Fluorescence of Rubber and of Compounding Ingredients Y. N. MORRIS, Firestone Tire & Rubber Company, Akron, Ohio appearance of optimum tensile URING the past few The color of the fluorescent light (if any) strength. This paper of Bruni’s years considerable inemitted by various rubber compounding indoes not seem thus far to have terest has been manigredients when exposed to ultra-violet light has been published. fested in the fluorescence exbeen observed. M a n y antioxidants, softeners, The primary objects of the hibited by many s u b s t a n c e s and accelerators exhibit fluorescence, whereas, of present paper are (1) to provide when exposed to u 1t r a - v i o 1e t information regarding the fluolight. Krahl (9) seems to have th-. inorganic pigments examined, only zinc oxide rescent colors of antioxidants, been the first to point out the shows a characteristic effect. The fluorescent softeners, accelerators, and inpossible value of this phenomecolors of various commercial brands of zinc organic pigments, with special non to rubber technologists. I n oxide permit them to be distinguished f r o m one reference to products of Amerian article devoted primarily to another. Particle size is found to govern the can manufacture; (2) to supplethe effect of ultra-violet light ment the information previously on the aging of rubber, he menfluorescent colors of a series of zinc oxides all published with respect to the tioned that many accelerators, made from the same original material. After fluorescent colors of zinc oxides antioxidants, and oils give charlow-temperature ashing of rubber stocks (conand show results bearing on the acteristic fluorescent colors when taining various zinc oxides), it is possible to question of the cause of the difexposed to ultra-violet light from identify the zinc oxide used, provided it has a ference b e t w e e n various zinc which all or nearly all of the oxides; and (3) to show the revisible light has been removed by sqficiently characteristic fluorescent color. Welllation between the intensity of means of a suitable glass filter. vulcanized rubber shows a yellow fluorescent color fluorescence and the state of Within the past five or six years of fairly strong intensity, while decidedly undercure of c e r t a i n r u b b e r comseveral other European workers cured rubber fluoresces but slightly. I n general, pounds. have investigated one or more no definiie relation between optimum physical phases of the application of filtered ultra-violet light to the properties and the intensity of fluorescence is APPARATUS problems of the rubber industry. apparent. Rubber loses its capacity for fluorescCertain s u b s t a n c e s , w h e n Zinc oxides and accelerators ing almost completely upon being exposed to seem to have constituted the stimulated by the absorption of direct sunlight f o r one hour. major interests of those who light of certain wave lengths, have entered this field. Thus will emit light of greater wave Nagle (II), using a 460-volt mercury arc lamp and a Chance’s lengths. This phenomenon is called fliorescence. It can screen (which filtered out all the visible light except very small be explained briefly as the result of the absorption of incident portions of the extreme violet and the extreme red), showed waves which, by a modified resonance action, cause a reemisthat eight different samples of zinc oxide gave eight different sion of light of longer wave lengths. To obtain the most fluorescent colors. Kirchhof (7), who made a somewhat simi- striking fluorescent effects, it is necessary to use incident lar comparison of five different zinc oxides, :Ittributed the light which is not visible to the human eye-i. e., ultra-violet differences in fluorescence largely to the impurities present. light. If the samples are exposed to ultra-violet light in a Kirchhof also listed the fluorescent colors of a number of ac- dark room, the only light which registers on the eye is that celerators, of several of the common pigments, and of the resulting from the fluorescence of the substances under examimaxy constituents from various rubbers. Most of the twenty nation. Since an adequate source of ultra-violet light free accelerators examined by Ditmar and Dietsch (5) exhibited from visible light is not available, it is necessary to exclude the characteristic fluorescent effects, which were evident even visible light by means of a filter. when the accelerators were mixed with pale crepe. Ditmar Although carbon arc lamps were tried during the early (4) later reported that samples of mercaptobenaothiazole from stages of this work, the most satisfactory source of light availthree different manufacturers showed different fluorescent able was a 250-volt Cooper-Hewitt mercury vapor lamp. A colors. In this same article he also described the fluorescence metal bottom provided with a small window for insertion of of several antioxidants. The most comprehensive comparison the glass filter was attached to the cover furnished with this of accelerators thus far reported is that of Kojima and Nagai lamp. Since this cover was not entirely light-tight, it was (8), who examined the solutions of forty-one different ac- wrapped in a piece of heavy, dark cloth, containing an opencelerators. Most of them were found to fluoresce in a char- ing corresponding to the window in the bottom of the coveracteristic manner. ing. Another field which has received some slight