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The chemistry of the soil nitrogen
THE
CHEMISTRY
OF THE
SOIL
NITROGEN.
1
BY
SAMUEL
L. J O D I D I ,
B.S., P h . D .
(CONTRIBUTION FR05I THE CHEMICAL RESF,ARCIt LABORATORY, SOILS SECTION~ IOWA
AGRICULTURAL EXPERIMENT
STATION.)
THE question of plant food is one of the most important physiological problems confronting the plant physiologist, botanist, horticulturist, agronomist, forester, and, generally speaking, all those who have to deal with plants. It is of great moment both from a scientific and practical point of view. Increased knowledge as to how to utilize the plant food, especially the one which is already contained in the soil, seems to be the key for raising bigger crops and at less cost. It is with the soil nitrogen that this article is chiefly concerned with. The nitrogen contained in soils is made up of ammonia, nitrites, nitrates, and of organic compounds. The latter usually form the bulk of the soil nitrogen. Ill speaking, however, of nitrogen as plant food we, in a more limited sense, usually mean by that the so-called available nitrogen which is. necessary for the growth, development, multiplication, and, generally speaking, for all life functions of the plants. It is true that available nitrogen--ammonia and nitrates-is constantly coming to the soil with all kinds of precipitations, like rain, dew, snow, etc. As is well known, however, the total amount of available nitrogen obtained in this way is only a few pounds per acre. 2 The nitrogen in the form of commercial fertilizers is quite expensive, costing about I8 cents per pound. ~ Co,mmtmieated by the at~thor. "~According to exl~eriments conducted in Prussia, the total anlount of nitrogen coming into the soil with atmospheric precipitations is from 11.6 to I8.2 kilogrammes per hectare (lO.3 to 16.2 pounds per acre and year). See " Die Chemie in ihrer A n w e n d u n g auf Agricultur und Physiologie," J, v. Liebig, p. 44 (1876). According to later experiments, the amount of atmospheric nitrogen which reaches the soil is still smaller. 483
484
SAMUEL L. JODIDI.
True, the processes of Eyde and Haber will make it cheaper. Yet the cheapest and best source of nitrogen is the soil itself, which contains the remains of animals and plants, in all of which nitrogen is present, chiefly in the form of organic compounds. The latter, however, have not fully and advantageously been utilized because of our lack of knowledge concerning their chemical nature. In the light of the latest researches into the character of soil organic matter, and especially of soil organic nitrogen, the knowledge of the chemical nature of the organic nitrogenou,s co~npounds present in soi,ls represents the very means for the solution of the problem as to how fully to utilize the soil nitrogen. In this connection it is well to bear in mind that available nitrogen, in a wider sense, consists not merely of ammonia and nitrates present as such in soils, but also of those organic nitrogenous compounds which readily undergo the processes of alnmonification and nitrifi:cation. As to the amount of ammonia present as such in Michigan peat soils, it was shown a to be quite small,--namely, from about one-tenth to, one and one-hair per cent. of the total nitrogen contained in the peat. This was also shown to be true of Iowa 4 soils in which the total quantity of ammoniacal and nitric nitrogen ranged from one to somewhat more than 2 per cent., calculated to the total soil nitrogen. The extension of our investigations has demonstrated that the above facts hold also good for Iowa soils which were fertilized with various organic materials and grew" a considerable variety of crops. ~ In all of the above soils from 9 8 to 99 per cent. of the total soil nitrogen consisted of organic nitrog~enous compounds. The extraction of these compounds by boiling the soils with sulphuric or hydrochloric acid led to results showing that those organic compounds 6 were made up chiefly of acid amides, diamino acids, and monoamino acids. Since, however, acids are known to hydrolyze aJodidi, .% L.. fourn. Amer. Chem. Sot.. 32, 306 (I9IO) ; also Michigan Agr. College Exp. Sta. Techn. Bul., No. 4 (19o9). ~Jodidi, S. L., Jouru. Amer. Chem. Sot., 33, I226 (r9II); also Iowa State College Agr. Exp. Sta. Research Bul., No. I (IgII). \Jodidi, S. L.. Journ. Amer. Chem. Sot.. 34, 94 (I912) ; also Iowa State College Agr. Exp. Sta. Research Bu!.. No. 3 (1011). "Loc. cit.
T H E CHEMISTRY OF TIlE SOIL NITROGEN.
