Nature and Constitution of Shellac SHELLAC LOADED
FOR
TRANSPORTATION
v.
DOWN-COUNTRY
Shellac travels first 40 miles on way to Calcuttll in this mllnner; seed-lac received at these "go-downs" is usually transported in bags on backs of oxen, since early Pllrt of journey is through lac forests.
WM.
Effect of Srnall Amounts of Certain Impurities]
HOWLETT GARDNER
Shellac Hesearch Bureau, United States Shellac Importers' Association, The Polytechnic Institute of Brooklyn, Brooklyn, N. Y. HE abnormalities of a peculiar sample sometimes bring to light facts which might otherwise be overlooked in a general analysis. Therefore, three samples of shellac will be described which might not otherwise be considered, because they are of quality \vhich is seldom encountered. Most of the impurities which are found in shellac occur naturally.
T
SOURCES OF IMPURITIES
Shellac is derived from the incrusted secretion of a multitude of insects which belong to the scale family. These insects resemble to some degree the American tree louse. The remains of their bodies can be readily observed under the microscope in the raw incrusted lac, known as stick-lac. Some of these bodies are found as part of the insoluble material in flaked shellac. In examining stick-lac, numerous fine wax-coated breather tubes can be discerned. These are the source of the shellac wax found in the product of commerce. Stick-lac is gathered by breaking off the branches of the host tree as soon as the new brood of insects has left the incrustation. The raw lac is then crushed by hand, yielding a product containing 70 to 80 per cent resin, contaminated with such natural materials as twigs, bark, insect bodies, and water-soluble substances such as small amounts of secreted sugars, albumin, and red lac dye (8). The lac gathered in November and December is known as the Koosrnie crop. It contains less dye than lac from the Bi-sacki crop gathered in April. The Koosmie lac is usually reserved for making the light colored or fine grades of shellac; the Bi-sacki is either shipped as seed-lac or used to manufacture T. N. grades. Stick-lac from Burma and Indo-China is often much darker in color than the Indian variety, since it contains greater amounts of lac dye. The average shellac made from these lacs is too dark for varnish use (4). Little, if any, reaches this country. However, there are varied grades of Burma and Siam stick-lac, as there are grades or varieties of Koosmie and Bi-sacki lac. Undoubtedlv some of these varieties reach , New York in the form of seed-l~c. In the manufacture of shellac (3-6, 11) the broken up stick1 Parts I-IV have appeared in IND. ENG. CHl~M., 21, 226 (1929) and 23, 1402 (193]); Anal. Ed., 1, 205 (1929); 4, 48 (1932).
lac is ground to particles of the size of beetroot seeds, and graded by means of sifting baskets of different sized openings. These granules are then soaked in water, where considerable woody and extraneous matter floats to the top and is skimmed off. The soaked particles are next placed in large roughsurfaced jars and washed with dilute soda solution, being ground at the same time against the side of the jar by the bare feet of the operator. This process removes most of the water-soluble material and some of the remaining woody substances. The liquid is then strained off through calico, and the granules are placed first in the sun and then in the shade to dry. The dried lac is known as seed-lac, and contains 85 to 90 per cent resin. 'Vhen analyzing seed-lac, it is not uncommon to find particles of pure silica among the impurities. To make flaked shellac, the seed-lac is placed in long narrow fabric bags or tubes, and heated before an open-hearth charcoal fire. The melted lac flows through the fabric, aided by the slow, regular twisting which is applied to the bag. The molten lac collects on the outside of the bag and revolves with it, becoming softer, lighter in color, more shiny and viscous in appearance, and finally dropping on a granite slab in front of the furnace. This slab is kept covered with a thin stream of water. A workman may scrape off the lac which collects on the bag with a large iron knife-shaped instrument. 'Vhen sufficient lac has been collected, it is picked up with this knife and stretched on an iron bottle filled with hot water at 60° C. The stretched shellac is then removed, warmed in front of the fire, and drawn into thin sheets of even thickness by being grasped by the toes, hands, and mouth. 