706
'
INDUSTRIAL A N D ENGINEERING CHEMISTRY
nearly alike that their diffraction patterns could not be distinguished when superimposed. Table I1 gives diffraction data for two chicle guttas, both extracted in the manner already described] gutta A precipitated below 60" C. and gutta B precipitated a t about 60" C. For comparison, the typical patterns of gutta-percha and balata are given. The diffraction data for the chicle gutta A agree with those of gutta-percha, while those of the chicle gutta B indicate a predominance of balata, with only a small amount of gutta-percha. The gutta fraction of chicle, therefore] may or may not be considered a mixture, depending upon the interpretation one places upon the x-ray data for gutta-percha and balata. Von Susich (3) believes that gutta-percha exists in two different crystalline forms, the alpha form stable below 60" C. and the beta form above 60" C. On the other hand, it is pointed out in an accompanying paper (4) that gutta-percha may be a mixture of balata and some other substance which also produces a diffraction pattern. The nature of the extracted chicle gutta and its crystal structure depend upon the temperature a t which the gutta precipitates. The relation between gutta-percha and balata has some bearing on the nature of the gutta to be expected in crude and refined chicle. When originally dried, crude chicle is heated above 60" C., and one would expect to find the gutta present in the form of balata or P-gutta-percha. The diffraction data for crude chicle in Table I indicate the presence of the low-temperature form. This is not entirely inconsistent, however,
Vol. 23, No. 6
since the gutta is only a small percentage of the whole chicle, and it is quite possible that the other constituents exert a stabilizing influence to prevent change in the gutta-percha as the temperature is raised. I n the refining process chicle is held molten considerably above 60" C. during filtration, and the lines due to the gutta have almost disappeared from the diffraction pattern for refined chicle. Von Susich has noted that when it is heated gutta-percha goes through an amorphous stage before assuming the high-temperature structure, and it is again quite possible that this chicle gutta is permanently held in this finely divided state by the other constituents present, thus accounting for the absence of the gutta pattern. Stretching Experiments
Stretching does not produce preferred orientation of the crystals in chicle as it does in gutta-percha, rubber, and similar substances, probably because the chicle is more crystalline than these other substances, and because it is non-elastic and a mixture of several substances. Stretching simply causes the minute crystals (bound together by amorphous material) to flow. Literature Cited (1) (2) (3) (4)
Allen's Commercial Organic Analysis, Vol. IV, p. 420 (1925). Dannerth, F.,J. IND.ENG.CHEM.,9, 679 (1917). Hope, H., and von Susich, G., Keutschuk, 6, 234 (1930). Stillwell, C. W.,and Clark, G. L., INIJ ENG.CHEM.23,706 (1931).
Further X-Ray Studies of Gutta-percha and Balata' Charles W. Stillwell and George L. Clark DEPARTMEKT OF CHEMISTRY, UNIVERSITY OF ILLINOIS, URBANA. ILL
New x-ray diffraction data for gutta-percha and Several specimens of guttaHERE has been considbalata are given and considered in the light of von percha and balata have been erable disagreement as Susich's recent conclusion that these substances are examined. Debye-Scherrer to the significance of identical and exist in two crystalline forms. The data patterns] using molybdenum x - r a y diffraction d a t a f o r also support the assumption that gutta-percha is a r a d i a t i o n ] have been obgutta-percha and b a l a t a as mixture of balata and another crystalline constituent, t a i n e d for all of them, and reported by different investian assumption that is in some respects preferable to pinhole patterns, using c o p gators. The main point a t that of von Susich. Although the relation between per r a d i a t i o n ] have been i s s u e has been the fundagutta-percha and balata has been established and there obtained for some of t h e m . mental difference b e t w e e n may be no ultimate difference between them, it is It was s u s p e c t e d t h a t the g u t t a - p e r c h a and balata. pointed out that the majority of specimens examined d i s a g r e e m e n t a m on g the Clark (1) a n d H a u s e r ( 2 ) of material classified commercially as balata produce several investigators m i g h t have obtained different difa diffraction pattern different from that