By F. P. VEITCH, CHIEF OF THE LEATHER AND PAPER LABORATORY. INCLUDING NOTES ON THE MICROSCOPICAL EXAMINATION OF SICILIAN SUMAC AND ITS ADULTERANTS,By B. J. HOWARD, CHIEF OF THE MICROCHEMICAL LABORATORY. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1908.LETTER OF TRANSMITTAL. United States Department of Agriculture, Bureau of Chemistry, Washington, D. C, June S, 1908.Sir:I have the honor to submit for your approval a report of two investigations, conducted in 1905 and 1907, concerning the quality of Sicilian sumac imported into this country, chemical and micro-scopical examination of a large number of samples having been made. This study was made in the Leather and Paper Laboratory of the Bureau of Chemistry because of its direct bearing on the leather trade interests of the country, as well as because of its rela- tion to the increased production of sumac in the United States. Material assistance in the performance of the laboratory work involved in this investigation was rendered by H. H. Hurt and C. C.Smoot, of the Leather and Paper Laboratory. I recommend the publication of this report as Bulletin 117 of the Bureau of Chemistry Kespectfully, H.W.TViley, Chief of Bureau. Hon. James Wilson, Secretary of Agriculture CONTENTS Page. Quantity and value of imported sumac 5 Culture and preparation for market 6 Nature of adulteration 7 Investigation of 1905 8 Securing samples for analysis 8 Methods of examination 8 Discussion of results of analysis 10 Investigation of 1907 20 Discussion of analytical data .• 20 Comments by importers 21 Detection of adulteration * 26 Notes on the microscopical examination of Sicilian sumac and its adulter- ants 26 Apparatus and reagents 26 Technique 27 Some histological features 28 – Sicilian sumac (Rhus coriaria) 28 Lentiscus (Pistacia lentiscus) 29 – Tamarisk ( Tamarix africana) 30 Smooth sumac (Rhus glabra) 30 – Chemical determination of adulterants 30 Extent of adulteration 32 – ILLUSTRATIONS. Page. Plate I. Fig. 1.— Sicilian sumac (Rhus coriaria) , upper surface. Sicilian sumac (Rhus coriaria) , lower surface 28 showing papillae of epider- mis. Fig. 2. — Smooth sumac (Rhus glabra), upper surface 30 COMMERCIAL SICILIAN SUMAC QUANTITY AND VALUE OF IMPORTED SUMAC. Sicilian sumac is the best vegetable tanning material known for pale colors and soft tannage, and is consequently extensively used for moroccos, roans, skivers, etc., and for brightening the color of leather tanned with dark materials. An extended investigation a by a committee of the Society of Arts has shown conclusively that sumac-tanned leathers are less likely to be attacked by light and gas fumes, and hence better suited for use in bookbinding than any other known vegetable tannage. As good “masculino,” or Sicilian mountain sumac, contains from 25 to 35 per cent of tannin which is absorbed by hides, it is a very high grade and desirable tanning material, commanding a high price. Consequently it is adulterated to a considerable extent, and much complaint has arisen during the past three or four years both from importers and tanners about the mixing of sumac leaves with stems or other lower-grade and darker-colored substances, an adulteration which not only affects the material, itself, but also darkens greatly the leather tanned. In view of these facts it has been deemed advisable to make a careful examination of imported Sicilian sumac. Although mineral tanning has largely replaced vegetable tanning in the production of morocco, the importations of foreign sumac have remained about the same for a number of years, as shown by Table I, prepared from statistics issued by the Department of Commerce and Labor. Table I. — Quantity and value of sumac imported into the United States from 1870 to 1907 . Year 1905 « Journal of the Society of Arts,London,1901,p. 14.(5) COMMERCIAL SICILIAN SUMAC. CULTURE AND PREPARATION FOR MARKET. Sicilian sumac {Rhus coriaria) is a shrubby bush which grows chiefly in Sicily and Tuscany, and succeeds on any well-drained soil, though the best development is secured in calcareous soils. That grown in the mountainous districts around Palermo is known as “masculino” and contains the highest percentage of tannin — from 25 to 35 per cent — while that grown on the plains is called ”feminella” and usually contains less than 25 per cent. Andraescha states that “feminella” is a variety distinct from “masculino,” stronger, having larger leaves, and containing a darker tannin but less of it than the “masculino.” Examinations of both kinds of leaf have failed to show any differences, and communication with