ANALYTICAL EDITION
210
Vol. 3, No. 2
Method for Identification of the Common Gums’ Morris B. Jacobs and Leon Jaffe DEPARTMENT OF HEALTH, 505 PEARLST., NEWYORK, N. Y
may be seen at a glance. not as yet been investigated although there is a growing need for methods for their identification. They have, of course, some properties which distinguish them from like substances and consequently enable them to be detected. This paper gives the results of an investigation of these properties. For the sake not only of completeness but also of usefulness, the tests for the older known gums have been included, and many new ones which our investigation has disclosed have been added. An analytical method for the identification of these gums has also been developed. The few methods for the separation of gums from foods, drugs, cosmetics, etc., that are found in the literature are of little value and do not lend themselves to use for identification purposes. That of Cook and Woodman (2) was used by the authors in some cases. The methods proposed are all rapid methods and involve no need of hydrolysis of the gum and then subsequent identification of the hydrolysis products, a procedure which, for a commercial laboratory, where these methods will probably find their greatest use, is too long-winded and thus of no practical value. Patrick (3) proposed a method for the detection of thickeners in ice cream, satisfactory for the detection of thickeners as a group, but not providing for identification. The use of hydrochloric acid in this method, to dissolve excess milk proteins, interferes with the characteristic reactions of the gums. Cook and Woodman (2) give a method not only for the separation of gums but also for the identification of some of them by an alcohol-precipitation method. Theirs has the disadvantage of the use of tannic acid as a precipitant for the protein bodies in the product from which the gum is being extracted, which not only precipitates the proteins but some part of the gums as well. For example, it precipitates locust kernel, quince seed, and Hull emulsifier. Weinberger and Jacobs (6) published a method for the identification of gums by means of a characteristic alcohol precipitate. This method is in itself insufficient to identify some of them positively and does not include some of the newer gum products. Congdon’s method (I), as pointed out by Cook and Woodman, is practically useless because the tests are applied without prior separation of the gums, and consequently the tests are often performed on impurities in the gums. Furthermore, if the gum happens to be incorporated in a food, drug, or cosmetic, the characteristic reactions may be entirely masked. Revis and Bolton (4) give a method for the separation and detection of agar-agar which is in reality a general one for the detection of gums as a group rather than for agar-agar alone because they rely on the jellying action of a concentrated solution of agar as the test. The gums may be extracted from foods, drugs, and like substances by the method either of Patrick or of Cook 1 Received
December 8, 1930.
of 10 per cent acetic acid for every 50 cc. of sample, heat to boiling, and add 3 teaspoonfuls of kieselguhr for every 50 cc. of the sample. Filter on a plaited filter and discard the precipitate. Precipitate the gum from the filtrate by the addition of 12 cc. of 95 per cent alcohol for every 3 cc. of the filtrate. Add 3 cc. of a mixture of 95 cc. of 95 per cent alcohol and 5 cc. of concentrated hydrochloric acid. The acidified alcohol completely dissolves the milk proteins. At this point the authors centrifuged and filtered the alcohol solution containing the precipitated gum, washed the gum with 95 per cent alcohol to free it from the acid, and then allowed the gum to dry spontaneously before applying qualitative tests for its identification. I n the Cook and Woodman (2) method, dilute the sample to a suitable concentration with water. Add 5 cc. of dilute acetic acid and 25 cc. of 10 per cent tannin solution, heat the mixture for 20 to 30 minutes, centrifuge, filter, and discard the precipitate. Add 40 to 50 cc. more of tannin solution, heat for a short time, centrifuge, and filter. Again discard the precipitate. Treat the filtrate with twice its volume of acetone. Centrifuge and filter, and discard the filtrate. Dissolve the precipitate in 50 cc. of warm water slightly acidified with acetic acid, and then add 10 cc. of ammonia (sp. gr. 0.90), centrifuge, and filter. Add acetic acid to the a t r a t e until slightly acid and precipitate the gum with 95 per cent alcohol. At this point the authors centrifuged, filtered, and washed the precipitate with 95 per cent alcohol, and then allowed the gum to dry spontaneously before making qualitative tests. GUM
Table I-Materials Used No. AND FORM TEST OF SAMPLES SOLN.
