June, 1915
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
Table I1 should be compared with t h e analyses reported b y m i n t o n and Berry.‘ The influence of sugar or glycerine in t h e menstruum on the amount of acidity a n d ash extracted was hardly appreciable. Decreasing t h e strength of t h e alcohol increased t h e amount of ash and diminished t h e acidity. S U M S IA R Y
I-The following ranges in acidity a n d in ash values were found in 7 7 U . S. P. extracts made i n t h e laboratory from different varieties, grades and lengths of vanilla beans: TOTAL ACIDITY:
30 to 52 cc. N/10 alkali per 100 cc. ACIDITYOTHER THAN VANILLIN: 14 t o 42 cc. “10 alkali per 100 cc. TOTAL ASH: 0.220 to 0.432 gram per 100 cc. SOLUBLE ASH: 0.179 t o 0.357 gram per 100 cc. OF TOTAL ASH: 30 to 54 CC; N/10 acid per 100 CC. ALKALINITY ALKALINITY OF SOLUBLE ASH: 22 to 40 cc. hr/10 acid per 100 cc.
11-Practically t h e same values were obtained with a n d without t h e use of sugar or glycerine in t h e menstruum. 111-Diminishing t h e strength of alcohol in t h e menstruum tended t o increase t h e ash values and diminish t h e acidity. IV-The possibility of developing a method of determining vanillin based on t h e acidity is suggested. BUREAU OF CHEMISTRY, WASHIBGTON, D. C.
A MODIFICATION O F WICHMANN’S M E T H O D F O R THE DETECTION OF SMALL AMOUNTS O F COUMARIN, PARTICULARLY I N FACTITIOUS VANELA* EXTRACTS By J. R. DEAN Received April 9, 1915
..
The essential part of t h e Wichmann method for the detection of coumarin in vanilla extracts is t h e conversion of t h e coumarin, in t h e residue obtained b y evaporating t h e distillate from a vanilla extract t o dryness, into salicylic acid b y fusion with potassium hydroxide a n d testing for salicylic acid with ferric chloride. Saccharin and salicylic acid interfere completely with this test. The following modification of TVichmann’s method has been found t o be as useful as the original, is much less troublesome a n d is not interfered with by either salicylic acid or saccharin. Render a de-alcoholized portion of t h e extract alkaline with j cc. of ammonia (use of the residue after a n alcohol determination is recommended) and extract with I 5 cc. of ether.3 Iranillin, salicylic acid and saccharin are insoluble in ether in t h e presence of ammonia while coumarin is readily dissolved. Transfer t h e ether t o a nickel or porcelain crucible and evaporate on t h e steam b“ath or hot plate. Add five drops of a j o per cent solution of potassium hydroxide and, after carefully drying, fuse a t t h e lowest possible temperature, care being taken t o avoid any blackening. Dissolve t h e mass i n a few cc. of water, render acid with dilute sulfuric acid a n d transfer t o a test tube. Add j cc. of Lac. C i l . Method for the Detection of Small Amounts of Coumarin. Particularly in Factitious Vanilla Extracts,” by H. J. Wichmann. Circular 96, U. S. Dept. of Agr., Bureau of Chemistry. Hess and Prescott, J. A . C. S., 28 (1899), 256. 1
’ “A
519
chloroform t o dissolve out t h e salicylic acid produced i n t h e fusion a n d shake t h e t u b e vigorously. Xllow t h e chloroform t o separate a n d remove i t with a small pipette extended t o t h e bottom of t h e tube. Transfer t h e chloroform t o a second test tube, filtering through a small plug of cotton. Add I or z cc. of water, containing a drop or two of ferric chloride solution, t o the chloroform and shake a s before. The presence of coumarin is indicated b y t h e formation of t h e purple color of ferric salicylate. TABLEOF R ~ S U L T S SAMPLES Extract of vanilla plus A’othing 25 mg. salicylic acid 25 mg. saccharin 1 mg. coumarin 2 . 5 mg. coumarin 5 mg. coumarin 5 mg. coumarin 25 mg. salicylic acid 25 mg. saccharin 25 mg. coumarin
No. of samples Results 4 Negative 4 Negative 4 h’egative 4 Positive 4 Positive 4 Positive
1\
Depth of purple color
Light purple Strong purple Deep purple
4
Positive
Deep purple
4
Positive
Very deep purple
