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Green plants manufacture sugars so that they all contain some quantity of sugar. However, much of the manufactured product is used directly in plant metabolize that very little usually accumulates. Storage sugars are found in roots, as with beets, carrots, parsnips; in stems as in sugar cane, sorghum, maize and the sugar maple; in flowers, such as in palm trees; in bulbs like the onion; and in many fruits. There are several kinds of sugar, principal among which are sucrose or cane sugar, glucose or grape sugar and fructose or fruit sugar. They all seem to serve as a reserve food supply for the plant.
Humans require sugar in their diet. It constitutes a perfect food, as it is a form that can be readily assimilated in the body. Its main value is as an energy producer, and it is especially well adapted for use after heavy exercise. A large industry has developed in connection with the extraction of sugar from plant tissues, purification and refining. Additionally over 10 thousand different chemical derivatives have been made.
Sugar is an especially valuable product derived from the plant world. Only wheat, maize, rice and potatoes surpass it in importance. Yet there are relatively few sources for this industry. Only the sugar cane, sugar beet, sugar maple, maize, sorghum and several palms are commercial sources. Sucrose is the type of sugar stored in all of these plant species.
Most sugar is derived from sugar cane, Saccharum officinarum. It is a vigorous and rapid-growing perennial grass reaching a height in cultivation of 8-12 ft and a diameter of about 2 in. It grows in clumps with bamboo like stems arising from large rootstalks and with very ornamental feathery plumes of flowers. The stem is solid with a tough rind and numerous fibrous strands, and contains about 80 percent juice, the sugar content of which varies considerably from area to area and season to season.
Commercial sugar cane is a cultivar that is not known in the wild state. The plant was most likely first domesticated in Southeastern Asia or the East Indies from some wild ancestor from that region. By 327 B.C. it had become an important crop in India. It reached Egypt in 641 A.D. and Spain in 755 A.D. Since that time sugarcane has gradually been introduced into most humid tropical and semitropical regions. The Portuguese and Spaniards were great disseminators of the plant into the New World. They carried it to Madeira in 1420 and to America by the beginning of the 16th Century. Within another 100 years it had spread all over the West Indies, Central and South America. Sugar cane first arrived in the United States in Louisiana in 1741. The name “sugar” is derived from Sanskrit “sarkara,” meaning gravel, and refers to the crude sugar, which was the only kind known for centuries.
Sugar cane has been the principal export crop of the tropics and is unaffected by many of the conditions that influence the growing of other crops. It will grow well in any moist hot region where the average rainfall is 50 in. or more per year and where there is abundant sunshine and where temperatures do not drop below 70 deg. Fahrenheit. Backyard stands of sugar cane are possible in colder climates, however. Cultivation styles vary considerably, but in general extensive, flat, low-lying fields are utilized and these are plowed deeply. Cuttings of varying length made from the upper joints of old canes propagate the sugar cane. These cuttings, known as seed, are placed in trenches and nearly covered with soil. They begin to sprout in about two weeks. When the cane is grown for human consumption, the cuttings are usually placed in holes. The crop has to be cultivated, weeded and fertilized extensively during the first few months. It is harvested from 10-20 months after sprouting. Harvest is 10-20 months after sprouting. The sugar content is carefully monitored and the canes are cut at just the right stage. This is usually when the flowers are beginning to fade. The stems are cut close to the ground because the lower end of the cane is richest in sugar. Cane knives have been ordinarily used in poorer countries. The rhizomes normally give rise to two or three more crops, known as ratoons, before another planting is required. There have been up to 20 ratoon crops obtained, however.
Cultivated varieties today are usually hybrids of Saccharum officinarum, the “noble cane,” with other hardier species.
Sometimes small owners of a stand of sugar cane extracted their own sugar in a primitive mill, but more often large “centrals” have been established which draw their supply from a wide area. In the milling process the canes are first carried to crushers where they are torn into small pieces. They are then passed through three sets of rollers. In the first set 2/3rds of the juice is expressed. They are then sprayed with water to dilute what sugar remains, and are passed through the second set. These rollers exerts a very high pressure and remove nearly all of the moisture. After passing through the last set the residue is almost dry. This bagasse, as it has been named, can be used as a fuel for the mills, as a source of paper or wallboard because of its fibrous nature. It also contains a wax with some commercial value.
