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loses its toxic properties although it may still contain a small amount of d-gossypol. Although cotton seeds are extremely toxic, they also may be rendered non-toxic by autoclaving in a wet condition. By heating the seeds for a short time in a dry condition the gossypol becomes partially converted to the insoluble form and a separation made of the two by extraction with ether. The insoluble gossypol so produced is much more toxic than the insoluble form found in cottonseed meal or in
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seeds which have been subjected to steam heat. The determination of d-gossypol by the present chemical methods is not a safe criterion for estimating the toxicity of cottonseed products. Acknowledgment The writer's thanks are due to V. G. Heller and N. B. Guerrant for their constant interest, and advice during the progress of this work.
Germicidal Efficiency of Sodium Hydroxide and Sodium Hydroxide-Carbonate Mixtures at the Same H-Ion Concentration'j2 Max Levine, E. E. Peterson, and J. H. Buchanan DEPARTMENTS OF CHEMISTRY A N D BACTERIOLOGY, Iowa STATECOLLEGE, AMES, IA.
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T HAS been suggested that the H-ion concentration might be employed as an index of the germicidal efficiency of alkaline washing solutions. Observations with sodium hydroxide, sodium carbonate, and trisodium phosphate indicated very clearly that the H-ion concentration was not a dependable measure of the relative germicidal efficiencies of theqe alkalies.3 Thus a t p H 12.15 and 70" C:. the killing times for 99.9 per cent of about a million bacterial spores were approximately 5 and 36 minutes for the trisodium phosphate and sodium hydroxide, respectively. Many of the washing compounds consist of sodium hydroxide or mixtures of sodium hydroxide and carbonate. It was the purpose of the following observations t o ascertain whether sodium hydroxide and mixtures of the hydroxide and carbonate a t the same H-ion concentration were equally effective as germicides. The procedure employed was t o determine the surviving bacteria after various periods of exposure to the alkali solution and ascertain the time for effecting a reduction of 99.9 per cent. The organism employed was a spore-former of the Subtilis group. The details as to preparation of the test culture and technic of disinfection were identical with those previously described in studies on the effect of concentration of sodium hydroxide and temperature on disinfection.4 Experimental
At pH 13.20 a 0.48 N sodium hydroxide was only slightly more efficient than a normal alkali mixture consisting of 1.33 per cent sodium hydroxide plus 3.5 per cent sodium carbonate. The hydroxide effected a reduction of 99.9 per cent of the exposed bacteria in 40.9 minutes, as compared with 43.7 minutes for the alkali mixture. At p H 13.32 the sodium hydroxide solution (0.725 N ) was more effective as a germicide than the normal alkali mixture consisting of 2.0 per cent sodium hydroxide and 2.7 per cent sodium carbonate. The killing time for 99.9 per cent of the exposed bacteria a t 50" C. was 22.8 minutes for the hydroxide and 31.1 minutes for the mixture. At p H 13.40 and 50" C. the hydroxide (0.8425 N or 3.4 per cent) effected a reduction of 99.9 per cent in 15 minutes as compared with 18 minutes for the carbonate-hydroxide mixture (2.7 per cent NaOH 1.8 per cent NaEOa).
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The H-ion concentration does not seem to be an accurate index of the relative germicidal efficiencies of solutions of sodium hydroxide as compared with hydroxide carbonate mixtures. SODIG11 HYDROXIDE AKD A COMMERCIAL -4LK.4Ll \vASHIIUG ComrPouxD-A widely used commercial washing compound consisting of a mixture of sodium hydroxide and carbonate JTas employed, the concentration being adjusted t o give a pH of 13.18 for the 50" and 60" C. series. This correqmnded to a 0.5 sodium hydroxide which gave pH 13.20. The concentration of the commercial mashing compound on titration using methyl orange indicator was equivalent to a normal alkali, and contained 1.99 per cent NaOH and 2.66 per cent SODIUM HYDROXIDE AXD SYXTHETIC HYDROXTDE-CARBOSATE MIXTURES-In this series of experiments normal alkali -Ua?C03on a weight basis. solutions were prepared by mixing various quantities of norFigures 3 and 4 show the results obtained a t 50" and mal sodium hydroxide and normal sodium carbonate. The BO" C., respectively. It is apparent that the commercial germicidal efficiencies of these mixtures a t 50" C. were then washing compound a t p H 13.18 was a better sterilizing agent compared with those of sodium hydroxide solutions of the than sodium hydroxide a t approximately the same reaction same H-ion concentration. (pH 13.20). Thus a t 50" C. the killing time of 99.9 per cent of the exposed bacteria was 34 minutes for the commercial T a b l e I-Composition of Alkali S o l u t i o n s SODIUMHYDROXIDE A N D CARBONATE compound as compared with 40.8 minutes for the hydroxide, SODIUMHYDROXIDE MIXTURES while a t 60" C. the killing times were 8.5 and 11.75 minutes, PH SOLUTION h'aOH NazCOa NaOH liaL!Os respectively. A: J '. _b-v z t . Parts Pavts c7, b..v w t . c7, b-v z t- 13.20 0.48 1.92 1 2 1.3 3.5 An analysis of the test materials shows that the commercial 13.32 0.725 2.90 1 1 2.0 2.7 compound in the concentration used contained practically as 13.40 0,843 3.40 2 1 2.7 1.8 much caustic alkali as the pure sodium hydroxide. The reThe composition of the various solutions is indicated in sults therefore indicate that the presence of the carbonate in Table I. The results are shown graphically j.n Figures 1 the commercial product served to increase the germicidal and 2. They may be summed up as follows: effect of the sodium hydroxide present, although the p H was 1 Received June 29, 1927. not appreciably affected. 