I t does not seem possible t o employ t h e above reaction i n a n accurate quantitative method for coumarin t h a t would be a n y shorter or better t h a n t h e extraction method now employed. By experience, however, one can learn t o form a very good idea of t h e amount of coumarin present b y t h e depth of color obtained. Attention is called t o t h e f a c t t h a t coumarin would interfere with Durand’sl test for saccharin as both coumarin a n d saccharin yield salicylic acid when fused with either potassium or sodium hydroxide. It is possible t o eliminate t h e saccharin, as stated above, b u t as coumarin is of such a n inert nature chemically, i t s removal is far less easy-an extraction b y means of a n immiscible solvent in t h e presence of an alkali being t h e method generally used. Coumarin a n d saccharin are very likely t o be found together in food products, especially in soft drinks of a cheap nature where coumarin has been used in place of, or with, vanilla or vanillin. I n using Durand’s test for saccharin i t would be necessary t o remove the coumarin b y rendering t h e substance alkaline a n d extracting as above. After t h e complete removal of t h e coumarin, t h e sample under e x a m h a t i o n could be rendered acid a n d tested for saccharin as in Durand’s method. 520 CHURCH STREET,ANH ARBOR,MICHIGAN
STUDIES I N SYNTHETIC DRUG ANALYSIS 111-ESTIMATION O F CAFFEINE AND ANTIPYRIN I N
ADWXTURE By
a‘.0. EMERYA N D
S. PALKIN Received March 20, 1915
The first recorded attempts looking t o t h e quantitative separation of these two drugs were apparently made by J . J . Hofman,2 who, taking advantage of the tendency of antipyrin t o yield with mercury salts difficultly soluble products, subjected t h e caffeineantipyrin mixture t o t h e action of mercuric nitrate, thereby precipitating t h e antipyrin as t h e molecular compound CllHl2N20.Hg(N03)2. After separating t h e precipitate b y filtration, t h e caffeine was isolated from a n aliquot of t h e filtrate by extraction with chloroform a n d estimated as pure caffeine. The weight of the 1
Halsey Durand, THISJOURNAL, 6 (1913), 987.
2
Pharm. Weekblad, No. 49 (1894).
,
I
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 original mixture having been previously ascertained, t h a t of antipyrin could of course be readily calculated. As already pointed out b y Zernik,’ t h e method is faulty i n t h a t t h e precipitation of antipyrin with mercuric nitrate is not quantitative, a portion of t h e molecular compound remaining dissolved in t h e liquid as shown b y t h e isonitroso reaction. T h e result is t h a t caffeine separated in this manner is never quite pure b u t is contaminated with a n appreciable quantity of antipyrin in t h e f o r m of its combination with mercuric nitrate. Zernik2 effected a n improvement in t h e method by carrying out t h e precipitation in a saturated solution of potassium nitrate, b u t even so allowance h a d to be made for traces of antipyrin-mercuric nitrate, which still persisted in t h e recovered caffeine. T h e procedure on which our experimental work is based h a d its inception in a s t u d y of t h e behavior of antipyrin toward iodin,3 its preliminary formulation having been dictated by t h e following considerations. Like m a n y basic substances, antipyrin yields in aqueous-acid media with iodized potassium iodide one or several iodin addition products or periodides, according t o t h e conditions of t h e e ~ p e r i m e n t . ~I n t h e presence of a substance like sodium acetate, however, or better sodium bicarbonate, t h e additive tendency of t h e halogen is immediately followed b y one of substitution, t h e final result being t h a t t h e antipyrin is quantitatively converted into its monoiodo derivative. On discharging t h e iodin excess with thiosulfate, we have in t h e resulting menstruum monoiodoantipyrin, which can be readily isolated a n d weighed. I n t h e event t h a t caffeine also is present during such treatment i t will be found unchanged a n d in admixture with t h e recovered iodoantipyrin. Determination of iodin in t h e composite residue t h u s obtained supplements all t h e d a t a required for t h e calculation of both caffeine a n d antipyrin. T h e procedure as finally adopted for t h e separation proper is embodied in t h e following essential operations: MET H 0 D