attention is that Although certain other investigators have stated (without of the influence of the state of vulcanization on the fluores- furnishing confirmatory data) that the filters which they used cence of a given rubber compound. Krahl (9) showed that transmitted no visible light at all, none of the three filters the fluorescent colors of certain stocks (of unreported composi- tested during the present work excluded all of the visible tion) were different in the unvulcanized, undervulcanized, light. The filters tried were the red-purple Corex A of the and overvulcanized states. Bruni (3) later presented a paper Corning Glass Works of this country, the UG-1 filter of the in which he stated that, as cure progresses, there appears a Jena Glass Works of Germany, and a filter furnished by Kelcorrelation between the advent of strong fluorescence and the vin, Bottomly, and Baird of England. Curves showing the 107
D
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
108
percentage transmission‘ of light of various wave lengths by these filters are presented in Figure 1. Although the border lines of the visible spectrum cannot be definitely given, it is apparent that these filters tend to transmit a little light at both ends of the visible spectrum. As the filter from Kelvin, Bottomly, and Baird transmits much ultra-violet and but little visible light, and some of the most satisfactory results were obtained by its use, it was employed exclusively during the observations of fluorescent colors reported here. FLUORESCENCE O F +kCCELERATORS, SOFTENERS, .4ND ANTIOXIDANTS
For the examination of accelerators or other dry powders, small samples were placed on a glass plate and pressed down with a spatula so as to present a fairly smooth upper surface. It was observed that differences in the fluorescent colors
Vol. 26, No. 1
Many of the products which are white or nearly so in daylight appeared as some shade of purple during these tests. It is thought that this coloration is to be attributed primarily to the visible light leaking through the filter rather than to fluorescence. The variations in the exact shades and tints of purple observed may have been occasioned in part by fluorescent effects of rather low intensity. Table I1 shows the fluorescent colors exhibited by several softeners commonly used in the rubber industry. It was observed that the fluorescent colors of the softeners are lighter and more intense than the natural colors in many cases. TABLE11. FLUORESCENCE OF SOFTENERS SOFTENERS Pine tar Refined asphalt Stearic acid Mineral rubber Rosin oil Rosin .Mineral oil (medium process)
FLUORESCENT COLOR Dark yellow-green Dark yellow-brown Light bluish violet Purple (appears nearly black) Light blue Intense light blue Very light blue
The fluorescent color has been used in this laboratory in confirming the identity of softeners extracted from products of unknown composition. A series of results obtained with commercial antioxidants is shown in Table 111. The fluorescent effects with these products were often quite pronounced, as evidenced by the designation “glowing” in certain cases. TABLE111. FLUORESCEXCE OF ANTIOXIDANTS ANTIOXIDANT Acetaldehyde aniline (VGB) N,N’-Diphenylenediamine (Stabiljte) Hydroquinone Condensation product of aniline and a ketone (Flectol) Aldol-a-naphthylamine (Agerite Resin) Phenyl-&naphthylamine (Agerite Powder) Phenyl-@-naphthylamine (Neosone D) Phenyl-a-naphthylamine (Neorone A) Phenyl-a-naphthyhmine (92.5%) and m-toluylenediam~ne(7.5%) (Neorone C) ~
could be best discerned after the samples had been exposed long enough so that the eye had adjusted itself to the dark surroundings and the lamp had become somewhat heated. The fluorescent colors were recorded immediately after the observations had been made and the room had again been illuminated. It should be kept in mind that the personal element in the recording of the observations made is very great, and that the colors shown in the tables are indicative only of the general nature of the fluorescent effects. For any exact comparisons or for the determination of the nature of a n accelerator of unknown composition, standard samples should be available for direct comparison with the unknown. The results obtained with a number of accelerators of American origin are shown in Table I. TABLEI. FLCORESCENCE OF ACCELERATORS .kCCELERATOR Dizo-tolylguanidine (D. 0. Phenyl-o-tolylguanidine Diphenylguanidine and 2,4-dinitrobenzothiazyl sulfide (Ureka) 2,4-Din1trobenrothiazyl sulfide Tetramethylthiurarn monosulfide (Monex)
FLUORESCENT COLOR“ Muddy gray Light purple Purple Light bluish purple Reddish black Appears black Appears black (trace of purple) Deep purple Reddish brown Light brown Purple Light purple Dark yellowish green
Tetramethylthiuram disulfide (Tuads) 2-Mercaptobenzothiazole (Captax) Ethylidene aniline (Vulcone) Thiocarbanilide Hexamethylenetetramine Triethyltrimethylenetriamine (Trimene Base) Triethvltrimethvlenetrirtmine and stearic acid (Trimene) Light green Zinc butylxanthate Very deep purple Zinc dimethyldithiocarbamate (Zimate) Dirty purple Piperidinium pentamethylenedithiocarbamate Appears black (du Pont No. 552) Carbon diaulfide derivative of .methylene diAppears black piperidine 5 % oleic acid (Pipsol-X) * Samples appearing black obviously show neithe? ysible fluorescence nor reflection; samples showing a purple color are exhibiting reflection with little or no fluorescence.
