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The heating chamber of this apparatus was essentially the same as that in Figure 1 4 . e., a vertical inner tube to receive the sample, this tube immersed in a lead bath, and the bath heated in an electric furnace. As in determining the softening point, nitrogen was passed down through the steel coil and up through the inner tube containing the coal sample. At the bottom of the inner tube was placed a short solid cylinder of steel, somewhat smaller in diameter than the inner tube, with a flat-bottom well a t its upper end. The coal to be tested was made into a briquet and placed in the well. On the briquet rested a steel rod which passed up through guides and carried a platform for weights a t its upper end. I n order not to place too much weight on the electric furnace, the inner tube was supported independently of the furnace as indicated in Figure 6. Table 111-Plasticity
of Coal at Temperatures below the Softening Point
COAL
TIME ROD NO. TEMP.ELAPSED SETTLED a C. Min. Mm.
10
412
60
18
10 10 2
405 395 385
110 251 25
3 4 23
2
348
95
0
REMARKS
N o further settling after 1 hour, briquet deformed Briquet barrel-shaped at end of run
Briquet had flowed up around rod, the coal quite plastic Briquet distorted
I n making a run the lead bath was brought up to the desired temperature and the nitrogen stream started through the apparatus. The briquet was then lowered into place, the rod brought down upon it, and weights amounting to 25 pounds (11.35 kg.) placed on the platform. The rod and platform weighed 1 pound (0.45 kg.), so that the load on the briquet was 26 pounds (11.80 kg.) or nearly 340 pounds per square inch (24 kg. per sq. cm.). As soon as steady conditions were established a t the predetermined constant temperature, the position of a mark on the vertical rod was observed
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with a cathetometer. Plasticity in the briquet w&s indicated by a slow settling of the vertical rod and the briquet was examined for deformation a t the end of the run. The results obtained with this apparatus are summarized in Table 111. It will be noted that both these coals exhibited plasticity at temperatures as much as 35 degrees below their softening points as determined by the gas-flow method, and that S o . 2 coal is more plastic near its softening point than is No. 10 coal. There is probably a relationship between the degree of plasticity exhibited below the softening point and the degree of fluidity reached after the coal passes the softening point; and the difference in plasticity exhibited a t temperatures below the softening points may be one of the factors which cause wide variation in the ease with which different coals can be briquetted. Plasticity of the sort exhibited by bituminous coals is characteristic of amorphous substances such as glass. Some investigators claim that coal and coke give x-ray diffraction patterns. This argument has been considerably weakened by a recent observation that the ash of a particular anthracite coal gave the same pattern as the coal itself. During the course of the present investigation x-ray photographs were made of No. 10 coal and of its semi-coke, using powdered samples. No diffraction patterns were discernible in either case. Coal No. 10 is so low in ash that interference from this source disappears. Literature Cited (1) Audibert, Fuels Science Praclice, 6, 229 (1926). (2) Coffman and Layng, IND.ENG CHEM.,20, 165 (192s). (1924). (3) Foxwell, Fuels Science Practice, 3, 122,174,206,227,276,316,371 (4) Layng and Coffman, IND.ENG.CHEM.,19,924 (1927). ( 5 ) Layng and Hathorne, I b i d . , 17, 165 (1925). (6) Parr and Olin, University of Illinois Eng. Expt. Sta., Bull. 60 (1912). (7) Porter and Ralston, Bur. Mines, Tech. Paper 66 (1914).
Carbon Dioxide Preservation of Meat and Fish' D. H. Killeffer DRYICE CORPORATION OF AMERICA, 52 VANDERBILT AVE., NEW YORK,N. Y.