The juice that flows from the mill is a dark-grayish sweet liquid full of impurities. It contains sucrose, and other sugars, together with proteins, gums, acids, coloring materials, soil and pieces of cane. The purification of the sugar involves the separation of the insoluble materials and the precipitation of the soluble nonsugars. The juice is first strained or filtered to remove the solid particles. It is then heated to coagulate the proteins, a process which is aided by the addition of sulfur. Lime is then added to neutralize the acids present, to prevent the conversion of sucrose into lower carbon sugars and to precipitate some of the substances in solution. These are removed by a series of filter bags or a filter press. Carbon dioxide may be added to aid in the process. The chemical processes involved in the purification of sugar are under constant supervision. The juice is now clear and dark colored and ready for concentration. It is boiled down to a syrup of such density that the sugar crystallizes out. This operation is done in open kettles or vacuum pans. The resulting sticky mass is known as massecuite. It is placed in hogsheads with perforated bottoms. The juice slowly percolates through the holes leaving the crystals of sugar behind. The juice constitutes the familiar molasses of commerce. In modern refineries the massecuite is centrifuged with the molasses passing out through fine perforations. The raw or crude sugar thus obtained is brown in color and 96 percent pure.
Besides the bagasse, by-products of value are molasses, which is used in cooking and candy making. It is also used in the manufacture of rum and industrial alcohol. The better grades of molasses are obtained when the cruder methods of sugar milling are employed, for in such cases the sugar content of the molasses is higher. A mixture of bagasse and molasses, known as molascuit, is a valuable cattle feed.
Refining is the final stage of sugar preparation for markets. This is usually done in factories located in seacoast areas of the United States and Europe. The process involves washing to remove the film of dirt from around the crystals of crude sugar, dissolving the sugar in hot water, the removal of any mechanical impurities by filtering through cloth, decoloring by passing through bone black, recrystallization by boiling, and the removal of the liquids from the granulated sugar by centrifuging or other means. A hundred pounds of raw sugar usually yields 93 lb. of refined sugar and three-quarter gallon of refined molasses. The granulated sugar is washed, dried, screened, and packed. Loaf, cube and domino sugars are made by treating granulated sugar with a warm concentrated sugar solution and pressing it into molds. Loafsugar is often sawed into blocks, strips or other forms. Powdered sugar is made from loafsugar or imperfect pieces of other types by grinding, bolting and mixing with starch to prevent lumping. The refining of sugar is a very old process and was probably first done in North Africa. The first type of refined sugar was the sugar loaf, which appeared in England in 1310 and was familiar in America until late in the 19th Century.
A marketable syrup has also been made from sugar cane by clarifying the juice and merely evaporating it to a consistency where the water content is 25-30 percent. This is sometimes called Golden Syrup.
India led the production of cane sugar in 1947, raising about 25 percent of the world’s crop. Cuba, Brazil, Puerto Rico and other islands of the West Indies and Australia followed in the order names. In the United States Louisiana, Florida and Texas produce most of the sugar. The highest yields per acre have been recorded in Mauritius.
<bot335> Bananas (Musa sapientum ) (fruit; fiber) & Sugar Cane (Saccharum officinarum) in northern Costa Rica
Sugar beet, Beta vulgaris, is another important source of sugar. It was derived from the wild B. maritima, which is still found wild on European seacoasts. There were times when beet sugar equaled or even exceeded that of cane sugar. However, by the 21st Century only about one-third as much beet sugar as cane sugar was being produced.
Although sugar beet was known since before the Christian era it was not used as a source of sugar until modern times. The leaves are edible as a substitute for spinach and the cooked beet serves as a delicious vegetable. The occurrence of sugar in the tubers was first noted in 1590 but Maregraf in 1747 first realized its possibilities. The industry formally began around 1800 in both Germany and France. Napoleon promoted the use of it as an embargo against British importations. He was ridiculed because of this and a famous cartoon pictured him dipping a sugar beet into his coffee. Another cartoon showed him offering one to his small son, the King of Rome, with the caption, “Suck dear, suck, your father says it’s sugar” (Hill 1952). Subsequently interest in sugar beets decreased, but it was again revived in France around 1829 and in Germany in 1935. Since then it has been a crop of increasing importance in many European countries. Although earlier attempts were made, the beet industry did not truly begin in the United States until 1879.