'Vhen cool these sheets are readily broken into the flakes of commerce. In this heat-purifying process, much of the dirt remains in the bag along with some of the less fusible resin. Small pieces of charcoal are sometimes found in shellac as evidence of the use of this fire. If single bags are used, some of the less fusible lac and dirt will pass through the fine mesh and contaminate the shellac. Resin is added in those grades where it is permitted to increase the fluidity of the lac, and arsenious sulfide is put in to lighten the color. Of academic interest to the analyst are the two grades of refuse lac obtained from this process. Kiri or Khirie lac is the powdered product of lac removed from the bags during 550
May, 1933
INDUSTRIAL AND
ENGINEERING
CHEMISTRY
heating when an accident such as clogging occurs, which requires the bag to be cut open at some point and its contents removed. Passawa is the lac reclaimed from the soda washings in cleaning the bags. These refuse lacs are usually combined with willo'wings from the workshop and storage rooms, and are sold in India as Dabugala. This product contains 20 to 50 per cent lac and can be employed for such purposes as sealing wax, but its manufacture is not intended for varnish. No one native makes more than a few pounds of shellac a season, for which he receives little or nothing as judged by our standards of living. Essentially, he is a rice grower, and the little he derives from shellac is pin money. Shellac, therefore, ig practically in every case a composite of flakes which have been sorted to some degree and blended at varied points known as way-houses. These blends are shipped WASHING STICK-LAC IN from one port, Calcutta. When one considers the distances, the varied conditions in India, the skill required in the inShellac is usually a blended product. When a genious yet crude Inode of sample is spread out on white paper, several of manufacture, the many sources the constituent 1)arieties can .be readily disof natural contamination and tinguished. I n some cases the presence of possible variations in stick-lac, natural impurities in one or more of these varieit is indeed surprising to find that shellac is generally of such ties may affect in toto the properties of the a uniform nature. cOTn.posite. This paper describes some extreme
cases u here this was shown to be the case. There can be no accurate means of control in its manufacture with the conditions which prevail in India; by establishing a Board of Inspection, the United States Shellac Importers' Association has been able to eliminate certain blends which would otherwise pass the usual standards. 1
METHOD OF SEPARATING A SHELLAC COMPOSITE
551
MANUFACTURE OF SEED-LAC
were segregated into six varieties: A. Purple-brown flakes, containing visible particles of dirt. B. Yellow-brown exceptionally thin flakes, with golden luster, and visible fine dirt. C. Dull purple-brown flakes, having stri a tion s as if drawn cold. A few twisted end pieces were also found. There were only small amounts of visible dirt. D. Very dark brown-black lumps. E. More or less normal orangecolored, heavy flakes, with considerable dirt. F. Light-colored flakes. varying from ligh t yellow throu~h ora n g e to light brown in color. Many pieces are free from dirt.
If a sample from a specific shellac shipment is spread out on a large sheet of white paper in a good light, definite kinds can be distinguished by the ir color and appearance, and the sample can be separated in this way into several characteristicvarieties. With experience, one can become very adept in examining and separating a composite in this manner. Careful examination, with the aid of a microscope if necessary, shows that the fine pieces differ but slightly in quality from those of the coarser flakes, and that the distribution of varieties, if no blocking has occurred~ is the same for different sized pieces. Where an appreciable segregation is required in order to obtain samples of sufficient size for study and analysis, it is practical to screen several pounds of a composite through a 6-mesh sieve and to separate only the larger material. When no blocked material is present, it is possible, after analyzing the different segregated varieties, to calculate values for the composite. It was found that these values give excellent agreement with those obtained from a sample of the whole shellac.