Carbon dioxide atmospheres have long been known preserved meat and fish better to exercise a preservative action on certain food prodt h a n o t h e r perishable prodpreliminary character ucts. This paper describes the results of a preliminary ucts. M a n y s t a t e m e n t s , and do not by any study of the effect of carbon dioxide on meat and fish b a s e d f r e q u e n t l y on very means exhaust the subject. and on certain common bacteria. It is shown that s c a n t evidence, have been C o n s i d e r a b l e temerity in meat and fish can be kept fresh longer when refrigerated made regarding the efficiency d r a w i n g conclusions from in a carbon dioxide atmosphere than in air, that carof c a r b o n dioxide atmossuch scanty observations is bon dioxide is absorbed by meat and fish as indicated pheres in preventing spoilage freely admitted, particularly by pH changes, and that the growth of common bacof foods. Long ago patents since the bacterial studies do teria studied is greatly impeded, if not actually stopped, were issued on preservation of not include many of the types by the presence of dissolved carbon dioxide in the foodstuffs by carbon dioxide of bacteria common to meat culture medium. Further work on the subject is atmospheres. Many of them a n d f i s h . Xevertheless, in desirable on account of the increasing importance have proved disappointing on view of the obvious imporof solid carbon dioxide (Dry-Ice) as a commercial recareful i n v e s t i g a t i o n , but tance to the meat industry of frigerant. nevertheless in the particular t h e f i n d i n g s , it has been case of flesh foods really rethought wise to publish this preliminary discussion a t this time for criticism and suggestion. markable results have been obtained. It is the purpose of I n attempting to explain some of the facts of Dry-Ice refrig- this paper to describe some investigations of this preservaeration, it early became obvious that mere refrigerating effect tive effect of carbon dioxide atmospheres and to point out alone could not cover the entire situation as it was observed, a hitherto neglected field for further research and applicaespecially with respect to meat and fish. Strangely enough, tion to the meat industries. identical refrigerating systems using Dry-Ice as the refrigerant Effect of Carbon Dioxide Gas on Meat
T
HESE studies are of a
1 Received December 5, 1929. Presented before the Scientific Section of the Convention of the Institute of American Meat Packers, Chicago, Ill., October 18, 1929.
I
Questions arose early in the commercial application of solid carbon dioxide refrigeration, as to whether the gas itself had
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ISDCSTRIB L A S D E-YGINEERISG CHEXISTRY
any deleterious effect upon ineat stored in it. To answer this, a number of commercial samples of beef, pork, poultry, butter, eggs, and cheese were suspended in individual tin cans of sufficient size to prevent contact with the cans and to insure complete coverage of the samples by the atmosphere surrounding them. List of Samples Exposed Round steak 3 pounds Duck ( 2 ) Pork sausages Soup meat I O3/r pounds Frankfurters h-eck bones 3 pounds Butter Sweetbreads 2 pair 2 Cheese (Snappy, Kraft, Beef kidneys Roquefort, Camembert) Spare ribs 3 pounds Eggs Pork trimmings 4 pounds Lamb chops Pork loins 6 pounds Bought from a retail butcher in New York City.
pounds 2 pounds 2 pounds 2 pounds
Ql/4
2 pounds 2 dozen 3 pounds
One set of cans was connected to a sourceof a slow, continuous supply of gaseous carbon dioxide, and a duplicate set closed with air in the cans and sealed to prevent the accidental contamination of the air by carbon dioxide. Both sets of cans, containing duplicate qamples and cut where possible from the same pieces of meat, were placed in a refrigerator side by side a t 40" to 45" F. The flow of carbon dioxide through the carbon dioxide cans connected in parallel was at an average rate of 3 to 4 cubic feet per hour distributed through twelve cans, or an average of' 0.25 to 0.30 cubic foot per can per hour. The purpose of this was to insure that any deleterious effect of the gas would not be nullified by leakage of carbon dioxide out and air into the cans. The gas supply was passed through 15 feet of rubber tubing within the refrigerator before reaching the cans to bring it to the refrigerator temperature and prevent either cooling or warming of the carbon dioxide cans to a different temperature from the others. The samples were inspected at frequent intervals and a t the end of 2 weeks a difference had developed worthy of note. These interim inspections were made only of one, or a t most two cans in each set t o determine approximately what might be expected of the entire sets. At the end of 2 weeks the inspector from a nearby meat company was called in to inspect all samples. He unhesitatingly discarded as spoiled the airstored samples of pork spare ribs, soup meat, lamb chops (10 days only), kidneys, sweetbreads, frankfurters, and pork sausage. All of the COrstored samples were in good condition and did not begin to show spoilage until the end of the third week. At that time the spoilage of air-stored samples of meats was complete. Butter, cheese, and eggs in both air and carbon dioxide were still in excellent condition. Rough though it was, this test indicated a definite preservative action of carbon dioxide atmospheres. Two possible explanations offer themselves. Bacterial growth might be materially reduced by the absence of oxygen in the atmosphere around the meat or a condition might be set up on the actual surface of the meat unfayorable to f he bacteria. It seems probable that both factors are of importance. Degree of Preservative Action
Later, inore careful tests were made with the idea of determining more definitely how potent this preserbative action is. It was found that samples of both meat and fish, when placed in atmospherrs of substantially pure carbon dioxide, would keep twice to three times as long as when in air a t the same temperatures. It was even found to be feasible to store meat and fish for several days a t a temperature as high as 80" F. in carbon dioxide. To follow the changes in the meat in B manner which would be fairly accuratcb and a t the same time not too complicated for continual use with many samples, a colorimetric p H method was employed as offering a ready means of following the absorption and evolution of carbon dioxide by samples exposed to it. Chlorophenol red with a blue light filter was used as the most convenient indi-
141
cator. By observing the condition of the samples and determining their pH value changes during storage a fair idea was gained of the effect of carbon dioxide and the extent of its absorption. The charts of results of these studies show quite clearly (1) that carbon dioxide is absorbed by meat and fish; (2) that p H values proT-ide a t least an approximate method of following the changes thus produced; (3) that meat and fish are preserved even at relatively high temperatures by the absorption of gas; (4) that after a short period of exposure no further effect is detectable in the meat or fish; and (5) that in no case did the fall of the pH value as determined on the exposed meat even approach that of beef extract completely carbonated.