485
proteins which are always present in soils, the question naturally arises: Are those acid amides and amino acids--found in the acid extracts of the soils--as such contained in the soils, or are they merely decomposition products of the hydrolyzed proteins ? Just how much of the soil organic nitrogen is made up of proteins, and how nmch of acid amides, amino acids, or other nitrogenous compounds, and what the chemical nature of the latter is, cannot at present fully be answered. The investigations which systematically deal with the chemical nature of soil organic nitrogen date back only a few years and are still far from being completed. However, with the knowledge already at our command we are able to answer the above question in part. The consideration of the fact that tissues of plants and animals, on their death, are constantly coming into the soil, is proof that the latter must contain a part of its nitrogen in the form of proteins. The work of S. Suzuki, 7 namely, " Studies o,n' Humus F o r m a t i o n , " led him to the conclusion that humic acid-obtained by extraction with a 2 per cent. sodium hydroxide solut i o n - i s made up of proteins which are combined more or less intimately with the black substances. As early as 1873 W. Wolf s made the assumption that the organic nitrogenous compounds present in soils are of the acid amide type. In their investigations in connection with amides Berthelot 9 and Andrfi found that hydrolyzing means, such as alkalies, acids, or even water, split off a portion of the nitrogen contained in humus in the forln of ammonia. This, they concluded, must be due to the presence of amides in the soil. Based upon the fact that he found considerable amounts of ammonia in soils which were previously treated with acids or alkalies, but that ammonia as such was contained in the same soils in but minimum quantities, A. Baumann ~o suggested the possible presence of amino compounds in soils. The experiments of A. H6bert n have shown that when soil is heated with water to temperatures above IOO° C. the organic nitrogenous substances present in the soil split off their Bul. College Agr., Tokyo, 7, 513-529 (19o7). 8Landw. Jahrbiicher, 2, 389 (1873). 9Compt. rend., IO3, IiOI (1886). l°Land~v, r'ers.-Stat., 33, 247 (1887). UAnnales agronomlques, 15, 3~5 (1889). VoL. CLXXV,'No. IO49--32
486
SAMUEL L. JODIDI.
nitrogen in the form of ammonia. The results of his experiments go to show that the ammonia thus obtained is due to the occurrence in the soil of amido compounds. While the presence o.f amino nitrogen in soils was qualitatively demonstrated by Warington ~2 and Sestini, ~3 Dojarenko 14 estimated quantitatively the amounts of amido and amino nitrogen present in humic acid which he extracted from Russian black soils. The isolation of a definite organic compound from an Hawaiian soil was accomplished-by Shorey 1~ in 19o6 , who identified it as picoline carboxylic acid. The writer 16 was the first to show the presence of diamino acids in soils. While their presence was first demonstrated by him tfirough the application of the Hausmann ~7 method as modified by Osborne ~s and Harris, it was later verified and confirmed by the writer, 19 as well as by other investigators, 2° in a variety of ways. Inasmuch as the amino acids and acid amides make up a considerabl.e part of the acid extract of soils, it may be worth while to consider here those compounds somewhat at length. Theoretically, the primary disintegration products of proteins--acid amides, mono-amino acids, diamino acids--as well as lecithin derivatives, etc., may undergo chemical changes in the soil in a variety of ways. In case it is a simple hydrolytic process we would have the following equations: R"
CO" NH2 + H~O
= R"
Acid amide.
CO" OH + NH3 F a t t y acid.
R . CH. NH2' COOK -}- H20 = R . CH. OH. COOK + NH3 Mono-amino acid.
1~Chem. News~ 55, 27 ( I 8 8 7 ) . ~3Landw. Vers.-Stat., 51, 153 (1899).
H y d r o x y acid.
Abs. in Expt. Sta. Rec., IO, 424
(I898) •
l*Landw. Vers.-Stat., 56, 311 (19o2). Annual Report of the Hawaii Agr. Exp. Sta., I9O6, p. 52. ~'dourn. Amer. Chem. Soc., 32, 396 (191o); Michigan Agr. Exp. Sta. Tech. Bul., No. 4. ,aTZeit. physiol. Chem., 27, 95 (I899) ; 29, 136 (I9OO). ~SJourn. Amer. Chem. Soe.~ 25, 323 (19o3). ~ Loc. cit. 2O]ourn. Biol. Chem., vol. viii, No. 5, P. 381 (19IO).
THE
CHEMISTRY OF T H E SOIL NITROGEN.
487
In the latter case the leucine, for instance, would yield leucinic acid according to the equation : C H 3. 5 c\ H CH~/
CH2. C H . NH~. COOH +
CH~\
Leucine. H~O =
5 C H . CH2" CH • OH • COOH + NH~ CH3/ Leucini¢ acid.
Deamination of naono-amino acids can take place in such a way as to produce fatty acids according to the following schemes :
CH3"CH"
NH~. COOH
>
Alanine.