MANNER OF SOLUTION
% Arabic: acacia, arabin 1 3 Tragacanth: bassorin, 2
tragacanthin
Agar-agar
2
Karaya: Indian gum
1 1
Irish moss: algin
2
Quince seed
2
Locust kernel: locust bean, galagum, Iactox
6 1
Hull emulsifier
1
Powder Lump Powder
1
Goes readily into clear s o h
Swells when placed in water and forms translucent somewhat viscous soln. which becomes ropy on standing Strip form 0.5 Goes into soln. on warming and on cooling forms gel ’ Powder 1 Not very soluble in water. Lump Particles swell and form layer at bottom of container Seaweed 0.5 Translucent, viscous, yelapprox. lowish s o h Seed 1 Opalescent soh. and stringy precipitate on standing 1 Does notconsiderably form a clearformsoh. Powder Swells Extracted ing opaque colloidal soh. from a food from which flocculent precipitate settles on standine . Powder 1 Not very soluble. Particles swell and remain at bottom like Indian 1
gum
In products which contain no alcohol-insolublesubstances, such as proteins, dextrins, etc., other than gums, it is best
April 15, 1931
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
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to precipitate the gums directly. If the sample be liquid, merely add the requisite amount of 95 per cent alcohol. If it be solid, add a suitable amount of water, make slightly acid with acetic acid, boil, and filter. Precipitate the gums from the filtrate with 95 per cent alcohol. Procedure
A list of the gums tested, together with their manner of dissolving in water, is given in Table I. For Irish moss, locust kernel, quince seed, tragacanth, and karaya, a Cook and Woodman extraction of the original test solution and a new test solution were made with the precipitate from the alcohol treatment. These solutions were then subjected to the same tests. They gave corresponding results. The reagents used were c. P. materials and were made according to directions given in standard texts such as the U. S. Pharmacopeia, the methods of the A. 0. A. C., Cohen's Organic Chemistry, etc. The procedure was, in general, to add 2 or 3 drops of the reagent to 5 cc. of the test solution, note the result, and then add an excess of the reagent. In the case of potassium hydroxide, sulfuric acid, phosphoric acid, hydrochloric acid, Schweitzer's reagent, and neutral ferric chloride, a few drops of the reagent were added to the test solution and the mixture then boiled. Then an excess of the reagent was added and again the mixture was boiled. I n the case of Schiff's reagent, the test solution was boiled first and then the reagent added. I n each case for this reagent a pink coloration was obtained. This is to be disregarded and only a precipitate formation noticed. For the tannic acid test, dilute acetic acid must be added to the test solution first, and then the reagent added. For the alcohol precipitate, the method of Weinberger and Jacobs was used. For every test, a blank or control must be used in order to distinguish any change in the test solution due to the addition of the reagent. The results of these tests are given in Table 11. In order to make use of the table properly, care must be taken to notice the distinguishing characteristics of the precipitate formed. That is, whether it is voluminous, flocculent, small flocculent, stringy, powdery, curdy, filamentous, etc. With certain reagents there is no apparent change, hence the use of blanks and controls is essential. The word "gel" in the table indicates an actual jellied condition. When we use the word "gelatinizes" we imply that the mixture has been thickened. These are clear distinctions and are readily noticeable in making the tests. It will be seen from the above that the table is a means of distinguishing one gum from another. An outline method for the identification of the gums dealt with in this paper, using two reagents and a t the most three, is given below. The procedure is as follows: Take 3 cc. of the unknown test solution, add 0.5 cc. of Millon's reagent, and after 5 minutes note the result. This will divide the gums into four groups. Note the group to which the unknown belongs, and again take 3 cc. of the test solution and add the group reagent. This will distinguish the gum. Then make any of the verification tests on 3 cc. of the test solution again, if necessary.
J
The unknown may be arabic, tragacanth, agar, karaya, Irish moss, quince seed, locust kernel, or Hull emulsifier. To 3 cc. of unknown test soln. add 0.5 cc. of Millon's reagent:
8
GROVP1 Gelatinizes
Irish moss Agar Locust kernel
GROUP2 Vol. floc. ppt., does not settle
GROUP3 Stringy ppt., settles
GROUP4 Powdery or fine curdy ppt.
Quince seed Tragacanth
Hull emul. Galagum
Arabic Karaya
T o 3 cc. of the unknown test soh. add group reagerlt:
ANALYTICAL EDITION
212 GROUP1 Add borax, 4% Locust kernel gels Others neg.
GROUP2 Add KOH Tragacanth, bright yellow Quince seed, stringy ppt.
GROUP3 GROUP4 Add borax, 4% Add phosphoric acid Galagum gels Hull emul. aissolves Schweitzer’s reagent
K~~~~~ turns pink Arabic dissolves in excess of Millon’s reagent
To 3 cc. of test soh. add KOH:
Vol. 3, No. 2
Locust bean may be distinguished from locust kernel by the addition of iodine solution. The former is colored purplish. Galagum may be distinguished from both of these by the stringy precipitate With Millon’s reagent. Each gum has its own peculiar method of going into solution in water. This peculiarity may be sufficient, if one often works with gums, to give an index as to the gum.
Irish moss gels, Agar s o h . clarifies
Acknowledgment
Notes Indian gum will give a pink coloration when boiled with either phosphoric or hydrochloric acid. When allowed to stand in either solid or solution form, karaya develops an acetic acid odor. Quince seed will give a stringy precipitate, which rises to the top with Schiff’s reagent. Hull emulsifier is rendered completely soluble by boiling with potassium hydroxide. Agar-agar solution is clarified by boiling with concentrated sulfuric acid. Irish moss smells like seaweed and is jelled by. potassium hydroxide. Tragacanth gives a bright yellow solution and stringy precipitate when boiled with potassium hydroxide solution.