Transfer to a ~ j cc. o separatory funnel (Squibb type), b y means of t w o 5 cc. portions alcohol-free chloroform followed b y IO cc. water, a b o u t 0.2; g. of t h e caffeine-antipyrin mixture, a d d I g. sodium bicarbonate a n d 10-15 cc. 0.2 N iodin (or double t h e quantity of 0.1 N iodin), t h e latter reagent being added in successive small portions a n d t h e liquid mixture vigorously shaken 15-20 seconds after each addition. When all the iodin has been t h u s added, a decided excess of this reagent should be apparent in t h e liquid after a final vigorous shaking of I minute, in which event all t h e antipyrin will have been converted into t h e monoiodo derivative. If, however, all t h e iodin previously applied should appear t o h a v e been expended, a little more must be added t o insure excess a n d t h e mixture again shaken. Now discharge t h e uncombined iodin b y means of a small crystal of sodium thiosulfate, a d d 15 cc. redistilled U. S. P. chloroform, t h e n shake vigorously I minute. After clearing, draw 1 2
4
Apoth Ztg., 2 1 (1906), 674. Ibrd.. 21 (1906). 686 Cf. THISJOURNAL, 6 (19141, 7 5 1 A paper on the periodides of antipyrin is in course of preparation.
Vol. 7 , No. 6
off t h e solvent into a second separator containing j cc. water, shake a n d after clearing pass the chlorof o r m through a small, d r y filter into a tared j o cc. beaker and evaporate t o apparent dryness on the s t e a m bath, accelerating the operation b y means of a n air blast. Repeat t h e extraction with t w o (three, in case 0.1 N iodin is used) 2 5 cc. portions of chloroform, washing, filtering a n d evaporating each portion in rotation substantially as directed in t h e first instance. Recover all crystalline products separating about t h e tips of separator, funnel a n d edge of filter by judicious washing with chloroform. D r y t h e nearly colorless crystalline residue of caffeine a n d iodoantipyrin onehalf hour a t IojO, then cool a n d weigh. Designate this weight “A”. Dissolve t h e composite residue of caffeine and iodoantipyrin in 5 cc. glacial acetic acid, a d d I O cc. saturated aqueous solution of sulfur dioxide, t h e n transfer t h e resultant liquid b y diluting, pouring a n d rinsing with hot water t o a 400-500 cc. beaker until the final volume amounts t o about 2 0 0 cc. Add aqueous silver nitrate solution (about 0.3 g. silver nitrate), sufficient a t least t o precipitate all the, halogen, a n d follow with a few drops of nitric acid, then heat nearly t o boiling, stirring t h e while in order t o agglomerate t h e silver iodide. Add about 15 cc. concentrated nitric acid, cover t h e beaker with a watch glass a n d boil gently j or 6 minutes. Filter b y decantation through a tared Gooch, washing the precipitate once with a little alcohol, then with two I O O cc. portions boiling water, finally transferring t h e silver iodide completely t o t h e crucible. Wash several times with hot water a n d then with alcohol t o remove all traces of organic matter. Dry one-half hour in t h e air b a t h a t IIO’, cool a n d weigh. T h e weight of silver iodide multiplied b y the factor 0.8012 yields t h e quantity of antipyrin present in the sample taken. The quantity of caffeine is ascertained by subtracting t h e product obtained b y multiplying t h e weight of silver iodide b y t h e factor 1.3374, from t h e weight of t h e composite residue “ A ” . I n practice, the preliminary or gross separation of the caffeine-antipyrin mixture from the usual excipients of tablet a n d pill combinations is most conveniently effected b y extraction of t h e finely powdered mass on a tared filter with chloroform, this solvent together with its attendant alcohol being subsequently completely expelled first by gentle distillation a n d finally by evaporation on t h e steam b a t h , prior t o proceeding with t h e separation proper. Likewise in t h e case of alcoholic preparations containifig caffeine a n d antipyrin as essential ingredients, t h e recovery of these t w o substances is best carried out after evaporation of t h e alcohol on t h e steam bath. T h e residual menstruum is thereupon exhausted with chloroform in t h e usual way, t h e resulting solution of caffeine a n d antipyrin being treated precisely like the one obtained from tablet or pill combinations. T h e use of alcohol-free chloroform in connection with t h e halogenation of antipyrin is necessary in order t o preclude t h e possible formation of iodoform, the pres-