importers brings out the fact that no distinction is made except on a basis of the tannin content. While in this country no attention is devoted to the cultivation of the native sumac, in Sicily it is commonly cultivated, as the yield and value of the leaf are both much greater than from the wild plant. Sumac may be grown on poor, stony, volcanic, or calcareous soils, not too far from the sea, and on mountain sides well exposed to the sun. Sudden changes of temperature or frequent rains, especially when the material is about ready to harvest, greatly injure its quality and strength. The plant may be propagated from the young shoots which form each year about the mature plant, from cuttings of the well-ripened stem, or from the seed. The first method is the one generally fol-lowed. The shoots should be at least a foot high, be well supplied with buds, come from young, healthy plants, and have short chain roots well supplied with rootlets. When cuttings from the wood are made, they must be first rooted in a propagation frame at a tempera- ture of about 70° F. The young plants are set in well-cultivated land in rows 2 feet apart, and are given three or four cultivations during the growing season to keep the land free from weeds and grass.The first crop is harvested the year after planting, either by pruning or by picking the leaves. Harvesting begins about the middle of July, the time being governed by the development of the leaf, the object being to harvest when the leaf has acquired the deepest green color and reached its maximum weight. If the leaves are gathered by hand, harvesting begins when the first and lowest leaves have reached maturity, usually in May, and two subsequent gatherings are made as the younger leaves become fully developed, once late in July or early in August, and again in September, when the extremities of the branches are gathered. After being picked, the shoots and leaves «Abs., J. Soc. Chem. Ind.,1898.NATURE OF ADULTERATION. 7 are allowed to lie in the field in order that they may become partially cured, or they are immediately taken to the barn for curing. It is important that the material be not exposed to rains or to intense sun-shine during curing, as the quality of the product is greatly injured thereby. As a rule, therefore, the best product may be obtained by drying under cover, being careful to turn the leaves frequently to prevent molding. After drying, the leaves and stems are roughly ground, baled, and sold as “leaf sumac,” or they are reground in edge runner mills, sifted to remove the stems, ventilated, bagged, and sold as “ground sumac.” It can readily be seen that the dryness of the product and the proportion of stems that remains with the leaf of the baled and ground sumac will vary considerably according to the care with which it is handled. As these stems not only contain less tannin, but also have a deeper color than the leaf, the value of the product may be materially influenced simply by the method of preparation for market.NATURE OF ADULTERATION.In addition to the incorporation of large quantities of the stem with the leaf, a practice which must be regarded as an adulteration, a number of other materials less valuable for tanning than sumac are mixed with the leaf. By far the most common adulterant, indeed the one almost exclusively used in the sumacs imported into this country, is the leaf of Pistacia lentiscus commonly called lentiscus or lentisco. This leaf contains from 12 to 20 per cent of a catechol tannin, and leather tanned with sumac adulterated with this leaf darkens and reddens on exposure to air, for which reason its use is decidedly objectionable in the manufacture of certain grades of leather. The lentiscus is mixed with ground sumac at the rate of from 20 to 50 per cent, and with the sumac leaves at the rate of 20 to 30 per cent. Other leaves much less generally used in adul- terating sumac are those of Coriaria myrtifolia (“stinco”), Tamarix africana (“brusca”), Ailanthus gladulosa, Vitis vinifera (grape vine), and some species of the Rhus family other than coriaria, as well as foreign material. Sumac from which tannin has been extracted or which has been injured by exposure is also mixed with the normal product. None of these adulterants can be detected by a casual examination of the sumac, but special methods, which will be described later, have been devised for this purpose. The Italian laws require that all adulterated sumac offered for export shall be distinctly labeled with the kind and quantity of the adulterant, but it is claimed that this law is