Sugar beet is a white-rooted biennial that grows best in regions where summer temperatures range around 70 deg. Fahrenheit. It produces well in irrigated portions of the southwestern United States during winter months. Almost any good soil is suitable for this plant’s growth. Plants are frown from seed and must be thinned until they are from 8-10 in. apart. Thorough weeding and deep cultivation are required. The crop is easily machine cultivated and harvesting, so is less expensive to raise than sugar cane. In temperate climates the seeds are sown inn April and the roots are allowed to remain in the ground until October because the sugar content increases in that position. The beets are pulled before the ground hardens and the tops are removed to prevent loss of sugar after which they are stored. The finest plants are saved for seed, which has led to a gradual improvement, by selection.
Extraction of the juice is a simpler process than for sugar cane because the roots are soft and pulpy. Earlier they were rasped to a pulp and the juice squeezed out in bags, but then a diffusion process was used. The roots are cleaned, cut into thin strips and heated in running water in a series of tanks. About 97 percent of the sugar can be extracted in this manner. The waste beet pulp is removed and a process known as carbonation precipitates the insoluble impurities in the raw juice out. For this the raw juice is treated with lime, which coagulates some of the nonsugars, and carbon dioxide, which precipitates calcium carbonate. This settles out along with the impurities and the purified juice is separated out by filtration. The process is repeated several times during which sulfur dioxide is added to adjust the alkalinity. A clear liquid is left after filtration, which is concentrated, crystallized and centrifuged just as with cane sugar. The massecuite is reboiled several times. It is difficult to differentiate between raw beet sugar and raw cane sugar for they are for all practical purposes identical in composition and appearance. By-products of the industry include the green tops, which are used for cattle feed and fertilizers; the wet or dried pulp, which is a valuable cattle and sheep feed; the filter cake, which is used as a manure; and the molasses, which is used for stock feeding or for industrial alcohol.
Central Europe has produced most of the beet sugar, while in the United States California, Colorado and Idaho are the principal states that grow this crop. It might be noted that in the manufacture of rum in Europe, the flavor when the rum is derived from beet sugar differs substantially from that prepared from sugar cane. The former tends to be much more aromatic and has a distinctly unique taste
<bot701> Sugar beet roots (Beta vulgaris) [Mediterranean]
The sap of maple trees is used in making syrup and sugar. The area is confined to northeastern North America and was discovered and developed by the Amerindians.
Although several species of maple have a sweet sap, the most important is the sugar maple, Acer saccharum, and the black maple, A. nigrum. The sugar maple is a prominent tree in the northern part of the eastern deciduous forest zone. It reproduces naturally and lives to an age of 300-400 years. The red and silver maples give a comparatively small yield and are not of commercial interest. The sap begins to flow about the middle of March and continues for about a month. This is a period of warm, sunny days and cold nights. The best flow comes when the temperature reaches 25 deg. Fahrenheit at night and 55 deg. Fahrenheit during the day. The preferred location for tapping is the first three inches of sapwood, about 4.5 ft. above the ground.
Amerindians made incisions in the bark or large roots and conveyed the sap by reeds or curved pieces of bark into clay or bark receptacles. They boiled down the sap by dropping hot stones into it and converted the sap into sugar by letting it freeze and skimming off the ice. European settlers were quick to adopt the procedure and they added many improvements, eventually tapping with a 1-inch auger and using spiles to convey the sap into containers. They evaporated the sap in the open in large kettles so the sugar had many impurities. The dark-brown sap was stored and later converted into sugar. This involved the famous sugaring-off, a process in which the syrup was boiled until it became waxy and the container was then dropped into snow. It was then poured into molds, where it immediately crystallized. Such simple methods are persisted for domestic use.
Commercial production further advanced the technique. Modern evaporators have replaced the furnaces and oiling pans of earlier times. These are able to convert from 25-400 gallons of sap into syrup in one hour. Great improvements have also been made in cleanliness and in the methods of collecting and transporting the sap. Such large operations involve from 100-1,000 trees. A well-managed sugarbush has about 70 trees to the acre, which allows room for the development of individual trees.
The maple-sugar industry reached its peak in 1869 when 45-million pounds were produced. With the advent of cane sugar it ceased to be an important commodity. Today the product is very pure and the demand is increasing for the syrup especially. Southeastern Canada is the leading producer while in the United States Vermont, New York, Ohio, Michigan and Wisconsin produce small amounts.