CH3' CH2'COOH Propionic acid.
CH
CH
CH//\c
CH//",CH
>
CH%/;CH
CH %,,/CH
C- CH,' CH. NH~- COOH
C. CH2. CH,. COOH
Phenylalanine. COOH • CH2' CH" NH2" C 0 0 H Aspartic acid.
Phenylpropionic acid.
>
COOH
• CH2' CH2" COOH Succinic acid,
Through fermentation the amino, acids can yield alcohols. Leucine, e.g., can give iso.butylcarbinol (arnylalcohol) according to the following equation: C H 3.~ c\ H CH~/
CHo. CHNH2. COOH + H~O = NH3 + CO, + Leucine.
CH~
CH. CH2" CH2" OH CH,
IsobuWlcarbinol.
Again, the diamino acids may split off C02 n.nder the formation of amines. Lysine, 21 for instance, is known to split off 2, Zeit. physiol. Chem., 29, 334 (I9OO).
488
SAMUEL L. JODIDI.
CO2, under the action of micro-organisms, whereby cadaverine (pentamethylene diamine) results: NH2.CH~.CH2" CH~. CH~. CH. NH2. COOH
>
CO~+
Lysine.
NH2. CH2. CH2" CH,.. CH~. CH2. NH2. Cadaverine.
in this connection it is interesting to note that the amines choline 22 and trinmthylamine were extracted from the soil. There can be little doubt, if any, that trimethylamine was formed in the soil secondarily from betaine, choline, and neurine, o f which betaine is as such widely distributed in the vegetable kiaagdorrl, and the neurine is closely related to choline, which latter, in turn, is a decomposition product of lecithin. The above can best be illustrated in the following way: /CH2' (CH~)3
CO
-- N(
! J
\O
Betaine.
>
(CH3)3
~
N
Trimethylamine.
CH~. O. R 25
I
CH-O.R
I
CH2' 0
H0--~,P6
C~H__O/ I
I
= N//CH2" CH2' OH
, (ClI~)~
> (CH~)~ = N,/cH
\0H Choline
= CH2
"OH Neurine
OH
(CH~)3N
(CH3)~N
Lecithin.
Trimethylamine.
Trimethylamine.
The trimethylamine having been found in the soil, it is but reasonable to assume that methylamine and dimethylamine will also be found in soils, since the above three amines equally occur as degradation products of rotted flesh, of lecithin-holding substances, etc. Shorey, E. C., original co,mmunications, V I I I Intern. Congress of Appl. Chem'., vol. xv, p. 249, ~ R stands for the radical of the fatty acids, like pahnitic, stearic, oleie, etc.
THE
CHEMISTRY
OF
THE
SOIL
489
NITROGEN.
Just as cadaverine can result secondarily from lysine--a primary cleavage product of proteins--putrescine can result secondarily from ornithine, which can be formed, e.g., from the protein cleavage product arginine through the enzyme arginase, or from ornithuric acid through hydrolysis. Hence, the occurrence in the soil of cadaverine, putrescine, and related amines is altogether not out of the question. The above can best be illustrated l~y the following equations: NH2. CH~. CH2- CH2' CH2. CH. NH2. COOH = CO2 + NH2" (CH~), • NH~ Lysine.
Cadaverine.
NH2' CH2" CH2" CH2" CH" NH~' COOH = COs + NH2" (CH2)4" NH~" Ornithine.
Putrescine.
NH2
NH2
I
I HN
= C. NH.
CH2' CH2. CH~. CH.
COOH
+ H20
/NH,+
= OC,,
"NH2
Arginine.
NH~. CH2. CH2. CH2" CH- NH2' COOH Ornithine.
The occurrence in the soil of picoline carboxylic acid, as well as of other pyridine derivatives, may very well be due to. the existence in the soil o,f vegetable residues containing a pyridine nucleus, bearing in mind that many plants produce alkaloids all of which are closely related to pyridine, their parent body. However, pyridine and its derivatives may also be fo,rmed from proteins. Lysine, for instance, which is a primary cleavage product of proteins, is known, under the action of micro-organisms, to yield pentamethylene diamine. The hydrochloride of the latter yields, on distillation, piperidine, which is hexahydropyridine. The above facts may find expression in the following way : Protein
)- NH2.
CH2 • CH2- CH2. CH2. CH. Lyslne.
NH~. COOH
CH2
CH~~ "'\ CH2 '
CH~\/CH.~ NH Piperidine.
<
N H 2 ' (CH2)5 • NH2
Cad. . . . inc.
