considerable contamination with wood. Laboratory studies have indicated that a fairly good tanning extract can be made from the bark, and laboratory tanning tests have shown that this material can be used to tan heavy leather. The tanning properties of this extract differ from those of the woods-peeled bark extract. It penetrates more slowly and apparently is more astringent. The extract can be blended with other tanning materials and, in an emergency, could probably find a place in the tanning industry, but would not be rated equal to woodspeeled bark extract in quality. The prospects for the successful production of a commercial extract are not too bright but are definitely better than those for production of an extract from salt-water-floated bark.

(3) Salt water-floated hemlock bark.-Western hemlock bark from logs floated in salt water has been studied in the labotatory and in a commercial extraction test. This bark presents serious difficulties in handling. It has lost over half of its natural tannin during its floatation and has picked up appreciable quantities of salts. The salts cause precipitation of tannin and, if left in liquors and extracts, render them unsatisfactory for use. Partial removal of salt by cold-water washes causes additional loss in tanning and reduces further the possibility of economic leaching. The plant-scale tests for the production of an extract from salt waterfloated bark gave extracts that were entirely unsatisfactory because of their very low tanning content, low purity, and high insolubles.

(c) Researches with other vegetable tannins-(1) Canaigre.-Progress has been made in development studies of canaigre, which have been conducted in cooperation with the Bureau of Plant Industry, Soils, and Agricultural Engineering. Field plantings located in Texas, New Mexico, and Arizona have been made to study optimum conditions for growing. Canaigre can be raised as an annual crop. Yield studies indicate that an average of 10 tons of roots per acre can be expected when grown under favorable conditions. The fresh roots contain about 66 percent water. When dry, they contain approximately 20 percent tannin and varying amounts of starch and sugars. The roots can be cut and dried in the field, provided a large, clean drying surface is available. Because of the starches and sugars present, the production of high purity extracts presents difficulties. Sugars removed with the tannin produce low purity extracts and the presence of starch makes high temperature extraction of tannin difficult. By preliminary cold water extraction to remove sugars and moderately low temperature extraction to remove tannin, good tanning extracts have been prepared in the laboratory. Acceptable economic plant processes have not yet been developed. Successful tanning tests have been conducted in the laboratory using powdered canaigre root for tanning light leathers and preliminary tests in a commercial tannery gave promising results. Successful tanning of pieces of hide conducted in the laboratory indicate that canaigre can be used to produce an acceptable heavy leather. The development of procedures for satisfactory production of canaigre extract requires further study.

(2) Scrub oak bark from Florida.-There are about 20 species of scrub oak growing in almost solid stands in Florida, usually on submarginal sandy soil, according to a report by May and Frahm (Journal of the American Leather Chemists Association, 1943, p. 210). The stand covers an area of 5,000 square miles, as a conservative estimate; about 2,000 square miles is within the boundaries of national forests.

The most common type of scrub oak is the turkey oak. It is a small tree growing throughout the scrub oak forest. A preliminary survey by May and Frahm of a forest near Gainesville, considered to be representative of this type of forest in the State, indicated that an acre would yield about 9,000 pounds or 4.5 cords of bark, which contains approximately 12 percent tannin.

All of the oak forests are located in accessible areas. Due to the small diameter of these tress, it would be necessary to remove the bark by the use of drums or similar methods such as are now employed at the pulp mills for the removal of bark from slash pine. Such an industry could then be operated on a year-round basis. The oak wood would be a marketable byproduct for firewood, production of charcoal, or could be used for fuel in the operation of the extraction plants. At the Eastern Regional Research Laboratory, extracts from turkey oak having the following analyses were prepared:

Sole leather is being tanned with scrub oak extract and the indications are that a firm, well-filled piece of leather will be produced.

Tests on sheepskin and cowgrain skivers showed that the extract had good tanning quality and produced leather of desirable color.

(3) Mangrove bark from Florida.-The bank of the red mangrove (Rhizophora mangle) found in the swamps of Florida is known to be high in tannin. Samples taken in 1942 showed a tannin content ranging from 24.9 to 38.1 percent and indicated that the bark would make a satisfactory extract. However, the stand is limited in extent, the locations are accessible only by boat, and the trees are of moderate size. The expense of peeling the bark and de.ivering it to an extract plant probably would be prohibitive.

(4) Mineral tannages, such as alum, chrome, or zirconium, may be used to impart special properties to vegetable-tanned leather such as resistance to water or heat, or to increase resistance to abrasion. They can hardly be considered as replacements for quebracho except in the fact that by imparting longer wear to the leather, less leather and, hence, less tanning material would be required.

III

(a) (1) Weyerhaeuser Timber Co.-hemlock bark.-This company is conducting research on the preparation of a tanning extract from waste hemlock bark, a byproduct of their pulping operations. It is reported that they are contemplating the erection of a plant to produce tanning extract from salt water-floated bark containing as little as 5 percent tannin. Use of such bark does not appear to promise economic success.

(2) Leas & McVitty, Inc.-pecan shells.-The production of tanning liquors and extracts from pecan shells has been given some attention by Leas & McVitty, Inc. Only 12,000 tons of these shells are reported as being produced annually. Because of the limited supplies available and its low tannin content, it does not appear that this material will be of importance as a source of tannin.