EXPOSUREOFSOUPMEAT TO 100%COz 68 661
i'i TIME INHOURS
-
Change of pH Value of Beef Muscle during Exposure to COZAtmospheres
Several peculiarities are apparent from the accompanying charts, which are representative of a great many tests. Although the samples of meat were obtained from the same retail store and were presumably the same in every case, the wide variation of original pH values indicates distinct differences between samples. Apparently these differences were the result of the previous history of the meat and may very well have been caused by bacterial action. In every case the meat samples used showed a slightly slower p H value than that of freshly killed beef muscle, which is in general around 6.4. Every sample of meat showed a lowered pH value after exposure to carbon dioxide a t temperatures above freezing. One sample held in high concentration carbon dioxide in a solidly frozen condition (0" to 10" F.) did not change. All samples removed from carbon dioxide to air showed a rising pH value. It seems reasonable to presume from these observations that the absorption is almost, if not wholly, a physical phenomenon, involving no more tightly bound chemical compounds than carbonic acid. The probability is that carbon dioxide is merely dissolved in the juices of the meat, from which it is easily evolved on exposure to air or slight warming, or both. Cooked meats (cold cuts) stored for as long as 10 days in carbon dioxide both before and after cooking possess no detectable off-flavor from the treatment.
IKDUSTRIAL A N D ENGIXEERING CHEMISTRY
142
The relatively slight drop in pH value observed in all of these tests as compared with the drop obtained by carbonation of extract of fresh beef (6.4 to 5.5) is probably due to the relatively thin surface layer of the meat affected by the gas. I n taking samples for pH value, thin slices were cut from exposed samples of a pound or so of meat to give a fairly representative proportion of surface to center of piece in each case. The presence of relatively large proportions of the unexposed and presumably unaffected core of a piece in the pH test samples would naturally yield a high p H value on account of the buffer action of the unchanged core. The behavior of fish is similar to that of meat, although the absorption of carbon dioxide as indicated by the pH value is somewhat greater and its preservative effect somewhat more pronounced. Effect of C a r b o n Dioxide o n Bacterial Growth
I n addition to the p H studies and storage tests made upon meat and fish, a series of bacteriological tests has been made to determine the effect of carbon dioxide on bacterial growth. Because of the virtual impossibility of making qualitative and quantitative cultures on either meat or fish, it was decided to carry on these experiments using nutrient agar plates, exposing duplicate plates to carbon dioxide and air.
EXPOSUREOF COD FISHTO 100 co,
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summer, 1929) for the intervals indicated and a t the end of the time the number of colonies on each plate was counted. Tabulation of Bacterial Counts COLONIES IN: TIME Air COS AIR AFTER CO? Days Staphylococcus aureus 2 1960 None . .. .. Micrococcus ovalis 2 1945 350 (7 days) (”) Innumerable Micrococcus catarrhalis 2 Innumerable 14’ hTone Streptococcus viridans 2 2355 175 (7%) 299 (7 .. days) Streptococcus non-hemolyticus 2 75 None None Proteus vulgaris 50 Sone . .. Proteus vulgaris 4040 126 (3%) 164 (2 days) Bacillus coli 1 92 0 0 (7 days) Bacillus coli 5 710 3; ( 5 % ) 719 (2 days) Bacillus typhosus 1 615 . .. , . .. . Bacillus typhosus 5 274 304 .. . , . . . . Bacillus typhosus 5 120 119 (100%) .. . . . , . . Feces, fresh 2 12311 6789 ( 5 5 % ) . . .. . . . . Urine, decomposing 2 2375 1060 (45%) 1515 (2 days) ORGANISM
.. .