+
1
The data were obtained from the manufacturers.
COLORIN DAYLIQHT Tan Straw
FLUORlSCnNr COLOR Dull greenish brown Red-violet
White Dark brown
Blue-violet Greenish yellow
Reddish brown
Dull brownish green
L i g h t brown- Light blue (glowing) gray Faintlygrayish Light b l u e - v i o l e t pink (glowing) Light blue (glowing) Purplish pink Chocolate
Di-8-naphthyl-p-phenylenediamine Brownish white (Agerite White)
Violet (glowing) Light blue
At a later date, certain of these products were observed again, as were also some samples of other materials known to have the properties of antioxidants. I n order to draw more definite distinctions between the various phenylnaphthylamines, an attempt was made to describe the fluorescent colors in terms of the color standards of Mulliken (IO). According to this system, the color of Neozone D approximated blueviolet-tint 1, whereas that of Agerite Powder was bluetint 2. Although it is conceivable that the use of a set of standards of this type might be of considerable value during a more exacting investigation, no further use was made of them in the present study.
FLUORESCENCE OF ZIXC OXIDES AND OTHER INORGANIC SUBSTANCES The procedure used in the examination of zinc oxides was the same as that employed with accelerators. The results of the comparison of nine different samples of zinc oxide are shown in Table IV. Obviously it was not difficult to distinguish these various samples of zinc oxide from one another. When zinc oxide-rubber mixes, containing 2 per cent of the pigment, were examined under filtered ultra-violet light, it was found that the only mixes which could be distinguished were those containing zinc oxides of appreciably different fluorescing properties. Thus XX-red could be distinguished from Kadox, but not from other products which exhibited fluorescent colors that were predominantly brown. Since
January, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
Nagle (11) reported somewhat greater success in distinguishing mixtures of pale crepe with various zinc oxides, he must have been able to obtain more intense fluorescence as a consequence of using a stronger source of light (460-volt lamp) than that available for the work in this laboratory. TABLE
Iv. FLUORESCEXCE
GRADEOR SAMPLE TYPEOF OXIDE 1 Kadox 2 XX-Red-4 4
u. 5. P. u. s. P.
5
French process
6
Electric furnare proceas American process
3
OF ZISC
OXIDES
FLUORESCENT MANUFACTURER COLOR N. J. Zinc Co. Deep purple Light yellowish N. J. Zinc Co. brown N. J. Zinc Co. Light brownish purple Grayish green Int_ern. Lead Refining CO.
7 8
9
Aao ZZZ (paint grade) Chemically pure
Intern. Lead Refining co. St. Joseph Lead Co.
Brown tinged with purple Brownish purple
Intern. Lead Refining co.
Bright yellow tinged wir,h brown Lighr, yellow
Mallinckrodt Works
Dull gray
Am. Zinc Oxide Co.
Chem.