2 These studies were made possible through a fellowship maintained by Another series of observations on the relative germicidal the American Bottlers of Carbonated Beverages at Iowa State College. efficiency of sodium hydroxide and the commercial washing a Levine, Peterson, and Buchanan, I n d . Eng. Chem., 19, 1338 (1927). 6 Iowa Sfate College J . Science, 1, No. 4, 379-394 (1927). compound described above was carried out a t 70" C. with I-
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2 0
40
/O
i 2
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/O
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commercial compound as compared with pure caustic, and the higher the temperature the greater was the discrepancy between these two determinations. Discussion
weaker concentrations of the alkalies. A 0.25 N sodium hydroxide (1.0 per cent) with a reaction pH 12.99 was compared with a solution of commercial compound at pH 13.0. On a titration basis (methyl orange) the solution of commercial compound was equivalent to 0.5 N alkali and contained 0.995 per cent sodium hydroxide and 1.33 per cent sodium carbonate. The results are indicated in Figure 5 . At 70" C. the commercial washing compound at pH 13.0 effected a reduction of 99.9 per cent of exposed bacteria in 6.3 minutes, as compared with almost 12 minutes required by sodium hydroxide at pH 12.99, The concentration of sodium hydroxide in the two test solutions was practically the same (1.0 per cent), but the commercial compound contained in addition 1.33 per cent sodium carbonate. This additional carbonate did not affect the H-ion concentration of the mixture appreciably, but the germicidal efficiency was markedly increased. The H-ion concentration (expressed a t 30" C.) was not a dependable index of the relative germicidal efficiency of the
At a constant temperature and H-ion concentration (determined a t 30' C.) sodium hydroxide and hydroxide-carbonate mixtures were not equally efficient germicides. Thus it is seen from Table I1 that at pH 13.18 to 13.20 and a temperature of 50" C. the commercial alkali killed in 34 minutes, the sodium hydroxide in 40.8 minutes, and the hydroxidecarbonate mixture in 43.7 minutes-a variation of 22.6 per cent in killing time. The titratable alkalinity was also unsatisfactory as an index of relative disinfecting power, for the 0.5 N hydroxide was less efficient than one of the 1.0 N hydroxide-carbonate mixtures but more efficient than the other. of Composition of Alkalies a t p H 13.18-13.20 to Killing T i m e s at 50° C. ALKALINITY CONCENTRATION KILLINQ SAMPLE B Y TITRATION NaOH NarCOa TIME N Pev cent Per cenf Minutes NaOH 0 5 2.00 0.00 40 8 NaOH-NazC03 mixture 10 1 30 3.50 43 7 Commercial washing powder 1.0 1.99 2.66 34 0
Table 11-Relation
A comparison of the commercial alkali with the 0.5 N sodium hydroxide is extremely interesting. These two solutions contained practically the same quantities of sodium hydroxide (1.99 and 2.00 per cent), but the commercial product had in addition 2.60 per cent of sodium carbonate. The presence of the carbonate did not measurably change the H-ion concentration, but the killing time was reduced from 40.8 minutes to 34.0 minutes. From unpublished available data we can say that the disinfecting action of the sodium carbonate (2.66 per cent) at 50" C. was nil. It is therefore
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believed that the presence of the carbonate enhanced the germicidal efficiency of the hydroxide. If the commercial alkali is compared with the hydroxidecarbonate mixture, it will be noticed that they had the same reaction (pH) and were both normal alkalies by titration, but the killing times were very different-namely, 34.0 and 43.7 minutes, respectively. Evidently neither the total alkalinity nor the H-ion concentration alone is a direct measure of the germicidal powers of these alkalies. Other factors are involved. It is conceivable that the undissociated sodium hydroxide, rather than the OH ion, penetrates the bacterial cell. I n this case the concentration of undissociated sodium hydroxide becomes the determining factor in the germicidal efficiency of alkalies. The addition of sodium carbonate to the hydroxide would result in an increase in the concentration of undissociated sodium hydroxide and thus increase the germicidal action. Because of the difficulty of measuring H-ion concentration a t this high alkalinity, the change due to addition of the carbonate would not be readily detected. The determination of H-ion concentration in the range pH 13.00 to 13.50 is subject to considerable error, and may therefore lead to anomalous results. Thus the commercial alkali (1.99 per cent NaOH plus 2.66 per cent NaZC03) gave a pH of 13.20, whereas an artificial mixture of approximately 2.70 per cent the same composition (2.0 per cent NaOH Na2C03) was p H 13.32. These H-ion readings corresponded to sodium hydroxide concentrations of 0.5 N and 0.725 N , respectively. The germicidal efficiencies of the commercial alkali (pH 13.20) and the artificial mixture (pH 13.32) were similar (killing times of 34 and 31.1 minutes, respectively), whereas the killing times for the corresponding sodium hydroxide solutions, on a pH basis, varied from 40 minutes