5
.. . . I
With the exception of B. typhosus, all cultures showed a reduction in the number of colonies grown in carbon dioxide as compared with air. This exception does not exist during a short (1-day) culture period, but becomes evident later. It seems obvious from this that the growth of the bacteria is very much slower in carbon dioxide than in air and that the longer periods allow the colonies to grow to visible size. If it were practical to count the individuals in each colony, it seeniq highly probable that the air colonies would each show a much greater number of bacteria than the carbon dioxide colonies. In other words, the carbon dioxide atmosphere does not render these bacteria dormant, but does greatly retard their growth. Apparently the situation with respect to carbon dioxide and its effect on meat and fish is due very largely to the change in pH value of the nutrient medium. I n some of the culture plates this change was sufficient to kill the bacteria outright. I n others, the bacteria were merely prevented from growing. It is especially interesting to note that the effect on cultures has not been simply to restrain the growth of aerobic bacteria and permit the free growth of anaerobes, as one might expect to be the normal outcome of replacing air by another gas. Much work on the effect of pH changes of media on the growth of bacteria has been published by bacteriologists of the U. S. Department of Agriculture and others. Even the bibliography of the subject is too voluminous for inclusion here. Indeed, it has been frequently demonstrated that changes in the p H value of the nutrient medium, even though relatively slight, have a profound influence on growth of many kinds of bacteria. Application t o T r a n s p o r t a t i o n of M e a t a n d Fish
I
TIME IN HOUR5
-
I
Change of pH Value of Cod Fish Steak during Exposure to COZAtmospheres
Preliminary tests with standard nutrient agar plates made alkaline by the addition of sodium hydroxide solution showed complete penetration of carbon dioxide as indicated by methyl red, bromocresol purple, thymol blue, and phenolphthalein. S o t only was the indicator color changed to the acid side by exposure to carbon dioxide, but it returned to the alkaline side by subsequent exposure to air. The procedure adopted with bacteria follows: Standard nutrient agar was seeded with the particular organism from a 24-hour growth in nutrient bouillon and two 10-cc. portions were poured into Petri dishes forming a layer about 4 mm. deep. One plate was then exposed (open) to an atmosphere of carbon dioxide in a glass vessel and the other (covered) to air. All cultures were made a t room temperature (New York,
I n applying these observations to the safe transportation of meats and fish with Dry-Ice refrigeration, the requirements of the ideal modus operand2 seem to be fairly definite: First, the commodity should be kept a t a proper temperature in transit. The effect of carbon dioxide gas properly applied is to allow safe transportation for a limited period a t higher temperatures than would be required without it. It is even possible that proper application of the gas treatment would permit safe transportation of meat and fish during most of the year without refrigeration. The hitch, as yet, lies in the “proper application” under conditions feasible in commercial practice, and since there is a hitch our safest reliance is low temperature with gas preservation as a safeguard. Second, the commodity should be allowed to absorb as much carbon dioxide as possible. This can be accomplished most easily by treating i t with carbon dioxide under alternate pressure and vacuum. This, however, is scarcely practicable. The next best possibility is t o expose it to a high concentration of gas. At least 12 hours’ exposure is necessary for maximum absorption and a longer time would be advantageous. Naturally the meat should be as clean as practicable. Reference is made more particularly to bacterial cleanliness of the meat, for obviously a well-started growth is less easily stopped than an incipient one. Third, during transportation or storage as high a carbon dioxide concentration as practicable should be maintained around the
I S D U S T R I A L AiYD ESGINEERISG CHEMISTRY
February, 1930
143
commodity to prevent the evolution of the absorbed gas. DryIce offers a practicable method of maintaining a controlled supply of carbon dioxide t o a package in transit. I n order not to be wasteful the package must be as nearly gastight (except for a properly placed vent) as possible to minimize the rep1:xement gas required. This is also quite essential from a purely refrigeration point of view, as it avoids the necessity for uselessly cooling great volumes of air, passing through a leaky package. Fourth, as much insulation as practicable must be used to prevent too great temperature fluctuations in thc load with changes of outside temperature.
method or modifications of it during next summer. hIany variables other than those mentioned above have been found to affect the practical utility of a package of meat refrigerated in transit. These are being carefully investigated and evaluated. Humidity, physical condition of the meat, kind of meat, and many other factors are important, and their control must be effected before the ideal result is obtained.
The application of these observations to a safely successful package is progressing rapidly, and it is anticipated that packaged meat and fiph will he handled very largely by this
The bacterial work summarized above was done by E. E. Smith, consulting bacteriologist, and much of the other work was done by A. J. Granata. of this laboratory.
