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chemical composition. .Aside from these elements which enter into life processes there is hardly a single element or a single raw material of which we can safely say that its disappearance would harm mankind or seriously retard his progress in civilization. These other things may be conveniences but are not necessaries. We have gone beyond the point where the disappearance of this or that little pocket of material collected and stored in the distant past would be fatal to our progress. Difficult periods of adjustment there might be for a generation or so, but nothing more. Role of the Chemist Of the four general causes or methods which lead to the conversion of waste into by-products, the one labeled “Legal Action” is to my mind by far the most important, and the one called “Special Demand” is next. The third one is rather unimportant, and the fourth one is difficult to place. This steady work of organization has a tremendous importance, but whether its net results are larger or smaller than those of the other two is difficult to say. As a matter of fact the progress by “Legal Action” and the progress by “Special Demand” are very generally made in the research organizations of large corporations. This whole question of wastes as a source of by-products or of raw materials is not so impressive to me as it is to many chemical men. The mere fact that a constant stream of chemicals is going to waste from a plant into the air or into the river does not make me nervous. They probably should go there. If there is a strong enough demand for these chemicals to pay for their recovery, rest assured they will ultimately be recovered. Or if legal action impends, rest assured proper action will be taken. In the absence of proper
Vol. 18, No. 11
market or of legal action let them go to waste as they should. The great contribution of the chemist to mankind, in my opinion, does not especially lie in his recovery of wastes but rather in freeing man from the tyranny of raw material. For most purposes man requires certain qualities or properties rather than certain definite chemical elements or compounds. Suppose he wants to have a cloak dyed purple. It is a matter of extreme unimportance to him whether the dye came from the animal, vegetable, or mineral kingdom so long as it has certain qualities that are necessary, and it is just as unimportant whether the dyestuff was obtained in the waters off the Syrian coast, in the lands along the Ganges, or in a factory in Hoboken. Two hundred years ago if one wanted heat he burned wood, and economists looked over the wood supply of the world with anxious eyes and wondered what would become of man when the wood supply was gone. If man were as dependent on wood for heat today as he was then it is obvious that our civilization would present a n entirely different aspect, but the answer is that he is not so dependent. Wood is as unimportant for heat as the stearin candle is for light, or as post horses are for transportation. The raw materials that seem to us of such extreme importance today become quite insignificant in the next generation or two. The real service of the chemist lies in the fact that he is freeing or rendering us more and more independent of any specific raw material to supply any specific want. One of the great sources of difficulty between nations in the past has been the urge of some one nation to possess land because that land contained a specific raw material, and that specific raw material was absolutely necessary to supply some need of the world. The farther the chemist progresses in his work the more fully will this source of friction be removed.
Cellulose Sausage Casings’ By William F. Henderson and Harold E. Dietrich MELLON INSTITUTE OF INDUSTRIAL RSSSARCH, UNIVERSITY OF PITTSBURGH, PITTSBURGH, PA.
Introduction February 8, 1916,
The Food Container Fellowship of Mellon Institute, which concluded its research early this year, after almost ten years of continuous operation, had for its the first of the Erwin Freund Fellowobject the devising of an edible, synthetic substitute for the animal casings which have been used almost ships WHs e s t a b l i s h e d a t ~ ~I n s t i t ul t e . Itl was ~ exclusively ~ by meat Packers for many Years. As a result called the Food container of the experimental work Of this fellowship, a product Fellowship and its purpose is’ now available that is ,completely standardized in was to develop a synthetic length and width, is unquestionably satisfactory from casing %.hi& could be used the sanitary and hygienic standpoints, and is moderate In price’ in the manufacture of sau-
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sages a n d wieners. The incumbent of this first fellowship was C. L. Weirich, who investigated the field of materials and processes. On October 16, 1917, the work was undertaken by Frank W. Stockton, who continued it until March, 1920. At this time it seemed fairly certain that the best material available was cellulose. All the well-known methods of manipulating cellulose were also studied, including the nitrate, acetate, cuprammonium, and viscose processes. Of all these procedures, the viscose process was found to be the most suitable. The senior author succeeded Mr. Stockton, and for the next two sears gave special research attention to the chemical phases of the problem. At the end of this time, short lengths of seamless tubes were being produced. The junior author then joined the investigation and the fellowship was placed I
Received August 20. 1926.
on a multiple basis, From this time on, intensive work on the chemical part of the problem was continued and, in addition, the mechanical features of the process were investigated.