I n the next experiment a large number of more or less common compounding ingredients for rubber were examined. Of these, the following, which are all white or nearly white in daylight, showed only the purple color which is attributable primarily t o the visible light passing through the filter; whiting, aluminum flake, asbestine, catalpo clay, light magnesium carbonate, lithopone, blanc fixe, lime, barytes, and heavy magnesium oxide. Deviations from the normal shade of purple in the cases of lithopone, blanc fixe, barytes, and lime may have been due to some fluorescence. The following appeared black: iron oxide, crimson antimony, litharge, yellow ocher, vermilion red, and blue lead. Attention is directed to the fact that compounds of the heavy metals often appear black when exposed to filtered ultra-violet light. The fluorescent color of sulfur appeared t o be such a deep purple as to be nearly black, while that of ultramarine blue was a deep bluish purple. I n view of the fact, that the zinc oxides fluore>ce, whereas most of the other inorganic pigments tested do not, it was decided to examine certain other compounds of zinc and of other metals. Most of the zinc compounds were found t o fluoresce, an especially intense glowing effect being obtained with the carbonate (light purple), the oleate (light green), and the laurate (light blue-violet). Zinc chloride appeared light blue, zinc sulfide light yellowish orange, and the zinc salt of o-aminothiophenol only a dirty purple. In connection with the results obtained withazinc compounds, it is of interest that Kirchhof (7) has observed that the introduction of zinc into the molecule of a nonfluorescent substance often results in a product which fluoresces strongly. I n view of the results obtained in this laboratory, it is surprising that Beutel and Kutzelnigg ( I ) found no fluorescence in the case of zinc chloride and zinc carbonate. Compounds containing iron, lead, and chromium were among those n-hich appeared either black or a very dark purple when exposed to filtered ultra-violet light. Cadmium sulfide was found to show a deep red color. Cuprous cyanide exhibited a glowing violet color and mercurous chloride a bright orange. Since none of the cupric and mercuric compounds examined showed fluorescence, the present results tend to confirm the conclusion of Haitinger, Feigl, and Simon ( 6 ) that salts of metals in the lower state of oxidation show a more characteristic fluorescent effect than those of rnetals in the higher state. It is of interest that the most brilliant effect observed during this entire study was that obtained with uranyl acetate, which exhibited a glowing, light green color. A brief study was made of the possibility of identifying zinc oxides in vulcanized rubber compounds by igniting the
109
stocks and observing the fluorescent colors of the resulting samples of ash. I n the first test, vulcanized stocks containing 50 per cent by weight of four different zinc oxides (samples 1, 2, 5, and 7 of Table IV) were ignited and ashed in a muffle furnace. The ashed zinc oxides did not resemble the available standards and could not be identified. For instance, the ash from the stock containing Kadox was light in fluorescent color, whereas Kadox is normally a deep purple in fluorescent color. The ashing was conducted a t a lower temperature in the next test. Samples of the stocks were merely heated with a burner until the carbon was largely but not completely burned. Upon examining the four samples of ash, it was found that zinc oxides 1 and 7 (Table IV) could be distinguished from the other two samples and from each other, while 2 and 5 could not be distinguished from each other. A repetition of this test with a new set of rubber stocks yielded exactly the same results. The conclusion to be drawn is that the source of zinc oxides in rubber stocks of this type can be determined by ashing the stocks a t a carefully controlled temperature and examining the samples of ash under filtered ultra-violet light, provided the fluorescent colors of the zinc oxides concerned are not naturally too nearly alike. A stronger source of ultra-violet light might permit of better results. Since the results obtained as a consequence of ashing stocks containing Kadox suggested the possibility that particle size exerted an influence on fluorescence, it seemed that an evaluation of this possible effect would be of interest. A series of zinc oxides of varying particle size was made available by the New Jersey Zinc Company, in whose laboratory the measurements of particle size were made by the method of Stutz and Pfund (12). The samples were all prepared from the same original material by a process which insured that they would not vary in purity to any appreciable extent. The results of the observations of fluorescence are shown in Table V. TABLEV. EFFECTOF PARTICLE SIZEOF ZINC OXIDEON FLUORESCENT COLOR P l R T I C L E SIZE
Micron 0.182 0.191 0,203 0.217 0,290 0.334 0.403 0,800 Approx. 1.50
FLCORESCENT COLOR lfuddy gray' trace of brown Muddy gray' Muddy gray Muddy gray; trace of green Lieht brown Greenish gray Grayish green Greenish yellow Yellow
With the exception of that obtained with one sample, the fluorescent colors changed progressively from brownish gray through gray, greenish gray, grayish green, greenish yellow, to yellow. Xo explanation is apparent for the fact that the sample with particle size of 0.290 p exhibited a light brown color, which was decidedly different from that of the other samples. The results in general indicate that particle size may be fully as important a factor in governing differences in the fluorescent colors of zinc oxides as are the impurities present. I n this connection, the recent work of Beutel and Kutzelnigg ( 2 ) indicates that the fluorescence of different samples of zinc oxides is governed by the oxides themselves and not by the impurities present.