<bot700> Maple (Acer saccharum) tapping in February [NE North America]
Several species of palm provide a fourth source of commercial sugar all of which is only available in the tropics and subtropics. The species utilized are the wild date, Phoenix sylvestris, the palmyra palm, Borassus flabellifer, the coconut, Cocos nucifera, the toddy palm, Caryota urens, and the gomuti palm, Arenya pinnata. Some of the oil palms also yield sugar. The date palm is tapped similar to that of a maple and the sap is obtained from the tender upper portion of the stem. In the other palm species the sap is secured from the unopened inflorescences. Usually the tip of these is cut off and the sap oozes out and is collected in various containers. The yield of this sweet juice, known as toddy, amounts to 3-4 quarts per day for a period of several months. The sap has a sugar content of about 14 percent. It is boiled down to a syrupy consistency and poured into leaves to cool and then hardens into the crude sugar known as jaggary. Some of this has reached European markets. Three quarts of juice yield about one pound of sugar. The toddy is often fermented to make the beverage known as arrack. The palm sugar industry is very old in India where over 100,000 tons were still being produced yearly by the mid 1900’s.
The stem of the sweet sorghum, Sorghum vulgare var. saccharatum, contains a juice that is used in making syrup. To differentiate between a true syrup and a molasses it is necessary to realize that syrup is the product obtained by merely evaporating the original plant juice so that all the sugar is present. On the other hand, molasses is the residue left after a juice has been concentrated to a point where much of the sugar has crystallized out and been removed. The sweet sorghum or sorgo is a wild plant of the tropics and subtropics which ahs long been cultivated in many parts of the world. The juice is a poor source of sugar, but yields nutritious and wholesome syrup. The stems are easily crushed and the juice is evaporated in shallow pans. On the average about 11-million gallons were being made in the United States by the mid 1950’s. Similar syrup has also been made from sugar cane by clarifying the juice and evaporating it to a consistency where the water content is 25-30 percent.
This sugar is also known as dextrose or grape sugar. It is present in small amounts in many of the organs of higher plants and is especially characteristic of fruits. However, commercial glucose is prepared from starch.
Also known as levulose, this fruit sugar is present in many fruits together with glucose. It is somewhat sweeter than cane sugar and is valuable because diabetics can consume it. Commercial fructose is prepared from inulin, a polysaccharide that occurs in the tubers of the dahlia, Dahlia pinnata, the Jerusalem artichoke (= sunchoke), Helianthus tuberosus, and some other plants
Mannose does not occur free in nature so that it must be obtained by hydrolysis from several complex compounds. It is readily oxidized from the juice of the manna ash, Fraxinus ornus, a tree in Sicily and southern Europe. The juice oozes from slits made in the bark and dries into a very sweet flakelike material known as manna. Its use is primarily in medicine.
Maltose is also rarely found in a free state in plants, but is easily produced from starch through the activity of the enzyme diastase. It is used primarily in the brewing industry. Maltose syrup is sometimes used as a substitute for glucose and in medicine. Maltose that is obtained from rice starch has been used in Japan as a flavoring for over 2,000 years.
Flowers that are attractive, such as roses, hibiscus, etc., usually produce a sweet substance called nectar. This serves to attract various insects that are necessary for pollination of the plant. Nectar is composed mainly of sucrose with some fructose and glucose. It is used as food by bees, and some of it, after partial digestion, is converted into honey and stored for future use. During this process the sucrose is changed to an invert sugar, which is a mixture of fructose and glucose. Honey contains 70-75 percent invert sugar along with proteins, mineral salts and water. The sugar has a tendency to crystallize out. Honey was most likely the first sweetening substance used by humans. Beekeeping is one of the very oldest industries. The flavor and quality of honey vary depending on the source of the nectar. Flowers that contain essential oils impart a typical taste. The bees favor certain plants and these are often cultivated near the apiaries. Clover, Alfalfa, buckwheat, lindens and some of the mints and citrus are among the favorites. Honey is an excellent food for it is almost pure sugar. It is also used in medicine, in the tobacco industry and in the manufacture of a fermented beverage called mead.