June,
1915
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
SERIES1 SILVERIODIDE IODIN (per cent) IODOANTIPYRIN Gram Recovery Theory Gram 40.47 40.40 0.2000 0.1498 40.34 40.40 0.3000 0.2240 ANTIPYRIN Gram 0.2500 0.2500 0.2500 0.3000
Caffeine Antipyrin Gram Gram 0.2000 0.0500 0.0500 0.2000 0.2000 0.0500 0.2000 0.0500 0.0500 0.2000 0.0500 0.2000 0.0500 0.2000 0.0500 0.2000 0.0500 0.2000 0.0500 0.2500 0.0500 0.2500 0.0500 0.2500 0.0500 0.2500 0.0500 0.2500 0.0500 0.2500 0.2592 0.0648 0.2592 0.0648 0.1000 0.1000 0.2500 0.1667 0.1667 0.2500 0.2500 0.1667
SERIES 2 SILVER IODIDE ANTIPYRINRECOVBRY Gram Gram Per cent 0.2496 99.84 0.3115 0.3111 0.2493 99.72 0.2503 100.12 0.3124 0.3731 0.2989 99.63 SERIES3 RECOVERY Residue Antipyrin “A” A d Caffeine Per Gram Gram Per cent Gram cent Gram 0.3836 0.2495 0.0499 99.8 0.1999 99.9 0.0507 101.4 0.3837 0.2490 0.1995 99.7 0.3837 0.2494 0.OSOl io012 0.1999 99.9 0.3845 0.2492 0.1997 0.0512 102.4 99.8 0.2490 0.1995 0.0514 102.8 99.7 0.3844 0.3834 0.2494 0.1998 0.0499 99.8 99.9 99.7 0.3835 0.2489 0.1994 0.0506 101.2 0.3837 0.2500 0.2003 100.1 0.0497 99.4 0,3839 0.2486 0.1994 0.0514 102.8 99.7 0.3107 0.0503 100.6 99.5 0.4658 0.2489 0.3118 0.2498 0.0502 100.4 99.9 0.4672 0.3120 0.2500 100.0 0.0513 102.6 0.4686 0.0509 101.8 0.4674 0.3114 0.2495 99.8 98.6 0.4657 0.3116 0.2497 0.0493 99.9 99.6 0.4661 0.3115 0.2496 0.0498 99.8 0.3237 0.2593 100.0 0.0649 100.2 0.4976 0.4976 0.3236 0.2593 100.0 0.0648 100.0 99.8 0.2654 0.1238 0.0992 0.0998 99.2 99.9 0.5864 0.3138 0.2514 100.5 0.1666 0.3124 0.2503 100.1 0.1648 98.8 0.5824 0.1677 100.6 99.5 0.5831 0.3107 0.2489
ence of which in t h e composite residue “A” would naturally vitiate the analytical findings. T h e application of iodin in small portions appears t o favor the production of a purer iodoantipyrin t h a n is t h e ease when this reagent is all added a t one time, as evidenced by t h e color of t h e caffeine-antipyrin residue. I n order t o free t h e latter from all contaminating vdatile products under t h e conditions outlined in the method, particular attention should be given t o t h e actual working conditions of the drying oven,’ since incomplete or improper desiccation must necessarily lead t o widely divergent caffeine values, while heating a t temperatures materially higher t h a n I o j o is found to exert a n unfavorable influence on the recovery of both caffeine a n d antipyrin. T h e color changes following the addition of strong nitric acid are quite characteristic, passing from colorless through deep red t o pale yellow in the course of 5 minutes’ boiling. I n view of this somewhat radical treatment t o which the caffeine is likewise subjected, any direct determination of this substance becomes impractical. The quantity of caffeine is therefore ascertained indirectly with a reasonable degree of accuracy by subtracting t h e weight of iodoantipyrin (calculated) from t h a t of the composite residue “A”. As aIready indicated, t h e determination of antipyrin is effected b y estimating the halogen contained in the iodo derivative a n d calculating t o the parent substance. Considerable experimentation was required before a suitable procedure could be found for the quantitative withdrawal of iodin from the pyrazolon complex. Treatment by Carius naturally gave very accurate returns b u t in point of facility was far from satisfactory. T h e well-known methods depending on the action on the one hand of alcoholic potash a n d on t h e other of metallic sodium a n d alcohol both failed completely in the object sought. Even direct I
CI. Lorin H. Bailey,
THISJOURNAL, 6 (1914). 585.