IXFLUENCE OF STATEOF T'ULCANIZATIOS O N FLUORESCEICE OF RUBBER STOCKS The coinpositions of a number of the compounds used in the study of the fluorescence of rubber itself in various states of vulcanization are shown in Table VI. Most of these stocks were not prepared particularly for this investigation but were those upon which other studies happened to be in progress a t the time. French process zinc oxide (sample 5 of Table IV) was used in these stocks.
INDUSTRIAL AND ENGINEERING CHEMISTRY
110
TABLEVI. COMPOSITIONS OF COMPOUNDS EXAMINED 1 Smoked sheets Sulfur Zinc oxide Captax
D.0.T. G.
100 5.25
.. .. ..
3 100 3 3
2 100 3 3
... 0.6
.. ..
... 0.6
...
Stearic acid 0.5 Calcenea * Whiting treated with fatty acid.
0.5 59.1
4 100 3 126 1
5 100 5 126 2
... ... ... ... ... ...
6 100 3 5.2 0.54
......
Table VI1 lists the values for modulus and tensile strength, together with the data on fluorescence, for samples of these various stocks after vulcanization for dzerent periods of time. The well-vulcanized specimens always exhibited a pronounced yellow fluorescent color, regardless of the quantity of such pigments as zinc oxide or whiting which might be present. The presence of carbon black in the compounds gave them such a dark background that differences in the fluorescent effect could not be observed. Since the fluorescent color could apparently be of value as a criterion for the state of cure only if a marked change in the intensity of fluorescence coincided with some characteristic value for the modulus or tensile strength, the points at which the greatest changes in fluorescence occur are indicated in Table VII. In the case of compound 1 the unvulcanized stock was also exposed to filtered ultra-violet light. While this sample showed a little fluorescence, the resulting color was more of a light brown than the rather bright yellow of the vulcanized samples. Although the more completely vulcanized specimens of compound 1 fluoresced uniformly, such was not the case with some of the other samples-e. g., that cured for 60 minutes. This latter sample showed streaks of highly fluorescent material adjacent to portions which fluoresced but little. This peculiar effect led to an appearance suggesting the possibility that fluorescence is altogether a surface phenomenon. This possibility was further strengthened by the fact that repeated scratching of the surface lessened the intensity of fluorescence but was weakened by the observation that vigorous washing of the surface with water, acetone, ether, gasoline, and benzene produced no effect. Final proof that fluorescence is not purely a surface phenomenon was obtained by comparing the appearance of freshly cut surfaces with that of those which had been in contact with the mold during vulcanization. There was no significant difference between the fluorescent effects obtained in the two cases with well-vulcanized samples.
SAMPLE
TEMP.OF CVRE TIME OF CERE O
The freshly cut surfaces of undervulcanized samples appeared to fluoresce much more uniformly than did the molded surfaces. The states of cure a t which the greatest change in the intensity of fluorescence occurred were markedly different with the various stocks. Only in the case of the rubber-sulfur mix (compound 1) did the greatest change in fluorescence coincide with the approach of optimum tensile strength. The maximum change in fluorescence occurred considerably before the attainment of maximum tensile strength in the case of compound 2, and after it in the case of compound 3 (which differed from compound 2 only in containing 20 volumes of Calcene). Although the greatest change in fluorescence occurred a t a point not far from that of the optimum properties for compound 4,it appeared after the attainment of maximum tensile strength in the case of the similar but more highly accelerated compound 5. In the case of compound 6 the maximum change in fluorescence occurred much past the stage a t which optimum values for modulus and tensile strength were obtained. To what extent these results were influenced by the fact that this stock had undergone natural aging for about one year before being tested and examined is not known.