frequently evaded, and the trade journals state that a very large percentage of adulterated sumac has been shipped to this country. Some have tried to justify 8 COMMERCIAL SICILIAN SUMAC. this by asserting that the market here demands sumac at such a price that the genuine “masculine-” sumac can not be sold. How- ever this may be, it appears important that the actual conditions as to purity of imported sumac should be brought fully to the attention of the American importers and buyers, that they may take such steps as appear advisable for their protection. INVESTIGATION OF 1905. SECURING SAMPLES FOR ANALYSIS. Through the cooperation of the customs division of the Treasury Department, the samples for examination were secured at the chief ports of entry in accordance with the instructions in the following letter : January 17, 1905.The Secretary of the Treasury.Sir: In connection with the work of the Bureau of Chemistry of this Department it is desired to obtain samples of sumac leaves and ground sumac entering the ports of New York, Boston, and Baltimore. If in harmony with the regulations of your officeI should be glad if you would issue such instructions to the collectors of the ports named as will enable us to secure the material mentioned. In taking the samples, the names and addresses of the consignor and of the con- signee, together with a copy of all the marks on the bags, should be secured and these data forwarded with the proper samples. Samples should be drawn from about 5 per cent of each invoice by passing a slotted sampling tube from top to bottom of the bags, thoroughly mixing the subsamples of each invoice thus obtained and taking from 1 to 2 pounds of this to be forwarded to this Department with the data above mentioned. In compliance with this request samples of leaf and ground sumac were taken by the Treasury Department, chiefly through the ports of New York and Boston, and delivered to the Bureau of Chemistry. METHODS OF EXAMINATION. The samples were submitted to both chemical and microscopic analysis in order to determine their composition and distinguish the adulterants if such were present. An extractor especially adapted to this purpose was used, numerous experiments a having shown that with this apparatus the extraction of sumac is more complete and the operation is more easily conducted than with other extractors-Furthermore, the color of the resulting extract is less affected than when the ordinary copper Soxhlet, such as is quite commonly employed in tannery work, is used. Inasmuch as the extraction is more complete with this form of extractor than with those formerly used, the results on tannin are, «J. Amer. Chem. Soc, 1905, 27; 724; 1906, 2S; 505.INVESTIGATION OF 1905. as a rule, higher than those obtained and published a few years ago,when rarely more than 25 per cent of tannin was determined in even the best Sicilian sumac. The high results here reported, which are now obtained quite generally by others, are probably due, therefore, to more complete extraction and improved methods of analysis rather than to improvement in the quality of sumac. It has been the opinion among tannery chemists, based on the work of Semour-Jones, Palmer, Parker, and Proctor, of England, that most tanning materials are best extracted at temperatures below boiling; thus sumac is supposed to yield the highest results by extracting below 60° C. The work done in the Bureau of Chemistry makes this opinion no longer tenable, as the highest results have been obtained at from 60° to 90° C. according to the following method, which is now used in this laboratory in extracting all kinds of tannery materials. Place in the extractor, preparatory to receiving the sample, a per-forated porcelain disk and cover with a mat of asbestos or of purified cotton. Place the weighed sample of tanning material in a beaker and moisten with hot water at from 60° to 90° C. until it has the consistency of a thin paste; then transfer it to the extractor, remov- ing all the material from the beaker with a jet of hot water. Let the water percolate through the extractor into a Jena boiling flask, press the material down well, cover with a perforated porcelain plate, and return the percolate to the extractor until it runs clear. Allow a total volume of from 300 to 400 cc to percolate at a temperature of from 60° to 90° C. Place about 250 cc of fresh water in a clean receiving flask and connect it with the extractor by means of a block-tin condenser, heat to boiling, and finish the extraction at steam heat, replacing the extract with fresh portions