All of the varieties dissolved readily in 95 per cent ethyl alcohol, and the normal rate of solution was observed in preparing 4-pound cuts (4 pounds of shellac per 1 gallon of alcoho!). Samples C and D gave varnishes which were darker than the standard for this grade of shellac. The order of color, starting with the lightest, is given in Table I. The values obtained by the standard methods (1, 9, 10), used for checking specifications of shellac, give only general information concerning the quality of these varieties. As can be seen from Table I, on the basis of these values alone, only variety D can be considered as strictly abnormal. It shows a slight deficiency in wax, a very high content of material insoluble in hot alcohol, and a high ash content, but with samples A and E the difference between the ash and the material insoluble in hot alcohol gives values which are normal for insoluble organic matter; these varieties can be considered as abnormal only with respect to amount of inorganic dirt.
POOR-BLEACHING SHELLAC
MICROSCOPIC EXAMINATION OF INSOLUBLE CONTENT
The first sample investigated was a shellac ",vhich in the plant had shown very poor bleaching qualities and had required excess bleach liquor to produce the normal color in the product. In general, this shellac appeared to be inferior in quality and possibly a faulty product of native manufacture. The importers had adjudged it as below standard. Official analysis showed it to contain 3.6 per cent material insoluble in hot alcohol and 1.4 per cent rosin. However, at the time this shellac was received, the only claim that could be officially made against it was that of a small penalty for the 0.6 per cent excess insoluble material on a U. S. Shellac Importers' Association T. N. grade. In the study of thi s shellac 800 grams of the coarser flakes
By treating unground flakes with hot alcohol in a manner identical to that employed in the official analysis (10), it was possible to obtain specimens of the insoluble matter from each variety for microscopic examination. The study of these specimens showed that no marked differentiation could be obtained by this method. However, the general nature of the insoluble material as revealed by the microscope is of interest. The preRence of red clay, some sand, a considerable amount of enmeshing material, presumably albumin, and occasionally an undissolved wax particle, besides small amounts of cellulosic and woody material, could readily be seen. The apparent predominance of albumin was confirmed by
552
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLE I.
ApPROX. % OF WHOLE SAMPLE
VARIETY
26 17 11 19 14 13
A B C D
E F
5 4
Purple-brown Yellow-brown Dull purple-brown Brown-black Orange Yellow-orange
3
6 2 1
TABLE VARIETY
PooR-BLEACHING SHELLAC
ORDER OF COLOR OF ALCOHOL CUT
COLOR OF FLAKES
ApPROX. % OF WHOLE SAMPLE
COLOR OF FLAKES
12 21 12 11 7 14 16 7
Thin yellow-brown Brown Heavy brown Brown-black Orange Red-orange Purple-red Thin greenish brown
II.
D E
F
G H
TABLE III. ApPROX.
%011'
WHOLE VARIETY SAMPLE
COLOR OF FLAKES
ASH
%
%
%
%
3.62 3.15 2.79 5.05 3.93 1.58
1.25 1.35 1.05 1.33 1.69
4.62 4.63 4.81 4.20 4.67
31 22
A B C
D E
7 31 33 5 24
Thin yellow Yellow Red-orange Thin yellow-brown Thin yellow-brown
150 420 8 10 480
WAX
ORDER OF COLOR OF BLEACHING SOLN. AFTER 30 MIN.
5 4
9
2
o
6 3 1
54 19
POOR-FILTERING SHELLAC TIME TO FILTER
TIME TO EXTRACT
Hours 5
35 450 270 15 20 25 35 300
3 2 5 3
MATERIAL INSOL. IN HOT ALCOHOL
ORGANIC INSOL. MATERIAL
ASH
%
%
%
3.99 2.91 3.50 4.03 3.46 4.05 3.40 3.06
1.27 0.77 1.00 1.13 0.90 1.13 0.94 0.81
2.72 2.14 2.50 2.90 2.56 2.92 2.46 2.25
SHELLAC CONTAINING INSOLUBLE LAC MATERIAL INSOL. IN HOT ALCOHOL
ASH
SHELLAC INSOL. IN HOT ALCOHOL
Hours
%
%
%
%
%
%
%
2
8.44 7.50 3.83 4.13 9.02
0.50 1.55 0.40 0.80 1.18
4.92 3.23 0.00 0.00 4.31
0.50 1.55 0.40 0.80 1.18
3.52 4.27 3.79 4.10 4.71
3.02 2.72 3.39 3.30 3.53
14.62 14.70 3.76 4.01 14.47
TIME TO TIME TO FILTER EXTRACT
Min.
