February, 1928
INDUSTRIAL AND ENGINEERING CHEMISTRY
matter will be reduced to 50 grams but the nitrogen in the remaining volatile matter will be 8.0 per cent. CARBONTRANSFORMATION-The reduction of carbon in the unlimed material parallels the reduction of volatile matter. I n both cases the reduction is lower with unlimed than with the limed material. The addition of lime stimulates the decomposition of organic matter, especially the carbonaceous constituents. The most rapid reduction in the carbon content takes place in the later stages of decomposition. The decomposition of cellulose, which takes place in the early stages of digestion, is not accompanied by a material reduction in the carbon content because. in the first place, cellulose constitutes only 5 to 10 per cent of the dry material of the fresh solids, and second, the decomposition products of cellulose, the organic acids, are broken down in the later stages of digestion. Undoubtedly, the decomposition of some carbonaceous substance besides cellulose is the cause of this rapid decrease in the carbon content. It is suggested that the addition of lime accelerates the decomposition of fats, thus causing a great reduction of carbon and volatile matter. Decomposition of fats takes place only in the later stages of digestion. I n the case of unlimed material a 25 per cent reduction of volatile matter was accompanied by only 5 per cent
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reduction of carbon, while in the limed material a 60 per cent reduction of volatile matter was accompanied by a 30 per cent reduction in the carbon content. It would therefore appear that not only does the addition of lime cause a greater reduction of volatile matter, but also a greater proportion of this volatile matter is gasified, whereas in the unlimed material a greater proportion of the decomposed material is left in intermediate forms-that is, liquefied. Thus, it would seem that the addition of lime not only brings into the range of decomposition a greater proportion of substances, but also causes the decomposition of these substances to give greater volumes of gas. Lime causes a more rapid and also a more complete decomposition of the substances that would either decompose partially or not at all. The increase in the carbon content of the volatile matter is not an actual increase, but only an apparent one due to the reduction of the volatile matter. When this is remembered the percentage content of carbon is seen to be actually decreasing in the limed material. On the other hand, the volatile matter of the sludge obtained a t the end of the decomposition has a higher percentage of carbon. The explanation is obvious since the process of humification is one of enrichment of carbon; the higher the degree of humification the greater the percentage of carbon.
Effect of Addition of Salts on the Germicidal Efficiency of Sodium Hydroxide' Max Levine, J. H. Toulouse, and J. H. Buchanan DEPARTMENTS OF CHEMISTRY AND BACTERIOLOGY, IOWA STATECOLLEGE, AMES,IA. Concentration of Added Salts on Killing T i m e of N A previous paper2 it was shown that with the same Table I-Effect of0.5 N Sodium Hydroxide at 50° C. sodium hydroxide concentration the addition of sodium KILLING TIME99.9 PER CENT OF EXPOSED BACTERIA NaCl NazCOa ADDEDSALT carbonate increased the efficiency of the germicidal P H cent Minutes Minutes action of the solution. In this paper are given the results 0 41.0 41.0 of adding salts, with particular reference to sodium chloride. 1 33.8 34.4 2 2 9.9 2 9 . 9 The details of preparation of the culture and technic of 3 25.5 25.2 disinfection were identical with that previously de~cribed.