49 °
SAMUEL L. JODIDI.
T h e r e can hardly be any doubt but that the primary formation of lysine from proteins and the secondary degradation of lysine to cadaverine actually take place in the soil, since- lysine 24 could be extracted from soils, and this diamino acid is known under the action of bacteria--so numerous in the soil--to split off carbon dioxide under the formation of pentamethylene diamine. Whether the latter can, under the influence of the agencies active in the soil, be converted into piperidine has not yet been demonstrated. Proteins, however, can, in the process of decomposition, yield pyridine compounds also in another way. It is fairly well known that some of the primary decomposition products of proteins, like lysine, tyrosine, tryptophane, and glucoseamine, secondarily yield humin substances. The latter, in turn, as was shown by Samuelyfl 5 yield, on reduction, pyridine. Intermediary products can be, and actually are being, formed in the soil when conditions in it are favorable for the process of putrefaction. When, however, conditions in the soil are favorable for the process of cremacansis--in case the soil is well drained, porous, well cultivated, and hence contains a good deal of a i r - - t h e organic substances will naturally, sooner or later, completely be destroyed under the formation of carbon dioxide, water, and ammonia. Do amino acids, acid amides, purine bases, etc., as such; occur in the soil ? This question must be answered in the affirmative. Aside from the fact that some of these compounds may come into the soil with manures, or may be formed in it as the result of degradation of protein bodies, we must not forget that the nitrogen in plants consists in part of amino acids as such. E. Schulze, 26 for instance, has shown that in beets but 21.6-38. 9 per cent. and in potatoes only 56.2 per cent. of the total nitrogen consists of protein bodies. Further, it was found by O. Kellner 27 that amino acids and acid amides occur quite generally in plants, sometimes in very considerable proportions. It matters **Original communications, VII[ Inter. Congress of Applied Chemistry, vol. ~v, p. 249. ~ Beitr. Chem. Physiol. u. Path., 2, 355 (I9o2). ~ L a n d w . Versuchsst., I8, 320 (I875) ; 2L 86 (I878) ; 69, 393 (I9O8). ~ Landw. Yahrb., 8 (I879).
T H E CHEMISTRY OF THE SOIL NITROGEN.
49 1
little whether those compounds are the result of degradation of proteins through the action of proteolytic enzymes, which is especially the case in germs of plants or in the young sprouts, or whether they represent transition products from the inorganic nitrogen (taken up by the plants) to the synthesis of proteins in the vegetable organism. The fact remains that acid amides and amino, acids as such occur in plants, and hence they naturally come, on the death of the plants, into the soil. Tl)e above statement does not stand in contradiction to the fact that water extracts of soils usually contain but small amounts of nitrogenous bodies other than ammonia and nitrates. It should be borne in mind that many organic nitrogenous compounds, especially the amino acids, are able to combine with mineral bases acids or salts in order to form double compounds. The latter show physical properties different from the amino acids, acid amides, etc., so far as, e.g., solubility in water is concerned. Again, amino acids, 2s purine bas.es,29 pyrimidine derivatives ~o and other 81 non-protein substances have directly been isolated at room temperature from a considerable number of soils,--namely, from weak (2 per c e n t . ) s o d i u m hydroxide soil extracts. Under these conditions of the isolation of the above compounds hydrolysis of protein substances cannot very well be assumed. The chemistry, then, of the organic nitrogenous compounds in soils can at present broadly be stated as follows: Under the action of proteolytic enzymes, micro-organisms, or chemical means, the proteins are decomposed--probably through the stages of albumoses, peptones, and polypeptides--chiefly to diamino acids, mono-amino acids, and acid amides. In addition to these products, there results also nucleic acid, in the case of nucleoproteids, which latter, on decomposition, "yield nucleins, and, further, proteins on the one hand, and purine bases, pyrimidine derivatives on the other. Furthermore, some non-protein sub~Journ. Biol. Chem., vol. viii, No. 5, P- 38r (191o). m Journ. Biol. Chem., vol. viii, No. 5, P. 385 (191o). 80Ibid.
alarm. Report Hawaii Agr. Exp. Sta., p. 37 (19o6) ; fourn. Amer. Chem. Soc., 34, 99 (I912).