of water two or three times and being careful to keep the total volume of extract within a liter.When the extraction is completed, usually in from twenty to twenty- five hours, combine the hot extracts in a liter flask and make up to volume when cold. Only the best nonsoluble glass and block tin must be used in the extraction apparatus, as the alkali dissolved from ordinary glass materially dissolves “reds” insoluble in cold water. Make the determination of tannin and other constituents of the extracts according to the official methods of the Association of Official Agricultural Chemists. Determine the moisture by drying 5 grams of substance in a flat- bottomed dish for five hours and check the weight again after drying for three hours. Determine the crude ash in the residue from the moisture by incin-eration at a low red heat until all carbon is burned away, then cool and weigh the residue. S. Dept. Agr., Bureau of Chemistry, Bui. 107, p.35.10 COMMERCIAL SICILIAN SUMAC. To determine the sand, treat the ash with about 10 per cent hydro- chloric acid and warm gently for several hours, filter, wash thor- oughly, ignite, and weigh. The weight so obtained is considered as sand. Make the color determination of the extract with the Lovibond tint-ometer, the readings being made in the 1-inch cell on the soluble solids filtrate, and calculate the results to a basis of 0.5 per cent of tannin in the solution. Give the results in terms of red and yellow, the black being subtracted for the red and yellow readings. It should be borne in mind that the color determination so obtained does not necessarily represent the color of the extract obtained in tannery practice. Indeed, it is almost certain that the color of the extracts as thus prepared for analysis is considerably deeper than that of the extract obtained from the same materials by ordinary tan- nery methods. These results, then, only show the relative colors produced by different samples under like” conditions of extraction and should be compared only among themselves. DISCUSSION OF RESULTS OF ANALYSIS. In tabulating the data on these samples, the name and address of the consignor, when these appeared on the containers, the name and address of the consignee, the approximate date of entry, and the place of sampling are given in connection with the chemical analysis and the microscopic examination. Care was taken to secure sam- ples only from invoices imported in good condition. As is shown in Table II (p. 12), the average percentage of tannin in all the samples of sumac is 28.8 per cent, which is higher than the results generally given in the literature for Sicilian sumac. As has been said, it is not believed that this is due to any improvement in the character of the leaf now grown, but rather to improved methods of extraction and also to changes in methods of analysis. Approximately 41 per cent of the invoices from which samples were taken were mixed with lentiscus, this being practically the only adulterant employed, except sumac stems, which were present in excessive quantities in a number of samples. The adulterated sam- ples contained from 19.6 per cent to 33.3 per cent and averaged 26.6 per cent of tannin, or 2.2 per cent less than the average of all the sumac samples. A number of the samples contained an excess of sumac stems, and the average tannin content of these was 29.9 per cent, which indicates that the stems are not added in such large quantities as is the lentiscus. The samples of pure sumac contained from 27.4 to 35.1 per cent and averaged 31.9 per cent of tannin. Adulteration of the average pure sumac with 30 per cent of the average lentiscus would yield an article having the same percentage INVESTIGATION OF 1905. 11 of tannin as the average adulterated samples — that is, approximately 27 per cent. The figures, therefore, indicate an average adulteration of 30 per cent of lentiscus, which is possibly below the actual practice, as high-grade sumacs are more likely to be adulterated than the lower grades. Several of the samples, however, contain so little tannin that it is evident that either an exceptionally low grade of sumac was used or that lentiscus was almost entirely substituted. Ten samples were marked as containing lentiscus. In two cases the examination proved the sample to be pure sumac. In no case was more than a 25 per cent adulteration admitted. The average tannin content of the six admittedly adulterated samples is 27.5 per cent, practically identical with the average of all the adulterated samples. If the general statement that the “feminella” sumac