The authors wish to thank Walter Weinberger for the use of some of his data in the above work. This work was done in the laboratories of the Department of Health of New York City. Literature Cited (1) Congdon, J. IND. END.CHEM.,7, 606 (1915). (2) Cook and Woodman, Ibid., 10, 630 (1918). (3) Patrick, U.S.Dept. Agr., Bur. Chem., BuZZ. 116, 26 (1914). (4) Revis and Bolton, “Allen’s Commercial Organic Analysis,” Vol. VIII, p. 193, Blakiston, 1914. (6) Weinberger and Jacobs, J . Am. Pharrn. Assocn., 18,34 (1929).
Accurate Air Separator for Fine Powders‘ Paul S. Roller NONMETALLIC MINERALS EXPERIMENT STATION, U. S. BUREAUOF MINES,N s w BRUNSWICK, N. J.
An apparatus is described for separating quantitaPortland cement, considerHE properties of microtively a 1-kg. charge of fine powder into a series of able quantities of each of the scopic powders2 are vaTious fractions were refractions beginning 0-2.5 microns in size. Except for greatly dependent on quired. It was decided to ret h e finest fractions, at or below 5 microns, where attheir mean particle size and construct the air a n a l y z e r trition by the air current takes place in t h e case of soft distribution of sizes. An air powders, the particle sizes separated are very homopreviously described so that analyzer has been described geneous within the limits given by Stokes’ law. a large amount of maherial (6)for determining the percould be started with, thus Several causes affect the rate of separation, b u t the centage in a microscopic conveniently p e r m i t t i n g a most important is that of t h e rate of air flow. Under powder of the successivefracsimilar conditions t h e rate of separation is proportional large air flow and consequent tionsS 0-5, 5-10, 10-20, 20rapid rate of separation. t o t h e air flow. Depending on the latter, initial rates of 40,40-60, and > 60 microns. separation of the particle-size fractions have been made This apparatus operated on a Description of Apparatus up to 135 grams per hour at a flow of 140 liters per minsample of between 25 and 30 ute. grams. I n basing the design of the Continuous separation can be effected by t h e use of For rapidity and accuracy s e p a r a t o r on the air anaan offset separator tube with separate collection of the in analyzing a microscopic lyzer; it was p a r t i c u l a r l y oversize. At a 30-micron particle size cut of a Portland powder for its distribution desired to duplicate the selfcement powder, with an air flow of 500 liters per minute, of p a r t i c l e sizes, such a c i r c u l a t i o n of the powder t h e equivalent rate of feed was 5.4 kg. per hour, while small sample is d e s i r a b l e . charge as illustrated in Figt h e rate of recovery was 0.92 kg. per hour. The efficiency H o w e v e r , n u m e r o u s inure 1. This figure shows that of recovery, based on the maximum possible recovery s t a n c e s a r i s e when large the particles composing the in a run, was not in excess of 28 per cent. q u a n t i t i e s of each of the Dowder charge circulate in a Darticle-size f r a c t i o n s are clockwise dGection; a t the wanted in order to determine their particular physical and same time, the whole mass builds up in a direction opchemical properties; one may also require large quantities posite that of the incoming air. Thus the powder charge is below a minimum particle size of, for example, 30 microns. adequately prepared for the air separation. It was soon found In order to study further the properties of fine particles with the larger apparatus that the condition of self-circulation of natural anhydrite in connection with the retardation of of the powder charge was easily attained. Figure 2 is a photograph and Figure 3 a drawing of the air * Received January 20, 1931. Published by permission of the Director, separator which has been successfully operated over a long U. S. Bureau of Mines, and not subject to copyright. * A microscopic powder is defined as that portion passing through the period of time. Container C holds about 1 kg. of powder charge. It is a 200-mesh sieve. In making an analysis into six fractions, it has subsequently been found standard 7.6-cm. (3-inch) iron U-bend, with a radius of that there is no loss of accuracy, but rather that the time required may be 11.4 cm. (41/2 inches). At the bottom is a plug for emptying very considerably reduced by using the same separator tube for the 10this container conveniently. The hard rubber cam shown micron as for the 5-micron separation. The smaller separator tubes are in the figure rotates a t about 300 r. p. m. and operates against then employed at the higher rate of air flow for the successive fractions beginning 20 microns. Opportunity is also taken to remark on the microa ball-bearing bicycle hub that is fastened to container C. scopic examination of the fractions. It has been found time-saving and The rotation of the cam causes C to oscillate about the bearing more e5cient to conclude the dry dispersion of the grains with a grounded B. The lug L is riveted to C, and on the upward stroke rises platinum wire as described by a similar wet dispersion after the addition about 1 cm. The downward stroke is accelerated by spring of a drop of liquid.
T