492
SAi~IUEL L. JODIDI.
stances like acid amides and amino acids, as stated already, come as such into the soil with certain plants. As to the a,ccumulation in the soil of the nitrogenous compounds, it can safely be stated that the compounds which are more resistant to the above-mentioned agencies will be found in the soil in larger proportions than the less resistant substances. The amino acids and acid amides cannot accumulate in the soil to any extent, because they are easily alnmonified in it, as was shown in a recent publication, a2 It does not make, however, much difference whether at any time the acid amides and amino acids are present in the soil in smaller or larger quantities, if only the higher complex molecules ot' the proteins and nucleoproteids have to pass through the stage of the acid amides and amino acids before their nitrogen can be transformed into ammonia. The ammonia and nitrites, too, cannot accumulate in the soil, because of their ready oxidation to nitrates, which latter, again, are ordinarily encountered in soils in but small quantities, for the reason that they are eagerly taken up by plants, or leached out of the soil in case it is followed. It is only soil nitrogen in its initial stage--proteins and nucleoproteids--that is c'ommonly present in considerable quantities in the soil. The nitrogen in its final stage--nitrates--can, under certain conditions, accumulate in the soil. All other forms of nitrogen, both organic and inorganic compounds, represent transition stages and seem to be present in soils in but inconsiderable proportions. The acid amides and amino acids represent some of the organic nitrogenous compounds out of which ammonia is immediately form,ed. It thus can be seen that many of the organic nitrogenous compounds represent a great and important source from which the available nitrogen--ammonia and nitrates--is formed. Consequently, the problem of the formation and utilization of the available soil nitrogen is one which is intimately connected with the question of the chemical nature of the organic nitrogen. Schematically the chemistry of the soil nitrogen may be presented as follows: s'~Jodidi, S. L., original communications, V I I I International Congress of Applied Chemistry, vol. 26, p. I I9.
THE
CHEMISTRY
OF
THE
SOIL
NITROGEN.
493
Soil Nitrogen
I Inorganic N
Organic N
J
NH3 (Ammonia.) Taken up by plants, or transformed into nitrites and nitrates
I
• HN02 (Nitrites.) Oxidized to nitrates
•HNO~ (Nitrates.) Taken up by plants, or leached out of the soil in case it is fallowed
Proteins
Nucleoproteids
/
Nucleins
I
Nucleic acids
/
Non-protein substances (acid amides, amino acids, etc.)
/
Proteins
Purine bases and Pyrimidine bases
Albumoses
Peptones
Polypeptides
Diamino acids. / Mono-amino acids, Acid amides
Ammonia
Nitrites
Nitrates (see above) Diamino acids
Amines
Mono-amino acids
t
Humin substance
Pyridine
Alcohols Hydroxy F a t t y acids acids
Acid amides
494
SAMUEL L. JODIDI.
I n cojasidering the above scheme it should be borne in mind that it contains compounds which have actually been f o u n d in soils, or which, f r o m theoretical considerations, are likely to occur in soils. This scheme, however, does not represent the only w a y in which the various c o m p o u n d s m a y be f o r m e d in the soil. F o r instance, alcohols, fatty and h y d r o x y acids, can occur in the soil as the result of f e r m e n t a t i o n of carbohydrates. Equally, organic acids m a y be f o r m e d t h r o u g h oxidation of alcohols or t h r o u g h hydrolysis of n a t u r a l l y - o c c u r r i n g fats. H o w e v e r , a closer consideration of these and similar processes is beyond the province of this article. REFERENCES. I. Liebig, J. v., "Die Chemie in ihrer Anwendung auf Agricultur und Physiologie," p. 44 (1876). 2. Jodidi, S. L.. " The Utilization of Peat," Journ. Amer. Peat Society, vol. ii, No. 1 (19o9). 3- Suzuki, S., " Studies on Humus Formation," Bul. College of Agr., Tokyo Univ., vol. vii (I9O&I9o8). 4. Wolf, W., "Beitriige zur Begriindung der naturwissensehaftlichen Bonitirung der Ackererden," Landw. ]ahrbiicher, 2, 389 (1873). 5. Jodldi, S. L., "Organic Nitrogenous Compounds in Peat Soils," Michigan Agr. College Exp. Sta. Tech. Bul., No. 4; also Journ. Amer. Chem. Soc., 32, 396 (I9IO). 6. Berthelot and Andr6, " Sur les principes azot6s de la terre vegfitale," Comptes rendus, lO3, IiOI (I886). 7. Baumann, A., " Ueber die Bestimmung des im Boden enthaltenen Ammoniak-Stickstoffes und ueber die Menge des assimilirbaren Stickstoffes im unbearbeiteten Boden," Landw. Vers.-Stat., 33, 247 (1887). 8. Jodidi, S. L., "The Chemical Nature of the Organic Nitrogen in the Soil," Journ. Amer. Chem. Soc., 33, 1226 (1911). 9-Warington, R., "Some Recent Researches on the Nature of the Nitrogenous Organic Matter of Soils," The Chemical News, 55, 27 (1887). io. Sestini, F., "Der die HumussSure im Erdreich und Torfe begleltende Stickstoffgehalt," Landw. Vers.-gtat., 51, 153 (1899). ii. Jodidi, S. L., " The Chemical Nature of the Organic Nitrogen in the Soil," Iowa Agr. Exp. Sta. Research Bul., No. I ( I 9 I I ) . 12. Dojarenko, A., "Der Stickstoff des Humus," Landw. Vers.-Stat., 56, 311 (19o2). 13..Shorey, E. C., "Organic Nitrogen in Hawaiian Soils," Ann. Report Hawaii Agr. Exp. Sta. for 19o6. 14. Jodidi, S. L., and Wells. A. A., " Influence of Various Factors on Decomposition of Soil Organic Matter," Iowa Agr. Exp. gta. Research But, No. 3 (1911).