The activities of the fell o w s h i p were c a r r i e d on w i t h o u t interruption January, 1926, shortly before which a product had been produced which passed the requirements and conditions imposed by the packing industry. Before the termination of the fellowship, a continuous process for producing the casings had been evolved and the work had been carried on a t Mellon Institute on a unit-plant scale for about two years. All the developments of this research are now being given attention by the Visking Corporation of Chicago, and a factory is under construction for the manufacture of the new product. The Need of a New Casing
At the present time practically all linked sausages are prepared in casings which are made from the small intestines of sheep and hogs. The intestines must be cleaned and the fat, scraped off-an operation which, in the case of sheep
November, 1926
INDUSTRIAL ANI1 EAr@INEEIUNG CIIBMIIs1’RY
casings, is performed almost entirely by hand. Hog casings are thicker and tougher, and for this reason can be clcaned and scraped by specially devised machinery. In both cases the cleaning is preceded by a period of soaking in warm water, which induces putrefaction in the contents of the intestines, thus facilitating their removal. SHEEP CASINGS-Most of the sheep casings used in the sausage industry are imported from China, Russia, the Levant, New Zealand, Australia, some from Western Europe, and some from South America. The cleaning and scraping are done more or Icss completely prior to shipment, and the casings are packed in loose salt or brine and shipped to this country in a great variety of packages, some of them very primitive-as, for example, in goat skins. On arrival they are unpacked, soaked, and graded. Sheep casings are graded according to their diameter into a t least three classes, called wides, mediums, and narrows. The wides must be a t least 7/s inch in diameter; the mediums are from 7/8 to ‘/S inch; and the narrows are less than 6/s inch in diameter. The grading is usually done by expanding the casings with water and gaging them hetween pegs. The ea&@ are then measured int,o skeins or hanks, the length of which varies with the grade, and subsequently they are salted and packed in ticrces, each of which contains about 500 hanks. Sausages made in wide sheep casings appeal most to tlle fancy of the consuming public; hence this grade is the most desirahle and brings the best price. The mediums bring a lower price, and the narrows, being the least desirable, are the cheapest grade. The skeins contain a number of strands of casing, but this again varies with the grade of casing. An ideal skein of the best wide sheep casing contains six strands, each 50 feet in length, but these are very rare. Usually the number of strands is greater and the average length of each strand is Iess. WOO CnsINGtiHog casings are graded in much the same manner as sheep casings, but arc larger than sheep casings, and therefore narrow hog casings, which are only slightly larger than wide sheep casings, are the most valuable. The usual grading is &s follows: narrows, under ll/s inches; mediums, l’/s to 1”s inches; wides, 1”s inches and over. Hog casings are also thicker than sheep casings, and for this reason they are used for the ordinary pork sausage and for the large size wieners. The hog casings used in the United States are prepared largely from native hogs, although in recent years considerable quantities have been imported from China, where the production consists of narrower but much tougher casings. Sausages with excessively tough and “unchewahle” casings are made with Chinese hog casings. ~ I M A LC.4SINQS UNSATISFACTORY-Until the advent of the cellulose casing described in this paper, no suitable synthetic casing had ever been devised which could satisfactorily replace animal intestines, in spite of the fact that, oven with the greatest care, cleaners and grader8 of natural casings were unable to turn out a really clcm or uniformly calihrated article or one which would be of long lengths, free from holes, weak spots, deterioration, or other defects.
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satisfactory was a high-grade type of purified cotton linters. A broad investigation of this material was madeZ and s method developed whereby the cotton linters could be reedity formed into seamless tubes with very thin walls. In order to accomplish this result, it was neccssary to convert the cellulose into some fluid or plastic condition from which it could be readily converted back to pure cellulose. The viscose process was found to he the simplest and to offer the best possibilities, and accordingly it was chosen for fabricating the tubes from cellulose. THEVISCOSEPRocEss-In the viscose process, the cellulose is treated with a 20 per cent sodium hydroxide solution until it is all thoroughly swelled, or mercerized. The cxocss of alkali is then pressed out and the resulting press-cake shredded. The shredded alkali-ccllulo8e is placed in suitable containers and exposed to the fumes of carbon disulfide. The disulfide reacts with the alkali-cellulose and forms a
A Du lex ExPusIon Machine Showing Redpltanng Barbs. feeeeneranng Baths, Wash Tubs. and Winding Device
bright orange product, called ceUulose dithiocarhonate, which is soluble in water or dilute alkali solution and forms the well-known sirupy product, viscose. One of the most characteristic properties of viscose is its instability; from the time it is prepared it begins to hydrolyze slowly, the rate of hydrolysis depending on the t e m p erature. The addition of sodium liydroxidc to viscose retards the hydrolysis hut does not prevent it. This hydrolysis consists mainly in the splitting off of the dithiocarbonate groups and proceeds until the residue has the same composition as cellulose, namely, CsH,aOs. The process is known as the ripening of tbe viscose and is acconrpanied by an increase in viscosity of the material. The viscosity increases until t,he material becomes solid, after which syneresis occurs, the gel shrinking symmetrically until only a small mass of hard, britt,lc ccllulose remains in the watery liquid. Mineral acids react with viscose quickly, yielding cellulose; but in order to produce tho cellulose in the form of a continuous film, the viscose must be allowed to ripen for a time, the lengt,h of which depends on t,lre temperature a t Chemical Research which it is stored. At 10’ C., the viscose is ready to use, RAW1LInTmtp~r.s-The first problem which engaged the after ripening for eight days. Se\wal years were spent in a careful study of the viscose attention of the students in this field was that of a suit.able raw material. Since the film-forming material sought reaction, in order to develop a process by which a film could must be edible, the list of available Fubstances NRS brief. be produced which would be suililble fix use a8 a sausage The groups of materials investigated are included under the casing. Comparatively small variations in the grades of purified cott,on linters produced large variations in t.he following heads: gelatin; casein plastics; carbohydratesquality of the resulting viscose, and it was therefore nccesagar agar, algin, etc., starches, and cellulose. A careful study of these substances led to the choice of a sary to investigate thoroughly these grades of linters 3 Txis J o u a m ~16, , SI9 (1923;. particular type of cellulose. The material found most
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before tile most suitable grade was found. The variations in viscosity were enormous, ranging from 25 to over 6000 seconds in the grades studied. The viscosity determinations were made by t.he falling-ball method rccornmended by the Committee on Viscosity, Celldose Division, AMXRICAN CHEMI~AL S o c i ~ i the ~ , ~temperature used being 0" C., instead of 25O C., as suggested by this committee. MonrmcnnoNs IN 131 -Variations in the prmess f viscose from a singlc grade employed for the producti of cellulose were found to cuusc wide variations in the product,. For example, tlie conccntration of the sodium hydroxide solution used for niercerizat.ion has a pronounced effect on the viscosity of the viscose.' The tempcraturc ani1 lcngtli of time employed in mercerization also exert un important effect. If the aU