(3) Mead Corporation and Leas & McVitty, Inc.-buttonwood extract.-An experimental lot of buttonwood extract has been manufactured by the Mead Corporation and is being used in tanning by Leas & McVitty, Inc. It apparently is a fair tanning material, but has the property of depositing sediment upon standing. This introduces problems in handling which would have to be overcome before this material could be considered as a partial replacement for quebracho. There is also considerable difficulty involved in gathering the bark. The available stands in this country may not be sufficient to justify serious consideration of this material as a potential source of supply.

(b) (1) Synthetic tannins.-It is difficult to determine this country's production of synthetic tannins, but it is small as compared with the amount of natural tannins. Syntans are usually derivatives of condensation products of naphthalene sulphonic acids, phenol suphonic acids, or similar products, and formaldehyde. Syntans as replacements for quebracho have the following limitations:

1. They do not give firm, well-filled leather. A possible exception is Orotan (Rohm & Haas).

2. They are expensive and require raw materials otherwise useful in war activities.

3. Their production at present is small as compared with quebracho and expansion would require greatly increased amounts of raw materials and production equipment.

(2) Sulfate cellulose. This material, known as spruce extract, super spruce extract, or lactanx (in which the sugars have been fermented to lactic acid) are used to a considerable extent in finishing operations. The laboratories of the Tanners Council at Cincinnati are experimenting upon its further modification. An increased amount of this material could possibly be used to replace quebracho in finishing operations upon leather, but objections 1 and 3 as applied to syntans would also apply here.

IV

If the quebracho supply were cut off for an indefinite period.—(a) The immediate effect upon the American tanning industry would be a marked modification of tanning blends in which an effort would be made to replace quebracho with those available tannins that most closely resemble this material. It is probable that the two materials that would receive first attention would be wattle extract and mangrove bark extract; and after these, oak bark and hemlock bark extracts. If any or all of these materials were available in sufficient quantities, an adjustment would be worked out in a reasonable time. The consideration of other potential but incompletely developed materials, such as western hemlock bark, canaigre, domestic mangrove scrub oak bark, and sumac would be decidely stimulated. 84949-44-pt. 9-4

(b) We would not be prepared to immediately substitute other materials for quebracho. If it should become necessary to completely replace quebracho with other tannins, serious difficulty would be encountered. Sufficient equipment is not available to produce domestic extracts in quantities equivalent to the quebracho extract now imported. The construction of the additional extract plants, involving the use of critical metals, would become an important problem.

V

German experience with tanning materials.-A survey of the chemical literature for the past 3 years indicates that the attention of tannery technicians in Europe has been directed to the following lines of work: (1) Development of syntans, (2) improvement of pine-bark extract, (3) improvement of sulfite cellulose, and (4) conservation and recovery of chromium.

The yield of tanning extract from pine bark can be increased by the use of sulfite. Extraction of pine bark with solvents other than water and with special equipment has been investigated.

A number of substitution syntans or syntans that can replace vegetable tannins have been developed. It is claimed that leathers tanned with these syntans alone have been produced that were equal in tensile strength, feel, and softness to vegetable-tanned leather. In suitable combinations, they may replace up to 50 percent of the natural tanning materials, and regulations require that at least 30 percent of synthetic tanning materials must be added to all natural extracts in ordinary cases. These synthetic materials are said to be better than sulfite cellulose extracts.

Savings in imported tanning extracts have also been obtained by increased use of indigenous materials of natural origin. In addition to pine bark, oak and fir barks are used in Germany. An unsuccessful attempt was made to increase the yield of tanning from oak wood and pine bark by a preliminary heat treatment. Cultivation of badan in Germany has shown that a satisfactory product can be produced from that plant and that the yield per acre is about eight times that from oak bark.

In 1940 it was reported that profound changes in tanning processes in Czechoslovakia had been made necessary by diminished supplies of quebracho extract. French tanners, according to another report, are forced to use substitutes for quebracho and are investigating oaks, various other trees, and vegetables.

The bark of American pines is low in tannin. One sample of long leaf-pine bark from Florida contained 8.2 percent of catechol-type tannin. A sample of slash pine bark from Georgia contained 5.9 percent tannin and barks from short-leaf pine from southern Maryland contained from 4.8 to 7.8 percent of tannin. The purity of pine-bark extract would be low.

TABLE 1.—World's consumption of Argentinean and Paraguayan Quebracho extract

From The Quebracho Extract Industry, Its Importance in Argentina and Paraguay, in the Leather Trades Review, issue of July 21, 1943.

TABLE 2.—Imports and domestic production of vegetable tanning materials for the United States leather industry, 1937 to 1942, inclusive

TABLE 2.—Imports and domestic production of vegetable tanning materials for the United States leather industry, 1937 to 1942, inclusive-Continued

1 Percentages of tannin content shown in parentheses were used for the calculations of tannin for the years 1937 and 1938.

Tannin is reported in tons of 2,000 pounds.

3 Production data were secured from the U. S. Tariff Commission and the American Extract Manufac turers Association and were used in calculating the percentages shown.

The import data were secured from the U. S, Tariff Commission and have been used in calculating the percentages shown.

Not separately reported.

100.00 152, 203

100.00