EXCESS BLEACH LIQUOR REQUIRED
ALCOHOL INSOL. MATERIAL
Min.
A B C
Vol. 25, No.5
2
the odor of burning nitrogenous matter detected on ashing the insolubles, and by treating samples with hydrochloric acid, which dissolves the material. This dissolved albumin can then be readily precipitated from solution by careful neutralization with ammonium hydroxide or ammonium carbonate. It was darkly colored with absorbed lac dye, as well as the woody matter. In order to facilitate the examination of the insoluble contents for charcoal, the dark purple-colored constituents insoluble in alcohol were treated with bleaching solution. This removed the albuminous material as well as the color. Some samples showed the presence of small amounts of charcoal, but in no case a sufficient number of particles to account for the poor bleaching properties of this shellac. BLEACHING TEST
Since the above tests showed no outstanding abnormalities in the shellac other than possibly the colors of two of the varieties and the general quality of the small amount of fraction D, it was necessary to carry out some type of approximate bleaching t.Ast in order to determine what part of the shellac imparted the poor bleaching property:
ORPIMENT
INSOL. l\1ATERIAL Resin-free Original
MATERIAL INSOL. IN COLD ALCOHOL
showed normal bleaching properties. The values for percentage of excess bleach are given in Table I. Since none of the above fractions imparted any material coloration to water when they were soaked for 48 hours, it is clear that any lac-dye present in these samples must be intimately fused into the shellac. If lac-dye were present in such a condition, it would not be surprising to find that an excess bleach would be required. On the other hand, the poor bleaching properties of these varieties may be explained by assuming that a chemical reaction has taken place between the dye and the resin, or that a dehydration of the yellow insoluble dye, erythrolaccin, has occurred with the formation of its red anhydrous product (7). Regardless of what theory may be accepted to explain this condition, the facts indicate that the amount of dye I3resent in this state is minute in comparison with the amount of bleaching solution required to decolorize these last traces of color material, and that it is the presence of the small traces of what may be called "fixed" dye in some of the varieties which gives rise to the poor quality of the composite. Further studies ar'e in progress on the bleaching quality of shellac, which will be reported in subsequent papers. POOR-FILTERING SHELLAC
A IO-gram sample of each variety waR dissolved in 100 cc. of soda solution containing 1 gram of sodium carbonate, by heating on a water bath maintained at 65° to 68° C. (about 150° F.) with constant stirring for 1 to 1.5 hours, and then digesting for 0.75 hour with occasional agitation. The soda solution was allowed to coo], and 30 cc. of sodium hypochlorite solution (2 per cent available chlorine, at pH = 10) were added and permitted to stand overnight. By adding 1 to 2 cc. of excess bleach solution every 2 hours until the samples attained the same light yellow-cream color of bleached shellac, it was possible to obtain a quantitative value for the bleaching quality of each variety.
Although this method does not strictly duplicate plant procedure, approximate values for the amount of excess bleach can be obtained by dividing the total amount used for each variety by the amount for variety F, since this sample
This sample was a pure T. N. shellac, which upon official analysis was reported to have required several hours for filtration in the determination of the content insoluble in hot alcohol (10). Rumors were current that imports of gum Dammar Batu (Bastard Dammar) had been received in the Calcutta district of India, and that the addition of this resin might account for the poor laboratory filtration. The results show that such reports of adulteration had no foundation whatever. In accordance with the above described procedure, this sample was divided into the following varieties: A. Yellow-brown, very thin flakes with golden luster and visible particles of dirt; similar to variety B of the previously described sample.