contains less than 25 per cent of tannin is accepted, it would appear that none of the adulterated samples was plain-grown sumac. As this classifica- tion seems to be based solely on the tannin content, it may be ignored except in so far as it is an expression of the agricultural fact that sumac grown on the high ground contains more tannin than that grown in the valleys. Leather tanned with sumacs adulterated with lentiscus is darker than that tanned with pure Sicilian sumac, and the determination of the color of the extracts from these samples is in harmony with this fact. The darkest extract from a pure sumac contains less red color- ing matter than the lightest-colored extract from an adulterated sample, while the extracts from the samples of lentiscus contained several times as much coloring matter as the darkest pure sumac extract. COMMERCIAL SICILIAN SUMAC. DETECTION OF ADULTERATION.NOTES ON THE MICROSCOPICAL EXAMINATION OF SICILIAN SUMAC AND ITS ADULTERANTS. By JB. J. Howard, Chief,Microchemical Laboratory.The differentiation of pure and adulterated sumac by means of the microscope is not at all a new procedure, but it does not appear to be generally employed by the trade in this country. The work done in this laboratory indicates that this is a convenient and quick method of identifying certain of the common adulterants in Italian
sumac leaves, and that in the detection of, the most common adulter- ant, Pistacia lentiscus, no great experience is necessary to obtain reliable results. The examinations here reported include only com-mercial samples, most of which were in a powdered form, and hence no studies of sections were made. The investigations have been in progress since 1903. The paper by Priestman” will be found very useful to beginners along this line, but the technique of the method as there described seems to leave something to be desired in the way of simplification. As will be shown, the technique adopted in this laboratory is quite different, and, it is believed, has some advantages over Priest man’s. APPARATUS AND REAGENTS.The most important apparatus required is a good compound micro-scope giving a range of magnification of from about 75 to 200 diame-ters. Magnifications of 90 and 180 were actually used in the work here reported, but if approximately these powers are used, giving good definition, no trouble should be experienced. The instrument should have fine and coarse adjustments and a substage condenser with iris diaphragm. A mechanical stage with wide range of move-ment (about 2.5 cm or more) will be found very convenient, though it is not really necessary. Microscope slides 25 by 75 mm (1 by 3 inches) and cover-glasses, round or square, are required, round covers of 0.75 inch diameter and from 0.17 to 0.25 mm in thickness, listed by some dealers in micro-scopical apparatus as No 2, are preferred. Some device for produc-ing a small flame, such as a micro-bunsen burner or small alcohol a J. Soc. Chem. Ind., 1905,DETECTION OF ADULTERATION. lamp, is required. In addition to the above, a pair of teasing-needles,a pair of small forceps, and a scalpel should be secured. As a clearing agent a chloral hydrate solution made up as follows was almost exclusively used: Chloral hydrate, 150 grams; water,100 cc. Among other reagents of occasional value the following should be noted: Alcohol of two strengths, 70 per cent and 95 per cent; two grades of glycerin, 100 per cent and 50 per cent (glycerin and water 1:1 by volume), and glycerin jelly are needed if permanent speci-mens are to be made, and this will almost always be done by careful workers. The glycerin jelly is made up as follows: Best gelatin, 1.5 parts; water, 3 parts, and glycerin, 4 parts. Some persons a prefer to use only 1 part of gelatin, since it gives a jelly more easily worked than the amount mentioned. Soak the gelatin in the water until it is soft, add the glycerin, and heat over a water bath, finally adding two or three drops of carbolic acid as a preservative.TECHNIQUE. The difficulty encountered on examining specimens mounted in water or glycerin direct is due to the fact that they are too opaque and contain considerable air. Some means of clearing the frag-ments are necessary.Priestman6 treated the sample with nitric acid, which attacked the more delicate tissues of the leaf first, and if the action was stopped at the right time,the leaf epidermis could be mounted as nearly clean tissues. This method is laborious if a large number of samples is to be tested, and seems to require con-siderable judgment as to just the stage