One of the most important and widely available vegetable products, starch constitutes the principal type of reserve food for green plants. It is a complex carbohydrate. It is stored in thin-walled cells in the form of grains. There are several types of starch that differ in the size and shape of the grains and other physical and microscopic characteristics. Important sources of starch are the cereal grains and underground tubers, although nuts, legumes and other plant organs may contain substantial amounts. Besides being a staple food for animals and humans, it also has many industrial applications.
Soluble starch is a form that is used in the textile industry to strengthen the fibers and cement the loose ends thus making a thread that is smoother and easier to weave. It also gives a finish to the end product. It serves as a mordant in calico printing, a thickener for the colors. Starch is also used as a sizing agent in paper industry, in laundry work, in medicine, in the preparation of toilet powders, as a binding for china clay and as a source of many other products.
Relatively few plants are used for the commercial production of starch. The main ones are potato, maize, wheat, rice, cassava, arrowroot and sago.
Maize or Indian corn is the source of over 80 percent of the starch that is made in the United States. The grains are soaked in warm water with a small amount of sulfurous acid to loosen the intercellular tissue and prevent fermentation. Then the corn is ground so as not to injure the embryos. The ground material is placed in germ separators where the embryos are removed. The starch material is then ground very fine and is either passed through sieves of bolting cloth or is washed in perforated cylinders to remove the bran. The resulting milky liquid is run onto slightly inclined tables where the starch grains settle out and the remaining material flows off. The starch is later collected and dried in kilns and is then ready for the market. The best grades of cornstarch are used for food while inferior grades are for laundry starch and sizing and as a basis for glucose.
Cull potatoes are utilized for making starch. These are washed and reduced to a pulp in graters or rasping machines. The resulting paste is passed through sieves to remove fibrous matter. After washing the solid starch is separated by sedimentation, the use of inclined tables, or centrifuging, and is then dried. Potato starch finds uses in the textile industry and as a source of glucose, dextrin and industrial alcohol. Europe is the principal producer.
The oldest commercial sources of starch were from wheat. It was known to the Greeks and was widely used in Europe in the 16th Century in connection with the linen industry. The gluten in wheat makes the removal of the starch a difficult process. It is accomplished by extraction with water or by the partial fermentation of the grain. Wheat starch is used mostly in the textile industry.
Rice grains that are broken or imperfect are used for making rice starch. These are softened by treating with caustic soda and are then washed, ground and passed through fine sieves. More alkali is added and after a time the starch settles out as a sediment. This is removed, washed and dried. Occasionally dilute hydrochloric acid is used to free the grains. Rice starch has found use in laundry and for sizing.
Cassava flour and tapioca are used in industry mainly as sizing materials and as the source of certain starch products.
The tubers of several tropical plants provide a source for arrowroot starch. West Indian arrowroot is from Maranta arundinacea. Florida arrowroot is from Zamia floridana. Queensland arrowroot is from Canna edulis, and East Indian arrowroot from Curcuma angustifolia. The tubers of these plants are peeled, washed and crushed and the pulp passed through perforated cylinders. A stream of water carries the starch into tanks where it settles out. Arrowroot starch is easily digested and thus is valuable as a food for children and invalids. There is little use in industry.
The stems of the sago palm, Metoxylon sagu, contain starch. Cultivation is in Malaya and Indonesia. The flowers appear when the trees are about 15 years old and just prior to this time the stems store up a large amount of starch. The trees are felled and the starch pith is removed. This is ground up, mixed with water and strained through a coarse sieve. The starch is freed from the water by sedimentation and washed and dried. This is known as sago flour. Commercial sago is prepared from this by making a paste and rubbing it through a sieve in order to cause granulation. The product is dried in the sun or in ovens and appears as hard shiny grains, known as pearl sago. Both sago starch and pearl sago are used almost entirely for human consumption.
Starch grains are insoluble in cold water but they readily swell in hot water until they burst to form a thin, almost clear solution or paste. This soluble starch has been used for finishing textiles and in the paper industry.
When starch is heated or treated with dilute acids or enzymes it becomes converted into a tasteless, white, amorphous solid known as dextrin or British Gum. Dextrin possesses adhesive properties and has been used as substitutes for mucilage, glue and natural gums. Bread loaves brushed with dextrin aids in crust formation. In steel manufacture, the sand for the cores used in casting is held together with dextrin. Other uses include cloth printing, glazing cards and paper and making pasteboard.