May, 1933
INDUSTRIAL AND
ENGINEERING
B. Brown flakes which are fairly heavy and contain some visible dirt. C. Brown, heavy particles and flakes, some very dark. D. Dark brown-black particles and flakes j simila.r to variety D of the previous sample. E. Dark orange, normal T. N. color with some visible dirt; a few clean particles similar to sample E of the previous investigation. F. Red-orange flakes with visible dirt; similar to E except in color. G. Purple-red-brown, fairly heavy flakes with visible dirt; similar to variety A of previous sample. H. Greenish brown, thin flakes with visible dirt; some pieces were quite clean.
CHEMISTRY
553
safe to say that difficulties experienced with this poor-filtering shellac are not apt to be caused by adulteration with other varnish resins-certainly not with gum Batu. On the other hand, the suspending material was shown to contain 25 per cent of very finely divided inorganic dirt and 75 per cent of organic material containing considerable nitrogen. A large part of the organic insoluble material showed the same characteristics as that of the protein material found in the poor-bleaching shellac. This gelatinous material coated the sides of the thimbles, and, if allowed to air-dry before extraction, cracking of the impervious film took place, which then permitted normal extraction to follow. Use of acidulated alcohol aided the filtration. In other respects the varieties of this shellac were what might be considered normal. The orpiment content of all sampIes was less than 0.1 per cent. Acid numbers were normal and the water extracts free of mineral acid. No evidence was obtained of the presence of insoluble lac.
As might be expected, varieties B, C, and A elogged the thimbles when their hot-alcohol solution was filtered. These thimbles when full of alcohol required 2.5 to 3 hours to empty, even after being subjected to hot alcohol for 2 weeks. In Table II the percentage of insoluble material reported for these samples, however, is based upon the value obtained at the end of SHELLAC CONTAINING 5 hours. It was felt INSOLUBLE LAC that such values Difficulties of represented a more laboratory filtration accurate resul t, alare not confined comthough they differ but pletely to samples slightly from those containing protein SPREADING SEED-LAC FOR DRYING IN SUN obtained after the 2material. The third week treatment. .By Woman in background nearest door is carrying sieves for sorting lac; third figure from right is spreading lac with tray used in willowing and cleaning raw ground lac. sample investigated subtracting the illustrated the diffivalues given in Table II for percentage ash from those for total material insoluble in culties encountered when insoluble lac is present. This sample hot alcohol, it can b,e seen that the organic impurities are had an exceptionally light color for a T. N. grade. It was lower, if anything, in these varieties than in the ones which reported to have caused difficulty in filtration, showing a high content of material insoluble in cold alcohol, and high infiltered readily. By dissolving 20 grams in 400 cc. of hot alcohol and re- solubility when cut in soda solution. The following separamoving the insoluble material by centrifuging, the clarified tions were effected: shellac solutions in all cases filtered freely through the thimA. Thin, light yellow-orange flakes free of visible dirt; these bles. Thus it was clear that the clogging material was con- were slightly more brown than most of the light-colored pieces tained in the insoluble materiaL To investigate the insoluble found in the poor-bleaching shellac, but differed from the shellac content, the material removed by centrifuging was then of the previous sample by the absence of brilliance or high reof light. purified by repeated treatments with hot alcohol and finally flection B. Yellow-orange flakes of normal thickness; texture similar with hot carbon tetrachloride. When the insoluble material to A. was treated with pure alcohol, it had a tendency to form a C. Red-orange flakes, very similar to varieties F and G of the suspension, whereas the residue from the carbon tetrachloride poor-filtering shellac and variety A of the poor-bleaching shellac. Yellow-orange-brown flakes, very similar to variety A of contained only traces of wax and showed no signs of Batu. theD.poor-filtering shellac and variety B of the poor-bleaching Gum Dammar Batu is insoluble in hot alcohol, but com- shellac; contained visible dirt, and had a brilliance equal to pletely soluble in carbon tetrachloride. It is also partially flakes of previous samples. Except for texture, this variety soluble in amyl alcohol and