of guttabe due t o the fact that the mafraction patterns for the two percha, a fact of practical significance. terials examined were from when u n s t r e t c h e d , while different sources. The data Hauser has found them to be the same when stretched. Von Susich (3)has recently done presented herewith are for the following samples: Peruvian much to clarify the problem. He reaches the conclusion, as a block balata, Surinam balata (smoked sheet), deresinated result of x-ray diffraction data, that gutta-percha and balata balata (source unknown)] and Macassar gutta-percha. (Von are identical, and that the substance exists in two different Susich (3) showed that it is not necessary to use purified gutta crystalline modifications, the alpha form being stable below hydrocarbon. The same diffraction patterns are obtained about 60" C. and changing to the beta form when heated above for the pure and impure material] indicating that the diffracthis temperature. Of course, this a t once explains Hauser's tion pattern is that of the gutta hydrocarbon.) The diffracresults, since the specimens were doubtless heated above tion patterns for these, together with those obtained by yon 60" C. when stretched and would then show the beta pattern. Susich for a- and P-gutta-percha, are recorded in Table I. Independent data have been obtained in this laboratory Before yon Susich's work appeared] it had been suspected which, in the main, confirm the findings of von Susich and that gutta-percha was a mixture of balata and another also help to explain further some of the discrepancies which crystalline constituent. This conclusion is supported by two have existed and do exist in the x-ray data for these two facts: substances. (1) The balata pattern is to be found almost complete in the
T
Presented before the Division of Rubber 1 Received January 17, 1931. Chemistry at the 81st Meeting of the American Chemical Society, Indianapolis, Ind., March 30 to April 3, 1931.
gutta-percha pattern, the position of the lines corresponding to within the experimental error with one, and possibly two, exceptions. The spacing of balata, which is noticeably different
INDUSTRIAL A N D ENGINEERING CHEMISTRY
June, 1931
on the gutta-percha pattern, is the line 4.734.75 A. which occurs a t 4.564.68 A. on the gutta-percha pattern. The fact that this line varies on the gutta-percha pattern tends to minimize the lack of agreement of this value with line 4,734.75 A. on the balata pattern. The agreement seems to be more than a coincidence and is therefore suggestive of the interpretation which has been made above, but since the lines are not in perfect agreement the evidence is not necessarily conclusive. ( 2 ) Patterns of an intermediate nature were frequeutly obtained, both for natural gutta-percha and in isolating chicle gutta ( 4 ) in which the intensity of the balata lines varied, indicating a variation of the concentration of balata in the whole gum. Table I-Comparison SURINAM d
(A,)
4.07
I
~~
m
3 93 3.33 2.94
s m
2.72
m
s
707
is a mixture of balata. as such. and another crvstalline form. von Susich did not bonsider'the possibility uof a mixture. Based on his own interpretation, it would mean that his socalled a-gutta-percha is really a mixture of @-gutta-perchaand another constituent. It has been definitely shown that gutta-percha and balata give identical diffraction patterns a t room temperature in some cases; that when the patterns a t room temperature differ, the mtta-percha may be heated above 60" c. and will then give the characteristic balata (or P-gutta-percha) pat-
of X-Ray Diffraction Data for Gutta-percha a n d Balata with Data of von Susich for a- a n d @-Gutta-percha PERUVIAN MACASSAR RESIDUEF R O M BLOCK DERESINATE GUTTA-PERCHABENZEXE EXTRACTIONa-GUTTA-PERCHA 6-GUTTA-PERCHA d~( A , ) I d (A,, I d (A,) I d (A,) I d (A.) d 12.2 vw 4.97 vs 4.96 4.73 vs 4.63 4.56 S 4.07 S 3.89 s 3.94 3.93 s 3.92 s 3.92 3.94 3.29 VW 3.35 3.32 3.33 s 2.95 m W 2.94 2.98 2.94 w 2.96 m 2.95 2 77 w 2.78 w 2.78 m 2.73 W 2.72 m 2.74 w 2 38 w 2.39 w 2.38 W