EFFECT OF LIGHTON FLUORESCENCE OF VULCANIZED RUBBER While obtaining the data shown in Table VII, it was observed that portions of samples which had been exposed to light in the laboratory for some time did not fluoresce as intensely as the portions which had not been exposed. In the f i s t attempt to evaluate this effect, it was found that exposure to light about 20 feet (6.1 meters) from a row of windows in the laboratory for 3 hours produced no apparent effect on the fluorescence of a well-vulcanized specimen, whereas a similar exposure for 2 days (about 32 hours of daylight of varying intensity) led to a small but distinct diminution in the degree of fluorescence. Sections of the sample of compound 1 cured for 180 minutes were then exposed to direct sunlight on the roof for definite time intervals. Five minutes of exposure produced no effect, 15 minutes caused a noticeable decrease in the intensity of fluorescence, 30 minutes a further decrease, and 60 minutes a much further decrease. In fact, after exposure for 60 minutes the intensity of fluorescence was less than was the case with the sample of this stock vulcanized for only 40
AND PHYSICAL PROPERTIES RELATIONS BETWEEN FLUORESCENT EFFECTS
TABLEVII. COMPOUND
c.
Min.
Smsss AT ELONQATION OF:
400%
Kg. per
600% sq.
cm.
1
2 -
3
A B C
138
4
A
127
C D
40 60 80 100 10 20 30 40
B C
20 30 45
D
B
9 16 21 23 70 88 95 97 26 53
61 69
.. .. .. .. .. .. .. ..
.. .. .. ..
5
6*
D
60
... ... ... ... ... ...
77
83 79 72 67 65
TENBILE STRENGTH
Kg. per
I N T B N ~OF I TFLVORESCENCE Y (YELLOW COLOR)
sq. cm.
58 121 190 199 199 99 170 184 207 226 277 267 270 25s 132 234 253 258 260 262 242 207 220 202 197 197 170 176
Little Somewhat more than A Very much more than B" Very slightly more than C' Very slightly more than D Very slightly - more than E Little, if any" Considerable" Slightly more than B Slightly more than C ~
Some5 Considerable' Slightly more than B Slightly more than C Little More than A More than B' More than Ca Little More than A" Much more than B" Slightly more than C Little. if any More than A More than B"more than C0 Considerably
Sliahtly more than D 75 Slightly more than E 90 Successive samples between which the greatest difference in the intensity of fluorescence was found t o exist. -411 the data with respect to compound 6 were obtalned after the samples had been stored in the dark for about one year.
5
6
Vol. 26, No. 1
January, 1934
I ND U S T R I A L A N D
E N G I NE E R I N G C H E M I S T R Y
minutes (Table VII). After being subjected to sunlight for 2 hours, the sample showed practically no fluorescence. After storage in the dark for 10 days, there was apparently no evidence that the exposed sample had recovered its capacity for fluorescing. Examination of freshly cut sections demonstrated that the loss in fluorescing capacity had occurred only in a thin layer of rubber a t the surface exposed. Since exposure of a sample to the unfiltered light from the mercury vapor lamp for 18 minutes resulted in a considerable decrease in the intensity of fluorescence, it seemed that the ultra-violet light in the sun's rays might be the active agent in the effect produced by sunlight. On the other hand, the loss in the intensity of fluorescence appeared to be just as great in the case of a specimen exposed to direct sunlight beneath a layer of window glass 3 mm. thick, as with a similar specimen not covered with glass. The fluorescence of phenyl-/3-naphthylamine and of cuprous cyanide was not affected by exposing them to direct sunlight for one hour.
ACKNOWLEDGMEXT The Writer wishes to Inake acknowhkment of the cooperation of H. P. Coats and J. H. Dillon of this laboratory,
111
and of G. S. Haslam of the New Jersey Zinc Company in the matter of providing the samples of zinc oxide of varying particle size. LITERaTURE CITED
(1) Beutel, E., a n d Kutaelnigg, 8..Monatsh., 55, 158 (1930). (2) Ibid., 61, 69 (1932). (3) Bruni, G., see Cotton, F. H . , Rubber Age (London). 12, 307 (1931). ( 4 ) Ditmar, R., Caoutchouc & gutta-percha, 28, 15,685 (1931). ( 5 ) Ditmar, R., a n d Dietsch, W., Chem.-Ztg., 52, 388 (1928). (6) Haitinger, M., Feigl, F., a n d Simon, .I.,Mikrochemie [ Z ] 4, 117 (1931). (7) Kirchhof, F., Kautschuk, 4, 24 (1928). (8) Kojima, K., a n d Nagai, 1..J. Rubber SOC.Japan, 2, 260 (1930). (9) Krahl, M., Kautschuk, 3, 159 (1927). (10) Mulliken, "Identification of Pure Organic Compounds," Vol. 3, Wiley, 1917. (11) Nagle, P. G., Inst. Rubber Ind. Trans., 3, 304 (1927). a n d Pfund, A. H . , IND.ENQ.CEEM., 19, 6 1 (12) S t u t s , G. F. -I., (1927). RECEIVED September 20, 1933. Presented before the Division of Rubber Chemistry a t the 86th Meeting of the American Chemical Society, Chicago. 111.. September 10 to 15, 1933.