benzene. Extraction of the could easily be confused with variety A of this sample. E. Yellow-brown, heavy particles and flakes, similar in color insoluble material frorn the poor-filtering grades with boiling and texture to varieties A and B of this sample, though someamyl alcohol, benzene, or carbon tetrachloride did not dis- what duller. solve any of the clogging materiaL Further, using amyl Solution in alcohol immediately revealed that varieties alcohol or a 20 to 80 per cent mixture of 95 per cent ethyl alcohol and carbon tetrachloride as solvents for the shellac A, B, and E contained insoluble shellac. The fine yellow in determining the insoluble content did not give solutions insoluble material settling to the bottom of the bottles conwhich filtered any more readily. But, in order to remove taining the 4-pound cuts of these samples indicated the any doubt with regard to adulteration with Batu, ~rhich might presence of considerable orpiment. Insoluble material obresult from holding a theory that the presence of shellac af- tained by centrifuging, as in the study of the previous sample, fected the solubility characteristics of this resin, small showed an absence of any adulterating gum or resin. The amounts of Batu were fused with a good shellac, and the same difficulties of filtration were encountered as in the product obtained was investigated. In this case the shellac previous investigation. Values for material insoluble in cold alcohol, for ash, and was readily separated from the Batu by filtering a hot alcohol solution of the product. The Batu was recovered from the for orpiment were obtained in accordance with the standard insoluble material with carbon tetrachloride. It is therefore methods (9). The results are given in Table III. In order
554
INDUSTRIAL AND
ENGINEERING
to determine the amount of the original insoluble material or the natural impurities, a method had to be devised for dissolving the insoluble lac. This was accomplished in the following manner: Five-gram samples were dissolved in boiling alcoholic 2 per cent sulfuric acid, and this was kept at the boiling temperature for 30 minutes. The samples were then filtered and extracted according to the standard method for determining material insoluble in hot alcohol. The insoluble material obtained in this manner has been termed for designation the "resin-free" insoluble. This· material showed no evidence of foreign gum or protein, but contained fine orpiment which tended to clog the pores of the filter paper. The original insoluble material is obtained by subtracting the orpiment content from the resin-free insoluble. DISCUSSION OF RESULTS
These samples of shellac can be classified as analytical curiosities because of the rarity with which these types are encountered. On the other hand, from a critical examination of the results, certain general conclusions can be drawn. Table I shows that it would be possible to prepare a shellac from the two varieties F and D which are extreme in their characteristics, and still have a composite which would show a normal color on cutting in alcohol, and normality in its insoluble content. However, such an extreme blend as this would be instantly detected if a sample were spread out on paper and the individual parts observed. Such a blend would be valueless to the manufacturer of bleached shellac, for not only would his costs be increased through the use of excess bleach, but he would also question the advisability of using such a shellac for fear of impairing the quality of his product. Although bleached shellac has been reported to have been successfully manufactured abroad from darker grades of lac t in this country there is a continued demand for higher quality in the orange lac employed for bleaching. Table I is of especial interest, since, by taking the different varieties as individuals, it presents data for shellac of every degree of bleaching quality. It would require a great number of years to collect shellac samples showing the same range of properties. It is practically impossible to tell from analysis carried out in this country exactly what has taken place in India in the manufacture of an abnormal shipment. For instance, variety D in the poor-bleaching shellac may indicate that this sample resulted from the use of single and not double bags in the heating process. If this were the case, the dark lumps would represent the tailings and would be expected to show a high content of material insoluble in alcohol such as is found for this variety. This variety might also represent an attempt to reclaim lac from Dabugala, although this appears to be a remote possibility, since the insoluble content is