CURRENT TOPICS.
495
15. Hausmann, W., "Ueber die Vertheilung des Stickstoffs im Eiweissmolekfil," Zeit. physiol. Chem., 27, 95 (1899) ; 29, 136 (I9OO). 16. Schreiner, O., and Shorey, E. C., '"The Presence of Arginine and ttistidine in Soils," ]ourn. Biol. Chem., vol. viii, No. 5, P. 381; vol. viii, No. 5, P. 385 (I9IO). I7. Jodidi, S. L., " The Chemical Nature of the Organic Nitrogen in the Soil" (second paper), fourn. Amer. Chem. Soc., 34, 94 (1912). I8. Osborne, T. B., and Harris, I. F., "Nitrogen in Protein Bodies," ]ourn. Amer. Chem. Soc., 25, 323 (I9O3). 19. Samuely, F., "Ueber die aus Eiweiss hervorgehenden Melanine," Beitr. Chem. Physiol. u. Path., 2, 355 (19o2). 20. Sehulze, E., and Urieh, A., " Ueber die stickstoffhaltigen Bestandtheile der Futter-Rfiben," Landw. Vers.-Stat., 18, 320 (1875). 21. Jodidi, S. L., " Behavior of Amino Acids in the Soil," original communications, VIII Intern. Congress of Appl. Chem., vcyl. 26, p. 119. 22. Schulze, E., and Barbleri, J., "Ueber den Gehalt der Kartoffelknollen an Eiweisstoffen und an Amiden," Landw. Vers.-Stat., 21, 86 (1878). 23. Hdbert, A., " D e la formation de l'ammoniaque dans la terre arable," Annales agronomiques, I5, 355 (1889). 24. Jodidi, S. L., "The Behavior of Acid Amides in the Soil," JOURNAL OF THE FRANKLIN INSTITUTE,175, 245 (March, 1913). 25. Jodidi, S. L., "Nitrogen in Beet Land," American Sugar Industry, voI. xiil, N~. 11 (November, 19II). IOWA STATE COLLEGEjAmes, Iowa. T h e Specific H e a t of F i b r o u s M a t e r i a l s . OTTO DIETZ. (H/ochbl. Papierfabr., xliii, 3119.)---The specific heats of the animal and vegetable fibres v a r y only slightly f r o m one another, and are between the limits o.319 and o.33 I, so ~ar as cotton, silk, wooI, linen, hemp, wood-pulp, artificial sill<~ etc., are concerned. The mineral fibres have lower specific heats: thus, that of asbestos is o.25I and that of glass-wool is o.I57. T h e specific heat is practically unaffected by t e m p e r a t u r e or content of moisture. H e l i u m in G a s e s f r o m S p r i n g s . C. ~-~,~OUREUand A . ' LEPAPE. (Comptes Rendus, clv, I 9 7 . ) - - W h i l e the rare gases argon, krypton, xenon, and neon seem to occur in natural springs a p p r o x i m a t e l y in quantities of the same order as in the atmosphere, the p e r c e n t a g e of helium is sometimes far higher, and some springs in the C6te d'Or contain I o per cent. of helium in their total gas content, consisting of nitrogen and the rare gases. T h e Source Carnot at Santenaz yields I7,845 litres of helium per annum. This helium might be " y o u n g " (i.e., liberated as it is f o r m e d ) or "fossil" (i.e., liberated after long accumulation). T h e first assumption would require the disintegration of 91 tons of radium or of 500 million tons of pitchblende per year for the production of the helium, hence this seems out of tl~e question.
CHEMISTRY
OF THE
SOIL
NITROGEN.
1
BY
SAMUEL
L. J O D I D I ,
B.S., P h . D .