at which the action is to be stopped, and hence is not desirable unless one is very familiar with microscopical technique. In this work the chloral hydrate solution before mentioned was used. A small amount of the specimen is placed upon a slide with two or three drops of the solution and gently heated to boiling over the micro-bunsen burner or alcohol flame and kept gently boiling for about one minute. If the chloral hydrate solution boils awa}^ before the heating is finished, a few drops more are added, for if the specimens become dry the object of the treatment is defeated. After the boiling is completed the specimen is allowed to cool down some-what, a cover-glass is placed over it and the specimen is ready for examination. If too much of the original specimen has been used, the mass will be too dense to give satisfactory results. A few tests, however, will demonstrate to the worker the most satisfactory amount a Clark’s Practical Methods in Microscopy, 2d edition, 1896, p. 243.COMMERCIAL SICILIAN SUMAC. to use. It is well to make several slides from the specimen, so as to get a good idea of its character. Another method of procedure which some may prefer, and which lends itself readily to the examination of finely powdered samples, is the following: Place in a test tube a portion of the sample equal in size to a hazelnut, add a few cubic centimeters of the chloral hydrate solution and boil slowly for two or three minutes, allow to stand until the larger pieces have settled to the bottom and then remove a part of them with a pipette and mount on a slide in the usual manner. Such treatment is all that is necessary in the preparation of samples for immediate examination. It is often desirable, however, to pre-pare specimens for future reference. For this purpose the specimen is cleared with chloral hydrate as described, the excess liquid is removed by a piece of filter paper, and then mounted in glycerin or glycerin jelly. To mount in glycerin, add to the moist fragments a small drop of the 50 per cent glycerin and -after covering seal with a good microscopical cement. In order to mount in glycerin jelly, the sample is cleared and the excess chloral hydrate solution removed as previously directed, a tiny drop of 50 per cent glycerin is mixed with the moist fragments, and then a small piece of glycerin jelly (about a quarter of the size of a pea) is placed on the slide. The whole is gently heated until the jelly melts, and the fragments are mixed with the jelly by means of a teasing-needle or scalpel, care being exercised not to make bubbles in the mass, as they are difficult to remove. Care should also be taken not to heat the glycerin jelly on the slide enough to produce bubbles. Permanent samples can be made, after clearing in chloral hydrate, by dehydrating in alcohol, clearing in xylol, and mounting in xylol Canada balsam. This method is not satisfactory, however, unless the sample is stained; and with many small fragments, as is usual in a powdered sumac, this step is somewhat difficult and tedious. SOME HISTOLOGICAL FEATURES. A short description of the most characteristic histological features of sumac and the most important of its adulterants may be of value. Although written descriptions and photographs aid greatly, in begin- ning such investigations the microscopist should, of course, first work on samples of known purity, then on known mixtures, and finally on mixtures of a content unknown to him but prepared from authen- tic samples.Sicilian Sumac (Rhus coriaria). The upper epidermis of Rhus coriaria (PI. I, fig.l) is made up of cells about 35yw in diameter (varying from 20 ju to 50yw). They appear in the surface view to be bounded by walls with fairly straight sides — Bureau of Chemistry, U. 5. Dept. of Agriculture. DETECTION OF ADULTERATION. that is, the individual segments of the periphery are but little dis- torted or curved. The walls are thin and have a slight beading due to deep, broad, regular pits, while the corners come down to quite sharp definite angles. There are present an abundance of horn- shaped hairs (trichomes) from 50/* to 400/* long and from 35/* to 70/* diameter at the base. Although the cavity in some of the hairs, especially the smaller ones, is simple, in many of them it is divided by transverse septa into two or three chambers. The epidermal cells adjoining each trichome are commonly from 8 to 14 in number, though these limits are at times exceeded. They are much smaller in average size than those of the intra-trichome regions. The cells of the under epidermis (PL I, fig. 2) are