13.0 0.456 7.3 0.386 2.55 0.30 4.35 6.0 0.456(ai .. .. 7.5 0.40 .. ... 0 45 4.0 0.207 2.8 0.28 3.3 10.2 0,229 4.5 0.18 3.8 0.196 3.8 5.4 0.229(a) 4.1 0.212 3.35 0,225 4.0.5 7.2 0.228 . ... 4.1 0.212 0 . 22s 3.95 0.20 .. ... n , 225 1.85 0.09 4.3 0.13 4 2 6.6 n , 092 1.75 0.084 .. ... .. 0.09 .. .. 1.75 0.084 .. ... 0.09 4 2 6.6 0.2 ... 4.9 ... n.nn
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( a ) The mixture of CO air stood over water two days before analysis. Factor for 0.001 N thiosulfate = readings X 0.97 = 0.001 A' exactly. 1 cc. 0.001 X thiosulfate = 0.056 cc. CO (at 0' and 760 mm.). 10 cc. approx. 0.05 N B a ( 0 H ) z = 5.85 cc. (COOH),; 1 cc. (COOH)g = 1 cc. COI (at 0 ' and 760 mm.). 10 cc. approx. 0.005 N B a ( 0 H ) s = 5.6 cc. (COOH)?; I cc. (COOH)? = 0.1 cc. CO? (at 0" and 760 m m . ) .
Blank determinations made by drawing 2 5 0 0 cc. portions of laboratory air through t h e iodine pentoxide tube heated to x j o 0 , gave blue colorations in bulbs P which required 0.2 cc. and sometimes as high as 0.4 c c . of 0.001LV thiosulfate for their discharge. These amounts, no 'doubt, correspond t o the carbon monoxide normally present in t h e laboratory air and do not indicate a faint spontaneous decomposition of the iodine pentoxide. The correction of 0.2 cc. has therefore been applied to the thiosulfate titrations given in the table, since in these cases t h e estimation of the added carbon monoxide only was desired. I t will be observed t h a t in t h e present experiments slightly low results for carbon monoxide were obtained in all cases. The amounts recovered varied from 88 t o 98 per cent, t h e lower percentages being obtained with t h e higher amounts of carbon monoxide. 'Although on the percentage basis this appears t o be a considerable loss, as a matter of fact when the very minute amounts of gas are taken into consideration t h e differences are quite small. In regard to the carbon monoxide determinations based upon t h e titrations of the contents of bulbs Q it is seen t h a t unaccountable irregularities are obtained. Tn most cases t h e amounts of carbon monoxide recovered were considerably lower t h a n found by the iodine titration. I t may, therefore, be concluded t h a t
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for t h e concentrations of carbon monoxide under consideration, no increased confidence in the results is t o be obtained by using t h e carbon dioxide titration as a check upon the iodine titration. HYGIENIC LABORATORY, WASHINGTON, D. C
CONVERSION CURVE FOR LOVIBOND'S TINTOMETER AND STAMMER'S COLORIMETER B y CARLA. NOWAK Received January 20. 1914
I n compliance with a request recently received asking me t o construct a table correlating the readings taken on the Lovibond tintometer, inch cell, series j 2 , and those obtainable with the Stammer colorimeter, I have carried out a number of comparative color determinations with these two instruments using a n 8 % malt wort, and plotted t h e results in a form of a conversion curve. I n order to verify the readings and to determine the extent of experimental error due to personal factors, such as variation in color vision, all readings 60
ss
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35
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were taken b y two persons, with the unexpected result, t h a t in no case did the readings vary by more than 2 degrees Stammer or more t h a n 0.2 to 0.3 degree Lovibond. All readings were taken a t the same temperature, a h . , I j Centigrade. After plotting t h e tabulated results i t was found t h a t an almost ideal curve was obtained, showing t h a t with a careful manipulation very slight differences in color can be detected with either of these instruments. For the benefit of any who may not have access to both instruments and wish to convert the readings of