(CONTRIBUTION FR05I THE CHEMICAL RESF,ARCIt LABORATORY, SOILS SECTION~ IOWA
AGRICULTURAL EXPERIMENT
STATION.)
THE question of plant food is one of the most important physiological problems confronting the plant physiologist, botanist, horticulturist, agronomist, forester, and, generally speaking, all those who have to deal with plants. It is of great moment both from a scientific and practical point of view. Increased knowledge as to how to utilize the plant food, especially the one which is already contained in the soil, seems to be the key for raising bigger crops and at less cost. It is with the soil nitrogen that this article is chiefly concerned with. The nitrogen contained in soils is made up of ammonia, nitrites, nitrates, and of organic compounds. The latter usually form the bulk of the soil nitrogen. Ill speaking, however, of nitrogen as plant food we, in a more limited sense, usually mean by that the so-called available nitrogen which is. necessary for the growth, development, multiplication, and, generally speaking, for all life functions of the plants. It is true that available nitrogen--ammonia and nitrates-is constantly coming to the soil with all kinds of precipitations, like rain, dew, snow, etc. As is well known, however, the total amount of available nitrogen obtained in this way is only a few pounds per acre. 2 The nitrogen in the form of commercial fertilizers is quite expensive, costing about I8 cents per pound. ~ Co,mmtmieated by the at~thor. "~According to exl~eriments conducted in Prussia, the total anlount of nitrogen coming into the soil with atmospheric precipitations is from 11.6 to I8.2 kilogrammes per hectare (lO.3 to 16.2 pounds per acre and year). See " Die Chemie in ihrer A n w e n d u n g auf Agricultur und Physiologie," J, v. Liebig, p. 44 (1876). According to later experiments, the amount of atmospheric nitrogen which reaches the soil is still smaller. 483
484
SAMUEL L. JODIDI.
True, the processes of Eyde and Haber will make it cheaper. Yet the cheapest and best source of nitrogen is the soil itself, which contains the remains of animals and plants, in all of which nitrogen is present, chiefly in the form of organic compounds. The latter, however, have not fully and advantageously been utilized because of our lack of knowledge concerning their chemical nature. In the light of the latest researches into the character of soil organic matter, and especially of soil organic nitrogen, the knowledge of the chemical nature of the organic nitrogenou,s co~npounds present in soi,ls represents the very means for the solution of the problem as to how fully to utilize the soil nitrogen. In this connection it is well to bear in mind that available nitrogen, in a wider sense, consists not merely of ammonia and nitrates present as such in soils, but also of those organic nitrogenous compounds which readily undergo the processes of alnmonification and nitrifi:cation. As to the amount of ammonia present as such in Michigan peat soils, it was shown a to be quite small,--namely, from about one-tenth to, one and one-hair per cent. of the total nitrogen contained in the peat. This was also shown to be true of Iowa 4 soils in which the total quantity of ammoniacal and nitric nitrogen ranged from one to somewhat more than 2 per cent., calculated to the total soil nitrogen. The extension of our investigations has demonstrated that the above facts hold also good for Iowa soils which were fertilized with various organic materials and grew" a considerable variety of crops. ~ In all of the above soils from 9 8 to 99 per cent. of the total soil nitrogen consisted of organic nitrog~enous compounds. The extraction of these compounds by boiling the soils with sulphuric or hydrochloric acid led to results showing that those organic compounds 6 were made up chiefly of acid amides, diamino acids, and monoamino acids. Since, however, acids are known to hydrolyze aJodidi, .% L.. fourn. Amer. Chem. Sot.. 32, 306 (I9IO) ; also Michigan Agr. College Exp. Sta. Techn. Bul., No. 4 (19o9). ~Jodidi, S. L., Jouru. Amer. Chem. Sot., 33, I226 (r9II); also Iowa State College Agr. Exp. Sta. Research Bul., No. I (IgII). \Jodidi, S. L.. Journ. Amer. Chem. Sot.. 34, 94 (I912) ; also Iowa State College Agr. Exp. Sta. Research Bu!.. No. 3 (1011). "Loc. cit.
T H E CHEMISTRY OF TIlE SOIL NITROGEN.