The results of von Susich (3) throw a somewhat different light on the data of the present writers. It is evident that their gutta-percha pattern agrees very well with von Susich's pattern for a-gutta-percha, while the pattern they have always associated with balata is the pattern of his @-gutta-percha. The data are in satisfactory quantitative agreement, with two exceptions. The largest spacing for a-gutta-percha is too large to be found on the Debye-Scherrer diagram and has been obtained from the pinhole diagram; and it is evident that in von Susich's pattern and that of the writers the diffraction ring from which the value was calculated is so diffusg that no great accuracy can be expected. The value 4.56 A. for a-gutta-percha is not very close to the present writers' corresponding value. Von Susich states that &gutta-percha may be converted into a-gutta-percha, the low-temperature form, by dissolving it and reprecipitating below 60" C. The specimens of deresinated balata and Peruvian block balata were dissolved in benzene and the benzene was allowed to evaporate spontaneously. Each residue produced the pattern recorded in columns 9 and 10 of Table I, the typical pattern for guttapercha. We may still explain all the data a t hand by assuming that the gutta-percha is a mixture of balata and another crystalline constituent, provided it is assumed that a t the so-called transition temperature the second crystalline phase is dispersed in the balata and held in the amorphous state so finely divided that it produces no diffraction pattern. It seems very probable that this is exactly what happens to chicle gutta when chicle is refined. This explanation is favored by the fact that the transformation is not easily reversible. Ton Susich finds that the low-temperature condition cannot be set up again by simply cooling the gutta-percha, but it must be dissolved and reprecipitated below 60" C. If a second crystalline phase were dispersed as the temperature was raised, this would not easily coagulate again when the temperature was lowered; but if the gum were dissolved and allowed to recrystallize, one would expect the two crystalline phases to develop and give their characteristic patterns. Regardless of whether we are dealing with two forms of guttapercha or with a mixture of balata and another substance, the important facts of the case have been admirably set forth by von Susich. The significant difference in the present writers' interpretation depends on the suggestive, if not conclusive, evidence that the pattern for balata is to be found in the gutta-percha pattern, indicating that the gutta-percha
d.)
tern; or the balata may be dissolved and reprecipitated below 60' C. to give the characteristic gutta-percha pattern. The fact remains, however, that for two of the three samples examined which are known commercially as balata, as well as for balata samples previously examined by Clark and Hauser, the diffraction pattern differs from that of samples of gutta-percha. Of course, only a limited number of specimens have been examined and it would be well to consider a greater number of so-called balata specimens. If the diffraction patterns differ from that of gutta-percha in a majority of cases this difference would be of practical significance as a means of classification. Obviously, the discovery that one form may be converted into the other a t will does not lessen the difference between the two forms, although it does explain this difference. It simply means that the product which is generally known commercially as balata is a gum, originally identical with gutta-percha, which has a t some time, either when first coagulated or later, been subjected to a temperature above 60" C. and had its crystal structure and other physical properties changed thereby. Literature Cited (1) Clark, G. L., IND. END. CHBM.,18, 1131 (1926). (2) Hauser, E. A . , Kautschuk, 3, 228 (1927). Ibid., 6, 234 (1930). (3) Hopff, H . , and von Susich, G.. (4) Stillwell, C. W., IND.ENG.CHEM.,13, 703 (1931).
Legal Use of Narcotics Those interested in the distribution and legal use of narcotics will want to examine two recent publications of the Bureau of Social Hygiene, Inc., 61 Broadway, New York, N . Y. One of these deals with "The Legal Use of Narcotics in Detroit, Michigan, and Environs," and is based on an exhaustive examination of drugstore records and prescriptions, as well as records of physicians and other dispensing agents and of scientific institutions for the period of one year. The report endeavors to assist in the establishment of a scientific basis for estimating the amount of legal requirements. The report is available a t 25 cents per COPY. The same organization has published a further study on "The Use of Narcotics under the Provisions of Federal Law in Six Communities in the United States of America." This study was carried forward by the same agencies as conducted the report on the Detroit situation and is based on conditions found in Sioux City, Iowa, Montgomery, Ala., Tacoma, Wash., Gary, Ind., Elmira, N. Y., and El Paso, Tex.