too low for refuse lac. On the other hand, the dark varieties may have resulted from stick-lac obtained during an offseason, when the rains had not removed normal amount of lac dye from the insect excretion during its earlier soft stages, or from incomplete washing in the preparation of the seedlac. The presence of protein materi'al would favor this explanation. The shellac may have been made from old seedlac. Mahdihassan (5) states1 that "darkening of lac on storing is probably due to the action of a.romonia, liberated by the decomposition of insect skins under the influence of fungi and bacteria." There is, however, no known evidence that such changes take place after shellac has been made into the flake. To the bleacher, the poor-filtering shellac sample would be objectionable because of the quality and color of some of the varieties making up this composite. This would probably require extra bleach liquor. The high ash in parts might lead to difficulties in obtaining proper color for the final product, especially in the presence of the considerable protein material
CHEMISTRY
Vol. 25, No.5
in other varieties of the blend. In. soda solution the protein would have a tendency to carry the fine ash into suspension, which might be precipitated with the bleached lac. For electrical use the presence of albumin may have a tendency to decrease its insulating properties, and, if the insulating material is prepared by the varnish process, this shellac would tend to give a varnish of higher dirt content than is usually obtained by modern spirit-varnish manufacturers. Since this investigation was made, it has become customary to designate on the report of analysis the word "abnormal,'t to show that a shellac has poor filtering properties. As a consequence, practically no shellac of this type is now received in this country. In the sample containing insoluble shellac, those varieties containing insoluble resin also contain unusually large amounts of orpiment. Since the original insoluble material corresponds roughly to a T. N. grade, it would appear that in its manufacture a poor attempt has been made to raise the color of this shellac by the addition of orpiment. Through careless heating or a low degree of plastic flow in the original seed-lac, the excessive heat employed has caused the formation of insoluble lac. EFFORTS TO IMPROVE SHELLAC
Experienced handlers of shellac become skilled in determining the general quality of a shipment without time-consuming and costly analysis. Nearly two years ago the United States Shellac Importers' Association organized a Board of Standards to examine samples of shipments of shellac and seed-lac (2). By obtaining a rejection clause in the importers' contracts, this board has been able to prevent shipments of shellac containing undesirable varieties which might otherwise have passed the usual standards of analysis. Excessive use of orpiment such as was found in the last sample is detected both by examination of the dry flakes and by the confirmatory cuttings in alcohol which are made. Samples of segregated varieties of undesirable lac have been sent to India to demonstrate the types to which this country objects. A standing committee of chemists is continually studying and improving. methods of analysis. Changes have to be brought about slowly, but standardization and improvement in the quality of shellac continues to take place steadily even though the country of its source is shrouded in antiquity and romance. ACKNOWLEDGMENT
The author wishes to express his gratitude to P. N. Rowe for the photographs used in this article, which were taken at the Wyndemgung factory in the Palaman District of India. LITERATURE CITED
(1) Am.. Soc. Testing Materials, Tentative Standards, p. 225,. D29-29T, 1930. (2) Anonymous, Oil, Paint Drug Reptr., 119, No.9, 84 (1931); 121 t No.9, 29 (1932). (3) Clarke, J., Chem. Markets, 26,476 (1930). (4) Mahdihassan, S., Dept. of Indus. and Commerce, H. E. H. the Nizani's Govt., Bull. 2, Govt. Central Press, Hyderabad Deccan, 1925.. (5) Mahdihassan, S., HM. Pidance's Report on Lac Refining," Osmania Univ. Press, Hyderabad Deccan, 1930. (6) Pidance, M. P., Econom. l'Indo-Chine, 108 (May, 1914). (7) Tschirch, A., and LudYt F., Jr., HelfJ. Chim. Acta, 6, 994 (1923). (8) Tschirch, A., and Schafer, H. H., Chem. Umschau FeUe, Ole Wachs6 Harze, 32, 309 (1925). (9) U. S. Shellac Importers' Assoc., and Am. Bleached Shellac Mfg. Assoc., Official Methods of Analysis, 1929. (10) Ibid., Supplement, 1930. (11) Zinsser. W. H., Chern. Markets, 25,596 (1929). t
RECEIVED November 25, 1932. Contribution 5 of Shellac Research Bureau t United States Shellac Importers' Association