Acknowledgment
Triethanolamine Emulsions‘ A. L. Wilson C A R B I D E A S D C A R B O S CHEMICALS CORPORATION,
HE field of emulsions in modern industry is not only extensive, but exc eedingl y diversified. The variety of problems which are encountered seems t o be equaled only by the variety of t h e i r s o l u t i o n s . I t is therefore interesting to find in triethanolamine a material which is well suited t o a simple and generally applicable met hod of emulsification.
T
EAST
4
2 S T~, XE\V ~
YORK,
As the basic const ituent for soaps, a commercially new product, triethanolamine, seems preeminently adapted for emulsification purposes. Triethanolamine, N(C2H40H)3, iq of which it may be an organic base related to ammonia, ”3, considered a derivatii-e. Like ammonia, it reacts with acid< in molecular proportions to form salts-the hydrochloride, for example, being NH(C2H40H)3C1, showing that only the amine group is alkaline. Triethanolamine differs from animonia, however, in several important properties. It is a high-boiling liquid which is difficultly volatile either alone or in compounds, it is only very mildly alkaline and has no co1rosive action on the skin or on natural fibers, and it is widely soluble in organic liquids. The material that is at present available is a quite uniform mixture of pure triethanolamine with smaller amounts of diethanolamine and monoethanolamine. Since the prdperties of these amines, however, are very similar, the properties of the technical product may be considered as an average of its constituents’ properties and sufficiently invarimt for ordinary formulation. Commercial triethanolamine is a clear, colorless to straw-colored liquid, viscous and 1.ei-y hygroscopic. The specific gravity a t 20” C. is 1.124, and the boiling point a t I50 mm. pressure is 277” C., decomposition with a darkening of color taking place a t higher temperatures. It is soluble in most organic liquids containing combined oxygen, such as alcohols, esters, and many ethers, but is only slightly soluble in hydrocarbons. Its dissociation constant is 2.5 X which confirms its very low alkalinity. Stable salts are formed, however, by interaction with most acids, although the salt of such a weak acid as abietic is almost completely
Y. 1’.
hydrolyzed in water solution. In this reaction the combini n g w e i g h t is equal to the average molecular weight and has a value of 127, approximately. T h e f a t t y acid soaps of triethanolamine exhibit unique characteristics. The oleate is the most familiar and amears to be the most rrenera l l y useful of these-compounds. It is formed by interaction of the anhydrous base with oleic acid, or “red oil,” in the proportions given by their equivalent weights. For triethanolamine the value given above is sufficient for the usual purposes, although any possibility of appreciable contamination with moisture makes it advisable to carry out a titration against standard acid using methyl orange as an end-point indicator. The saponification reaction goes to completion a t ordinary temperatures when the materials are stirred together, and is accompanied by the evolution of a small amount of heat. The product is a very &cow soap, one of the characteristics of which, as might be expected, is the non-critical nature of its properties a t the equivalence point; in other words, a slight excess of acid or base above equivalent proportions only slightly changes it. properties, such as viscosity, pH value, or emulsification power. Triethanolamine oleate is completely miscible with practically all organic liquids, including hydrocarbons, with the exception that certain heavy mineral oils and fatty glyccrides may require the addition of excess acid. The water solutions of this soap approach very closely the properties given by a theoretically “neutral soap,” the pH value of a 5 per cent solution having been determined as 7.8. They also exhibit the great value of this soap as a surface-tension depressant, the surface tension of a 0.15 per cent solution at 25’ C. being slightly below 30 dynes per square centimeter. The other liquid soaps of triethanolamine are similarly prepared and possess similar properties. Among these the linoleate is indicated as being exceptionally well suited for emulsification. It will be noticed in Table I that boiled linseed oil, with its natural content of free linoleic acid, requires an unusually small amount of soap for emulsification. The stearate is a hard soap, which is prepared by reaction of the base with the acid a t its melting temperature or by their reaction in a mutual solvent solution. I t is especially
A new commercial material, triethanolamine, is shown to be well suited for emulsification purposes, and to have a number of advantages over the usual inorganic bases used for this purpose. A new method of emulsification with this product, which is applicable to the emulsion of any type of material, is described. The use of triethanolamine as a basic material for soaps, and for the emulsification of soluble mineral oils, vegetable and animal oils, waxes, and various solvents is discussed and illustrates the general utility of triethanolamine in this field.
Triethanolamine and Its Fatty Acid Soaps
Recei\ed November 2 3 . 1929
30
A *