When starch is treated with dilute acids for a long time it becomes more completely hydrolyzed and is converted into glucose sugar. Often the same factory that extracts the starch also converts it into glucose. This operation is done in large copper boilers under pressure. About six pounds of dilute hydrochloric or sulfuric acid are used for each 10,000 pounds of starch. After all the starch has been converted, the free acids are neutralized with caustic soda. The liquid is then decolorized with boneblack and concentrated into thick syrup. One of the common brands of corn syrup is “Karo.” Glucose may be considered as an inferior substitute for cane sugar. However, it is an excellent food material. Its use is in table syrup, for sweetening, in candies, jellies and other kinds of cooking. It is often mixed with maple syrup, brown sugar, honey or molasses it is used for making vinegar and in brewing.
Starch is the source of an enormous quantity of industrial alcohol. Maize and potatoes constitute the chief sources, although the other starches and even cellulose, various products of the sugar industry and fruit juice may be utilized. The process converts the starch into sugar by means of diastase and the fermentation of the sugar by yeasts to yield alcohol. The operations are carried out under different conditions from those followed in making alcoholic beverages. When fermentation has stopped, the alcohol is extracted from the mash by fractional distillation. The alcohol thus formed as a result of the fermentation of sugar is known as ethyl alcohol, as distinguished from methyl or wood alcohol, a product of the destructive distillation of wood. To render it unpalatable, ethyl alcohol is often “denatured:” by adding methyl alcohol or other substances. Industrial alcohol is the most important and most widely used solvent and is the basic material in the manufacture of hundreds of products. It is also used in medicine, pharmacy and other industries.
Starch and cellulose are chemically very similar products. Cellulose reacts with nitric acid to form nitrocellulose while starch yields nitro starch. Nitrostarch is a very safe explosive if the ingredients are absolutely pure. Tapioca starch was originally imported for this purpose but during World War I cornstarch was used as a source.
The most complex of the carbohydrates, cellulose is present in the cell walls of all plants. Because of their strength, cells with thick walls have been used in various industries. Besides the natural product being used in the textile industry, artificial fibers are derived directly from cellulose as well as countless other products. Cellulose chemistry is an important phase of organic chemistry.
Cotton, a very pure form of cellulose, has been used for a very long time in the production of artificial fibers and other cellulose products. Wood is another very available source. When certain woods are treated with concentrated acids or alkalis, the bond between the wood fibers and the lignin, which cements them together, is broken, and the fibers, which are pure cellulose, can be removed. These fibers may then be reorganized as paper, or they may be treated further chemically. If the chemical treatment merely causes the dissolution of the fiber into its component molecules, these molecules may be synthesized into artificial fibers or converted into cellulose plastics. But if the molecules themselves are broken down, their component elements, carbon, hydrogen and oxygen, may be recombined to form wood sugar. Thereafter the wood sugar may be transformed into yeast or alcohol and thus become available for food or as the raw material for numerous industrial products.
A very important use of cellulose is in the manufacture of paper, a very old industry. The word “paper” comes from the Latin “papyrus” the name of a sedge, the pith of which was used for paper in 2400 B.C. Egypt. However paper was first made in China. The industry spread from China to India, Persia and Arabia and then through Spain to other European countries. The first paper mill in the United States was in 1690 at Philadelphia.
The papermaking value of the various fibers depends on the amount, nature, softness and pliability of the cellulose present in the cell walls. This cellulose may occur alone or in combination with lignin or pectin. Wood fibers, cotton and linen are the principal raw materials.
Wood began being used in the paper industry from about 1850. Today wood has largely replaced the other fibers and furnishes over 90 percent of all the paper manufactured in the Untied States.
Spruce is a very important source of wood pulp and has furnished about 30 percent of the total supply. It is ideal because it has all the requirements of a good pulpwood. The fibers are long and strong with a maximum content of cellulose. The wood is almost free from resins, gums and tannins; and it is light colored, sound and usually free from defects. Red spruce, Picea rubens, white spruce, P. glauca and Sitka spruce, P. sitchensis, are the main species
The southern yellow pine, Pinus australis, is another important pulpwood. The eastern hemlock, Tsuga canadensis, is a main species in the Lake States while the western hemlock, T. heterophylla is important on the Pacific Coast. Other species include aspen, Populus grandidentata and P. tremuloides, and balsam fir, Abies balsamea. Of lesser importance are jack pine, Pinus banksiana, tamarack, Larix laricina, white fir, Abies concolor, and several hardwoods among which are the beech, Fagus grandifolia, sugar maple, Acer saccharum, and birch, Betula lutea. Sawmill waste is also an increasingly valuable source of wood pulp.