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at p H 13.20 to 22.8 minutes a t pH 13.32. Thus the artificial mixture and commercial alkali were about equally efficient germicides and superior to a 0.5 N and inferior to a 0.725 N sodium hydroxide. On comparing these solutions on the basis of H-ion concentration it is seen that the artificial mixture was less efficient and the commercial alkali more efficient than sodium hydroxide. This anomalous result is due to the difficulties inherent in determination of H-ion concentrations of solutions of alkalies in the range pH 13.00 to 13.50. A variation of 0.1 in pH is equivalent to a change of 1.0 per cent sodium hydroxide. Readings closer than 0.05 pH could hardly be obtained under very carefully controlled conditions. Herein lies a most serious obstacle in attempting to evaluate germicidal efficiencies of alkalies on a pH basis. Summary
The H-ion concentration was not a direct measure of the relative germicidal properties of sodium hydroxide as compared with sodium hydroxide-carbonate mixtures. At pH 13.2 to 13.4 and 50" C. the sodium hydroxide-carbonate mixtures contain less caustic alkali than the pure sodium hydroxide, and are less efficient germicides. On comparing sodium hydroxide with a commercial washing solution containing the same amount of sodium hydroxide (and in addition sodium carbonate) a t pH 12.99 to 13.20, the commercial product was found to be the better germicide, indicating that the sodium carbonate enhanced the disinfecting powers of the sodium hydroxide. This effect of the carbonate increased with temperature. It is suggested that the undissociated sodium hydroxide rather than the hydroxyl-ion concentration may be the controlling factor in disinfection with alkalies.
The Scientific Use of Nitrogen Fertilizers' Firman E. Bear THEOHIO STATE
UNIVERSITY, COLUHBUS, OHIO
HE controlling factor in determining the market price of fertilizer nitrogen is the cost of the synthetic production of compounds of this element. Improved technic is being applied to large-scale synthesis of compounds containing high percentages of nitrogen. As a result this element can be delivered to the field a t a unit cost t,hat is sufficiently low to offer attractive possibilities in a much enlarged use of it in crop production. It has been pointed out that,2notwithstanding the requirements of crop plants and the deficiences of soils, that plantfood compound which is available in the largest amounts in any country is used in largest proportion by the farmers of that country. Thus American farmers use more phosphates, Chilean farmers more nitrates, and German farmers more potash salts than do the farmers of other countries in which these materials are not so abundant. Within certain limits some fertilizer salts can be substituted for others with equally good effect. For example, phosphates stimulate bacterial fixation of nitrogen and thus serve as an indirect source of this element. Their correct use results in an enlarged root system of the plant, which increases its foraging power for potash and other nutrients in the soil. Thus, comparative trials of the same number of pounds each
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1 Presented before the Division of Fertilizer Chemistry at the 74th Meeting of the American Chemical Society, Detroit, Mich., September 5 to 10, 1927. * Curtis, A m . Fcrfiliecr, 64, No. 13, 73 (1926).
of a 2-12-2 and a 4 - 8 4 analysis may show almost identical effects on the crop during the earlier years of the test. The abundance of phosphates in this country and their low price makes it possible to use them more nearly up to the limit of their efficiency. They not only serve as sources of the elements phosphorus and calcium for direct use of crop plants, but also produce desirable indirect effects at a cost that is often less than that for which these effects can be secured by other means. A further explanation of the use of larger amounts of that fertilizer material which is available in greatest quantity a t a low price is the research that is fostered by the syndicates which have the product for sale and the propaganda which follows up each advance that is made in the knowledge as to the more efficient use of the material. Research finds the places where and the means by which a fertilizer salt can be made most effective. Propaganda and sales effort put the salt in these places and get it used efficiently. I n the event that the same effect can be secured by the use of either of two salts, price ultimately becomes the determining factor in deciding which will be used. The foregoing statements anticipate, in part, the story that is now being written for synthetic nitrogen. This element is being taken from the air in large amounts. Enormous quantities of its salts will eventually be synthesized and a t a lower cost per unit of nitrogen. Intensive studies are being made of possible means of securing-greater returns for each