~ The time required to effect a reduction of 99.9 per cent of It will be observed from Table I that the addition of sodium the exposed bacteria was employed as a basis for comparison. chloride or sodium carbonate decreased the killing time Preliminary experiments showed the following: of sodium hydroxide and that the decrease was proportional (1) 1.16 per cent NaCl, 1.5 per cent KCl, and 1.07 per cent to the quantities of added salts. Sodium chloride and sodium NazCOa decreased the killing time of 0.5 N NaOH at 50" C. carbonate were equally effective in this respect. The when the salts were added to the alkali. killing time was effectively reduced 16.8, 27.00, and 38.3 (2). .NaCl, KCl, Na~C03,and Na3P04.12H10 were only weakly germicidal for the test organisms, showing reduction of less than per cent by the addition of 1.0, 2.0, and 3.0 per cent of the salts, respectively. There was no significant change in the 30 per cent in 1 hour at 60" C. H-ion concentration due to the addition of these salts. Experimental
I
Concentration of Added Salts on Killing T i m e of EXPERIMENTS AT 50" C.-To 100 cc. of 0.5 N sodium Table 11-Effect of 0.25 N S o d i u m Hydroxide at 60° C. hydroxide in a three-necked Woulfe bottle was added the R l L L I N G TIME99.9 PER CENT O F EXPOSED BACTERIA ADDEDSALT NaCl NazCOs NasP0~.12HzO desired amount of sodium chloride or carbonate (dry salt). Per cent Minutes Minutes Minutes The mixture was sterilized in the autoclave a t 15 pounds (1 0 42.5 42.5 42.5 atmosphere) for 20 minutes. After cooling, the contents of 1 30.6 29.0 34.9 2 23.4 21.9 28.1 the bottle were brought to the desired temperature in a 3 19.9 20.1 24.7 water bath, inoculated with the test organism, and the surviving bacteria determined as previously described. EXPERIMEKTS a t 60" C.-Owing to the greater sterilThe results are summarized in Table I. izing effect a t 60" C., a sodium hydroxide solution 0.25 N Figures 1 and 2 show curves obtained by plotting logarithms was used in place of the 0.5 N solution employed at 50" C. of the average per cent surviving bacteria against time. Sodium chloride, sodium carbonate, and trisodium phosphate Received September 17, 1927. This study was made possible through were the salts used, in strengths of 1.0, 2.0, and 3.0 per cent, a fellowship maintained by the American Bottlers of Carbonated Beverages respectively. The increased sterilizing efficiency of the at Iowa State College. sodium hydroxide with the addition of these salts is given * I n d . Eng. Chcm., 20, 63 (1928). * Iowa State College J . Science, 1, No. 4, 379 (1927). in Table I1 and in Figures 3, 4, and 5. f
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 20, No. 2
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Here again it is evident that all three salts distinctly decreased the killing times. The influence of the sodium chloride and sodium carbonate was approximately the same while the phosphate was less efficient. Thus with the addition of 1.0 per cent of the salts a reduction of 28, 30, and 17 per cent, respectively, was obtained in the time required to effect a reduction of 99.9 per cent of the exposed bacteria. These observations were made on the basis of equal quantities, by weight, of the salts. If equivalent quantities of chloride, carbonate, and phosphate had been added on the basis of the sodium ion, the phosphate would have been more effective with respect to a reduction in the killing time. Discussion
No adequate explanation of the influence of the added It is conceivable that the un-
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40
dissociated sodium hydroxide rather than the OH ion may be the agent which penetrates the bacterial cell, thereby causing death of the organism. Addition of the various salts employed would tend to decrease the dissociation of sodium hydroxide and thus increase the concentration of undissociated sodium hydroxide, resulting in an increased germicidal efficiency. Another explanation is that the added salts would decrease the solubility of the sodium hydroxide in the water phase of the bacterial suspension, and as a consequence the sodium hydroxide would be forced into the bacterial phase. Work is in progress a t the present time to determine this point. The results shown in Figure 6 enable one to calculate the relative effects of addition of sodium chloride, sodium carbonate, and sodium phosphate to a solution of sodium hydroxide, on the germicidal efficiency of the NaOH.