Up to the middle of the 19th Century rags of cotton and linen were the only source of paper, and they are still used for making the finest grades. Cotton fibers have a high felting power and a high cellulose content of about 91 percent. Rags and raw cotton in the form of fuzz or linters are utilized. Flax fibers, that comprise linen, contain 82 percent of pectocellulose and yield a paper of great strength, closeness of texture and durability. Textile waste may also be used. In the preparation of rag pulp the material is sorted, cut into small pieces and freed from dust. It is then boiled in caustic soda to remove the grease, dyes and other impurities and it is washed until perfectly clean. The resulting pulp is used directly in papermaking.
Esparto grass, Stipa tenacissima, is important in Great Britain. The plant is native to Northern Africa where it flourishes in dry, sandy and rocky coastal regions. The tufted wiry stems are plucked and pressed into bales for shipment. Esparto is converted into pulp by heating in a caustic coda solution under pressure. Although the cellulose content is only 48 percent, the fiber has great flexibility and felting power. It yields an opaque, soft, light paper of uniform grade. The finest printing papers in England have been made from esparto, either entirely or in a mixture. Another grass, Lygeum spartum, is also used.
There are other textile fibers other than cotton and flax that have been used as sources for paper. The waste material of the jute and hemp industry, in the form of old ropes, sacking, sailcloth, etc. was once used extensively for making strong and tough papers. Jute and jute butts were used mainly for wrapping paper, envelopes, cable insulation, while hemp, after bleaching, yielded ledger and bank-note paper. Manila hemp was an important source of envelopes and wrapping paper. Ramie, sisal, sunn hemp, New Zealand hemp, coir and other fibers have been utilized.
The bast fibers of the paper mulberry are very strong and have been used in Japan for paper lanterns and umbrellas and as paper for writing. The fiber is scraped, soaked and beaten, after which it is mixed with mucilage and spread on frames to dry. When treated with oil this paper becomes strong enough to serve as a substitute for leather or cloth.
There are many other sources for making paper than what has been noted previously. For example, stems of rye, barley, wheat, oats, rice and other grasses are used for low-grade paper, strawboard, pasteboard and cardboard. These plants have fibers with low cellulose content and are too short and small to have much tensile strength. Thus, they are mixed with other fibers. Sugarcane bagasse, cornstalks, and waste paper have been developed as sources of paper. Banana fiber, tree bark, rushes, weeds, broomroot, licorice, cotton and tobacco stalks, beet pulp waste and peat have been used somewhat. Recycled paper is extensively used to make other paper products.
In the Orient bamboo fiber is an important source of paper. The papyrus, Cyperus papyrus, baobab, Adansonia digitata, and Daphne cannobina are used in Africa and India. Rice paper of Japan and China is made principally from Tetrapanax papyriferum, Edgeworthia tomentosa or Wickstroemia canescens.
Hill (1952) writes that since the Middle Ages until modern time there have been many schemes to make artificial silk and other fabrics. In 1880 Count de Chardonnet made the first artificial fiber, and a few years later the first artificial silk. Later factories were established for making the product. At the outset this new material was handicapped by its name for the public considered it only as an imitation or a substitute. This condition existed as late as 1908. Today it is understood that all the artificial fibers constitute entirely new products with valuable characteristics and properties of their own.
The raw material of the rayon industry is high-polymer alpha cellulose, prepared in a pure form from wood pulp or cotton linters. Purification is accomplished by the elimination of mechanical impurities through air separation and then cooking in a 3.5 percent sodium hydroxide solution. This removes all the other organic substances. The pure cellulose fibers that remain are bleached, washed and dried. The next step is to dissolve the cellulose by various solvents thus rendering it sufficiently liquid so that it can be squirted in a fine jet. The solution is then forced by pressure through minute perforations in glass or platinum, and emerges from these “spinnerets” in thin streams. The streams are coagulated into fine, almost invisible filaments in different ways. The solvents are removed and the filaments are caught up by revolving reels and twisted into threads suitable for spinning. The threads are washed, bleached and dried. In the viscose, nitrocellulosee, and euprammonium processes the final product is an almost pure cellulose fiber known as regenerated cellulose. This is chemically identical with the cellulose in cotton, but it differs in itss mechanical properties. The product of the acetate process is a cellulose ester , cellulose acetate. This differs from regenerated cellulose in both its chemical and physical properties.