j21
a n d continued boiling with a n aqueous acid solution of silver nitrate gave little better results. Thus, in two determinations carried out under slightly varying conditions, only 35.28 a n d 3 7 . 8 2 per cent iodin could be recovered as silver iodide, the theory demanding 40.40 per cent. A very effective a n d convenient reagent was finally discovered in sulfur dioxide, which rather unexpectedly perhaps yet none t h e less completely removes the substituted iodin, as evidenced by numerous controls. EXPERIMENTAL
T h e data given for Series I , 2 a n d 3 are representative of results obtained b y t h e authors in operations carried out substantially in accordance with the procedure outlined above. Experiments bearing directly on the behavior of caffeine a n d iodoantipyrin, when heated alone a n d in admixture a t 1 0 5 O a n d under conditions comparable with those followed in the regular method, indicate t h a t loss by volatilization is mainly chargeable t o caffeine, as will appear from a n examination of the following results. The several charges were first dissolved in 2 j cc. chloroform a,nd the solvent then blasted off at a moderate heat prior to treatment in the drying oven. WEIGHT AFTER HEATING ALONE Initial wt. 30 min. 30 min. 1 hr. Total loss Caffeine 0.1000 0 0993 0.0990 0.0980 0.0020 Iodoantipyrin 0.4000 0 4005 0.4003 0.4001 CafIodoanWEIGHTSAFTER Total IN ADMIXTURE loss feine tipyrin SUCCESSIVE HEATINGS 0.0500 0.4000 0.4494 0.4491 0.4478 0.4464 0.4454 0.4431 0.0069 0.1000 0.4000 0.4995 0.4992 0.4981 0.4963 0.4951 0.4926 0.0074 0.2000 0.4000 0.5996 0.5991 0.5978 0.5963 0.5954 0.5922 0.0078
___
Iodin determinations in the three composite residues were made with the following results: IODOANTIPYRIN RESIDUE AgI Gram Gram Gram Per cent 0.4431 0.2989 0.3997 99.92 0.4926 0.2986 0.3993 99.82 0.5922 0.2985 0.3992 99.80 SYNTHETIC PRODUCTS LABORATORY, BUREAUOB CHEMISTRY DEPARTMENT OF AGRICULTURE, WASHINGTON
THE DETERMINATION OF NITRIC NITROGEN IN SOILS By E. R. ALLEN Received February 9, 1915
O B J E C T O F T H E RESEARCH-The determination O f nitric nitrogen has been t h e subject of a very large amount of experimentation, discussion a n d controversy. In spite of the array af methods t h a t have been proposed, more or less uncertainty exists in t h e use of any one of t h e m , as is shown, for instance, by the following statements: ‘ ‘ N o single method appears t o be applicable t o the determination of nitrogen in nitrates in all classes of water, sewages a n d sewage effluents, a n d there is no method which is not subject t o considerable error;”l and, “ T h e accurate determination of nitric acid in combination presents great difficulties, a n d can be made only by indirect means; the methods here given are sufficient for most purposes. T’ery few of t h e m can be said t o be simple, but it is t o be feared t h a t no simple process can ever be obtained for t h e determination of nitric acid in many of its combinations.”2 1 “Standard Methods of Water Analysis,” Amer. Pub. Health Assoc , p. 23 (1912). 2 Sutton. “Volumetric Analysis.” 10th Ed., p. 271 (1910).