Gas Absorption Apparatus ROBERTT. DILLON,Hospital of t h e Iiockefeller I n s t i t u t e for Medical Research, N e w York, N. I-. EVERAL types of gas absorbers or gas-washing devices are satisfactory for macrowork. Of these, the filterplate and spiral types are probably the most efficient ( 4 , 5 ,8, Q),but the choice is perhaps best left to the individual. For semimicro- and microwork the general use of either filter-plate or spiral type is somewhat restricted because of the large volume of absorbing solution required and glassblowing difficulties. An exceedingly simple absorber adaptable to either macro- or microwork which avoids these two objections and which approaches the spiral type in absorbing efficiency is here described. The essential part of the absorber is shown in Figure 1. The dimensions of the absorber used in this laboratory are as follows: The glass tube A , 5 mm. in. .D side diameter, is constricted to FI-an inside diameter of 0.6 mm. for a distance of 8 cm., A piece of tubing the same size as A is sealed to A at D where the constriction begins. Tube C extends 1 cm. beyond the tip of B . Three small holes, E , 1 mm. in diameter, are placed symmetrically about tube C, below D. A cross section of the construction at M N is indicated for convenience. The d i m e n s i o n s of the absorber may be altered to suit the need. I n particular, the bore of tube Band the space between B and C can be changed t o accommodate the desired rate of gas flow. The length of the tube will depend on the amount of FIGURE1. DIAGRAM OF absorbent required. ABSORBER Flow of gas indicated b .+ For use the bubbler is simFlow of absorbing hqrncfmdb ply immersed in the absorbing cated by ++
S
B.
liquid in any suitable container. The bubbler may be used with a rubber stopper or sealed into the absorption container to make an all-glass apparatus. Sufficient clearance must be left a t the bottom of the tube so that liquid can easily enter. Gas and liquid leaving a t E should be beneath the surface of the absorbent. ils with the ordinary spiral type, satisfactory absorption is assured by continuous contact of the bubbles rising between B and C with the fresh film of absorbent on the glass walls on two sides. The rapid circulation of the absorbent may be easily demonstrated by the addition of charcoal. The particular advantage of the device lies in its simple construction. In addition, it has practically the efficiency of the spiral bubbler and uses only a small amount of absorbent. I n a vertical position it has the disadvantage of the high hydrostatic pressure required to force gas through it in comparison to the usual spiral type, but the pressure may be decreased merely by tilting the absorber. The device as described has been satisfactorily used for acetone determinations on acetonated sugars by the Messinger method ( 7 ) . The products were hydrolyzed with dilute sulfuric acid ( I , $ , 6) and the liberated acetone removed by adration (Z), the acetone being ahsorbed directly in alkaline hypoiodite solution.
LITERATURE CITED (1) Elsner, H., Ber., 61, 2364 (1928). (2) Folin, O., J. B i d . Chem., 3, 177 (1907). (3) Freudenberg, K., D u r r , W., a n d von Hochstetter, J., Ber., 61, 1735 (1928). (4) Friedrichs, F., Chem. Fabrik, 1931, 203. ( 5 ) Halberstadt, S., I N D . EXQ.CHEM.,Anal. Ed., 4, 425 (1932). (6) K u h n , R . , a n d Rotho, H . , Ber., 65, 1285 (1932). (7) Messinger, P., Ibid.,21, 366 (1888). (8) Rhodes, F. H., a n d Rakestraw, D . R . , IND.ENQ.CHEM..Anal. Ed., 3, 143 (1931). (9) Sieverts, A., a n d Halberstadt, S., Chem. Fabrik, 1930, 201.
RECEIVED Nnvember 14, 1933.