Treatment with concentrated nitric acid in the presence of sulfuric acid causes cellulose to change into several types of cellulose nitrate. These differ according to which concentration of nitric acid was used and the consequent degree of nitration as well as the temperature and the duration of the action. The higher cellulose nitrates are called guncotton, or in error nitrocellulose. The lower nitrates constitute pyroxylin, or collodion cotton.
This is made from cotton linters during which process the cellulose is completely nitrated. It is used as an ingredient of many high explosives. Cordite, e.g., is a combination of guncottton and nitroglycerin, while smokeless powder is made from a mixture of guncotton and the lower nitrates. Guncotton is one of the safest of explosives to handle when properly manufactured.
A partial nitration of cellulose produces pyroxylin. This is carried out under different conditions from those, which result in the formation of guncotton. In modern photography the films often consist of pyroxylin coated with gelatin. It is used in the rayon industry. However, its chief value is that it is soluble in a variety of solvents and yields many useful products, such as celluloid and other plastics, collodion, artificial fabrics and varnishes.
Industrial uses include as a substitute for cellulose nitrate in the film industry because it is not very flammable. Resultant films are more brittle and expensive, however. It is also used for goggles, gas masks, automobile windows, artificial fabrics, index cards, airplane varnish, etc.
Cellophane is a viscose product. Forcing crude viscose through tiny slits rather than perforations makes this. It coagulates into a thin transparent film only one-thousandths of an inch in thickness. Such viscose files are used for numerous poses even for sausage casings. Viscose fibers have replaced cotton in Welsbach mantles.
When cellulose is completely hydrolyzed in a process of saccharification this ultimately results in the conversion of the cellulose into wood sugar that in its turn yields alcohol and yeast. It is a complement to the manufacture of paper pulp from wood.
Under usual processes of pulp making one ton of wood is converted to one-half ton of pulp and enough wood sugar to yield 10-12 gallons of alcohol. Doubling the cooking time produces an edible starchy material that is an excellent cattle feed, and sufficient sugar to furnish 20 gal. of alcohol is obtained. Under a still longer cooking time all of the cellulose can be converted into sugar with an eventual production of 60-80 gal. of alcohol.
Regarding the kinds of wood sugar that are produced, conifers yield glucose, pentose, and mannose; hardwoods glucose and pentose. These sugars are useful because they can be readily fermented.
Glucose and mannose, which comprise about 2/3rds of the wood sugar, are converted into ethyl alcohol by the action of ordinary yeast. This industrial alcohol has a wide range of uses. Pentose sugars are not fermentable into alcohol, but they can be converted, through the activity of a bacterium, Torulopsis utilis, into Torula yeast, and edible substance with a 50 percent protein content. One ton of pulp will yield from 40-100 lbs. of yeast.
Cellulose hydrolysis can play an increasing role in a well-organized system of forest utilization as it eliminates much of the waste. Small pieces of wood, chips, sawdust, wood flour and sawmill waste can all be used effectively
Many tropical plants have seeds that are very thick, hard and have heavy walls consisting of hemicellulose. This is a modification of ordinary cellulose and constitutes a supply of reserve food for the plant. In young seeds the endosperm consists of a milky juice, but as the seeds mature this fluid is replaced by the harder material. hemicellulose cannot be used by animals as food. However, it does provide vegetable ivory of commerce.
The Ivory-nut or Tagua Palm, Phytelephas macrocarpa, of the Neotropics is the main source of vegetable ivory. The palm is a low0-growing tree typically on riverbanks from Panama to Peru. The drupes like fruits have from 6-9 bony seeds with a thin brown layer on the outside and a very hard and durable endosperm. The natives collect the seeds that are shipped to Europe and the United States. Ecuador is the main exporter. This ivory may be carved and shaped into various objects, so it serves as a substitute for true ivory in the manufacture of buttons, poker chips, knobs, chessmen, dice, inlays, etc.
Several species of palms in Africa and Polynesia and Neotropical America have seeds of similar constituency. With the exception of Metroxylon amicarum of the Caroline Islands, these are not important in commerce.