somewhat smaller than those of the upper epidermis, and the walls are much more bent or curved, giving the cells very irregular outlines. The beading of the walls is of about the same prominence as in the upper surface. On the under surface are two kinds of trichomes: (1) horn-like forms similar to those on the upper surface but usually longer; (2) glandular forms of from 3 to 4 cells, raised on a single-celled stalk, the whole forming a club-shaped structure. The horn-like trichomes of both the upper and lower sides of a leaf have commonly a slightly warty surface. The lower epidermis is also furnished with many stomata or breathing pores, but there is no such regularity in the number and arrangement of the adjacent epidermal cells as in the case of the lentiscus. Rosette crystals of calcium oxalate are often visible in the leaf tissue when viewed from either side, though some leaves show but few or none. An excess of stems is detected by the presence of fibrous tissue in greater amount than in good normal samples. Many fragments of the powdered sumac leaf will show only the trichome scars, since in grinding they are frequently broken off. Lentiscus (Pistacia lentiscus). The method of clearing by chloral hydrate has a tendency to pro-duce clearer tissue in P. lentiscus than with R. coriaria. Both sur-faces of P. lentiscus are free from trichomes. The upper epidermis (PL II, fig. 1) is made up of cells having very conspicuous walls. The outlines of the walls are straight and at the angles, instead of coming down to sharp points, are slightly rounded, giving to them a very distinctive appearance and one not to be confused with the surface appearance of R. coriaria or any of its other common adul-terants. This point is not so clearly shown in the photomicro- graph as in the specimens themselves since this feature was subor-dinated to producing the best general effect, the latter being much more important in its identification. The cells vary in width from 17/* to 30/*. COMMERCIAL SICILIAN SUMAC. The under epidermis cells (PL II, fig. 2) have not quite so promi-nent walls as those of the upper layer and the outline is more inclined to be wavy. The limits of variation in diameter also exceed those of the upper surface. From six to ten cells are radially grouped around each stoma. In the ordinary-clearing process these cells,together with the stomata, commonly clear up more perfectly than the rest of the epidermal cells, thus giving to the specimen when viewed under the microscope with the objective slightty out of per- fect focus a mottled appearance which is very characteristic. Tamarisk (Tamarix africana). This material cleared in chloral hydrate is more brownish in color than the species previously mentioned. The most characteristic feature observed is a papillae-like appearance on the surface of the leaves distinguishing it from the other plants studied. This is best observed on fragments which lie partiallyon edge, in which position the little protuberances are readily seen. Smooth Sumac (Rhus glabra). Though this species is not very commonly found if at all in Rhus coriaria as imported into this country, it is one of the possible adul- terants that should be kept in mind. On neither surface of the leaf are the horn-like trichomes present. The cells on the upper epider- mis resemble those on the upper epidermis of the R. coriaria, being ordinarily from 25pt to 52/i across. The beaded cell walls noted in the case of the R. coriaria are very pronounced in the R. glabra, and, together with the absence of trichomes, have been used as the basis of its identification. The under surface of the leaf has epidermal cells and stomata and glandular hairs very much like the R. coriaria, but the cell walls do not generally show quite so much undulation. The fact that the horn-like trichomes are absent from both sides of the leaf is of addi- tional service in the identification of whole or rather coarsely ground material, but in very finely ground samples can not be relied upon with certainty. CHEMICAL DETERMINATION OF ADULTERANTS.In the detection of adulterants it is customary to place depend- ence only on the microscopical examination of the sample, no chemi- cal tests being regarded as of practical value for this purpose, although Proctor a states that any sumac infusion rendered turbid by bromin water is open to grave suspicions. Work in this laboratory has shown that while pure sumacs are not as easily precipitated, requir- ing more bromin water than lentiscus extracts do, both the sumac a Principles of Leather Manufacture, 