ISDC‘STRI.4 L A N D ENGINEERING CHEMISTRY
February, 1928
Summary
The addition of sodium chloride, sodium carbonate, or trisodium phosphate to sodium hydroxide markedly decreases the killing time a t 50” and 60” C. The effects of equal weights of sodium chloride and sodium carbonate are approximately the same, whereas the trisodium phosphate is less efficient. As the concentration of salts added to the sodium hy-
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droxide is increased the killing time is decreased, but at a decreasing rate. It is suggested that the undissociated sodium hydroxide may be the agent which penetrates the cell. The addition of the various salts would increase the concentration of undissociated sodium hydroxide, or possibly decrease the solubility of the sodium hydroxide in the water phase which would tend to force the sodium hydroxide into the bacterial phase of the suspension. In either case the effect would be to increase the death rate of the bacteria.
Some Preliminary Experiments on Fat-Liquoring’ Henry B. Merrill A. F. GALLUN & SONSCo.,MILWAUKEE, Wis.
T SOME stage between tanning and finishing all leather undergoes a treatment designed to incorporate in the tanned skin a certain amount of oil. Light leathers are generally drummed with an emulsion of various animal or vegetable oils, the process being known as “fatliquoring.’’ If the operation is properly carried out, nearly all the oil in the fat-liquor is absorbed by the skins, the used liquor is nearly clear, and the skins themselves neither look nor feel greasy, in spite of containing up to 20 per cent of fats and oils. Almost no quantitative work has been done on the chemistry of fat-liquoring. Except that it has been recognized that a fat-liquor must be a fairly stable emulsion, almost nothing is known of the nature of the interaction of oil and leather, and of the variables which affect it. Most of the fatliquors in use are quite complex, containing numerous constituents in proportions which are juggled until a desired effect is obtained, after which the formula thus obtained is adhered to rigidly. Preliminary to any attempt to determine the function and laws governing the employment of the various constituents of practical fat-liquors, it is necessary to study in
A
Experimental Procedure
The fat-liquors employed contained nothing but water and a sulfonated neat’s-foot oil (H,O, 22.3; ash, 4.7; total oil, 73.0; SOa combined with oil, 3.4 per cent), plus borax or sodium carbonate to regulate the pH value. The leather employed was ordinary 1-bath chrome calf, taken after coloring but before fat-liquoring. Small strips of this leather were fat-liquored under controlled conditions and, after drying, were split into five layers on a skiving machine. Each split was analyzed for fat, and from the thickness of the several splits and their fat content the penetration of the oil into the skin was shown, as well as the total amount of oil taken up by the leather as a whole. The exact composition of the liquors and the time of fat-liquoring are given in connection with the figures. I n all cases the temperature was 40” C. a t the outset, and fell off but little during the course of the experiment. I n expressing the results obtained for distribution of oil in the skin, the percentage of fat (dry basis) in each layer was plotted as a function of the depth of the center of that layer below the grain surface in percentage of the total thickness of the skin.
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Fat-liquor: 2.5 grams sulfonated neat’s-foot oil; 0.25 gram borax in 50 cc. per 100 grams wet leather. Time: 2 hours
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hv. depth 2b belowrbmain : Pl‘ELnt 6b
Fat-liquor: sulfonated neat’s-foot oil and borax (10:l) in 50 cc. volume per 100 grams leather, Time: 2 hours
the simplest possible system the effect of such fundamental variables as ratio of oil to leather, concentration, time, and p H value upon the total quantity of oil absorbed and its & tribution in the leather. The results of such experiments me reported in this paper. 1 Pesented under the title “A Preliminary Study of Fat-Liquoring” before the Division of Leather and Gelatin Chemistry at the 74th Meeting of the American Chemical Society, Detroit, Mich., September 6 to IO, 1927.
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Fat-liquor: sulfonated neat’s-foot oil and borax (1O:l) in 50 cc. volume per 100 grams leather. Time: 2 hours.
Distribution of Oil-Effect
of Drying
h d be seen from Figure 1, the distribution of fat in Chrome leather is far from Uniform. The center contains no oil except the natural skin fat. Contrary to a widespread impression, penetration of the oil does not take place chiefly through the flesh side; if anything, more Oil is absorbed through the grain. No change occurs in the distribution of