1903.Bureau of Chemistry, U. S. Dept. of Agriculture. Bureau of Chemistry, U. S. Dept of Agriculti. DETECTION OF ADULTERATION and its adulterants give a precipitate on treating with a quantity of saturated bromin water, and, as a consequence, but little reliance can be placed on this test. One of the most reliable indications of adulteration is the color of the dried sample. If lentiscus is present it will darken greatly on heating, becoming a dirty light brown with a tinge of red, while pure sumac only turns a slightly darker yellow. The experienced analyst, having a pure sumac for comparison, can pick out in nearly all cases samples adulterated with lentiscus. That this test agrees well with the microscopical examination is shown by the last column of Table II, where the purity of the samples as indi- cated by the color after drying is given. Of a total of 91 samples examined, 82 agreed with the microscopical test, 3 were doubtful, and 5 were erroneous. Moreover the color of the extract has been found a valuable indication, samples adulterated with lentiscus giv- ing a dark reddish extract, easily distinguished from pure sumac. As a rule, therefore, the experienced analyst can distinguish by means of the color of the extract and the dried material those sam- ples which are adulterated with lentiscus, but if there is any uncer- tainty a microscopical examination must be made. Neither the percentage of ash nor of sand is an indication of adul- teration with lentiscus, as this leaf does not differ materially from sumac in these particulars. The samples of leaf and ground sumac contained on an average 1.41 per cent of sand, the highest amount found being 3.05 per cent. Assuming that there was no sifting out of sand in transit, there was no evidence of willful addition of sand to these samples, although several indicated that they were but imperfectly winnowed or ventilated. There was less than 1 per cent of sand in the unground leaf, while 106 samples of ground leaf aver-aged 1.62 per cent and 15 contained more than 2 per cent. Therefore 2 per cent of sand may very properly be considered the maximum sand content of a well-ventilated ground sumac. A larger content of sand indicates that the samples have been carelessly prepared. EXTENT OF ADULTERATION. From 25 to 41 per cent of the invoices of Sicilian sumac imported into the country are adulterated, and this adulteration is effected almost exclusively with lentiscus. These adulterated shipments are, as a rule, so labeled as to convey the impression that they are pure Sicilian sumac. It is sometimes claimed that shipments of sumac are mixed with lentiscus in accordance with the order of the importer. In such cases the consignment should be properly labeled indicating the amount of lentiscus used.The tannin content is from 2 to 7 per cent lower in the adulterated samples than in the pure sumacs, averag- ing about 4.5 per cent lower, and the color of the extract prepared from them is much darker than that of pure sumac extracts. While to the experienced analyst the color of the extract or of the dried material is generally indicative of the purity of the sample, only microscopical examination can definitely determine this question. The adulteration of Sicilian sumac is of more importance than is indicated merely by a lower tannin content, otherwise American sumac could be used at a much smaller cost. When high-grade, light-colored leathers or durable sumac-tanned leathers are required, as for instance in bookbinding, adulteration results in discoloration and destruction of the leather in a much shorter time than when pure sumac is employed in tanning, and the money loss thus occasioned is many times the difference in cost between a pure and an adulterated sumac. Aside from any ethical consideration, there is absolutely no advan- tage to the tanner in the purchase of adulterated sumac because, as a matter of fact, the tannin in such sumac costs more for a given amount than when bought in pure sumac. Thus taking the current quota- tions of from $71 to $72 per ton for sumac containing 29 per cent of tannin, $70 to $71 for 28 per cent, and $69 to $70 for 27 per cent, the tannin costs from 12.2 to 12.4 cents, from 12.5 to 12.7 cents, and from 12.7 to 13 cents per pound, respectively. That is, the tanner is mak- ing a lower grade leather at a greater cost when using adulterated sumac. Finally, as there may be a variation of as much as 10 per cent in the tannin content of pure sumac, it should always be bought on the basis of its tannin content, and if adulterated should be so labele