485
proteins which are always present in soils, the question naturally arises: Are those acid amides and amino acids--found in the acid extracts of the soils--as such contained in the soils, or are they merely decomposition products of the hydrolyzed proteins ? Just how much of the soil organic nitrogen is made up of proteins, and how nmch of acid amides, amino acids, or other nitrogenous compounds, and what the chemical nature of the latter is, cannot at present fully be answered. The investigations which systematically deal with the chemical nature of soil organic nitrogen date back only a few years and are still far from being completed. However, with the knowledge already at our command we are able to answer the above question in part. The consideration of the fact that tissues of plants and animals, on their death, are constantly coming into the soil, is proof that the latter must contain a part of its nitrogen in the form of proteins. The work of S. Suzuki, 7 namely, " Studies o,n' Humus F o r m a t i o n , " led him to the conclusion that humic acid-obtained by extraction with a 2 per cent. sodium hydroxide solut i o n - i s made up of proteins which are combined more or less intimately with the black substances. As early as 1873 W. Wolf s made the assumption that the organic nitrogenous compounds present in soils are of the acid amide type. In their investigations in connection with amides Berthelot 9 and Andrfi found that hydrolyzing means, such as alkalies, acids, or even water, split off a portion of the nitrogen contained in humus in the forln of ammonia. This, they concluded, must be due to the presence of amides in the soil. Based upon the fact that he found considerable amounts of ammonia in soils which were previously treated with acids or alkalies, but that ammonia as such was contained in the same soils in but minimum quantities, A. Baumann ~o suggested the possible presence of amino compounds in soils. The experiments of A. H6bert n have shown that when soil is heated with water to temperatures above IOO° C. the organic nitrogenous substances present in the soil split off their Bul. College Agr., Tokyo, 7, 513-529 (19o7). 8Landw. Jahrbiicher, 2, 389 (1873). 9Compt. rend., IO3, IiOI (1886). l°Land~v, r'ers.-Stat., 33, 247 (1887). UAnnales agronomlques, 15, 3~5 (1889). VoL. CLXXV,'No. IO49--32
486
SAMUEL L. JODIDI.
nitrogen in the form of ammonia. The results of his experiments go to show that the ammonia thus obtained is due to the occurrence in the soil of amido compounds. While the presence o.f amino nitrogen in soils was qualitatively demonstrated by Warington ~2 and Sestini, ~3 Dojarenko 14 estimated quantitatively the amounts of amido and amino nitrogen present in humic acid which he extracted from Russian black soils. The isolation of a definite organic compound from an Hawaiian soil was accomplished-by Shorey 1~ in 19o6 , who identified it as picoline carboxylic acid. The writer 16 was the first to show the presence of diamino acids in soils. While their presence was first demonstrated by him tfirough the application of the Hausmann ~7 method as modified by Osborne ~s and Harris, it was later verified and confirmed by the writer, 19 as well as by other investigators, 2° in a variety of ways. Inasmuch as the amino acids and acid amides make up a considerabl.e part of the acid extract of soils, it may be worth while to consider here those compounds somewhat at length. Theoretically, the primary disintegration products of proteins--acid amides, mono-amino acids, diamino acids--as well as lecithin derivatives, etc., may undergo chemical changes in the soil in a variety of ways. In case it is a simple hydrolytic process we would have the following equations: R"
CO" NH2 + H~O
= R"
Acid amide.
CO" OH + NH3 F a t t y acid.
R . CH. NH2' COOK -}- H20 = R . CH. OH. COOK + NH3 Mono-amino acid.
1~Chem. News~ 55, 27 ( I 8 8 7 ) . ~3Landw. Vers.-Stat., 51, 153 (1899).
H y d r o x y acid.
Abs. in Expt. Sta. Rec., IO, 424
(I898) •
l*Landw. Vers.-Stat., 56, 311 (19o2). Annual Report of the Hawaii Agr. Exp. Sta., I9O6, p. 52. ~'dourn. Amer. Chem. Soc., 32, 396 (191o); Michigan Agr. Exp. Sta. Tech. Bul., No. 4. ,aTZeit. physiol. Chem., 27, 95 (I899) ; 29, 136 (I9OO). ~SJourn. Amer. Chem. Soe.~ 25, 323 (19o3). ~ Loc. cit. 2O]ourn. Biol. Chem., vol. viii, No. 5, P. 381 (19IO).
THE
CHEMISTRY OF T H E SOIL NITROGEN.
487
In the latter case the leucine, for instance, would yield leucinic acid according to the equation : C H 3. 5 c\ H CH~/
CH2. C H . NH~. COOH +
CH~\
Leucine. H~O =
5 C H . CH2" CH • OH • COOH + NH~ CH3/ Leucini¢ acid.
Deamination of naono-amino acids can take place in such a way as to produce fatty acids according to the following schemes :
CH3"CH"
NH~. COOH
>
Alanine.
CH3' CH2'COOH Propionic acid.
CH
CH
CH//\c
CH//",CH
>
CH%/;CH
CH %,,/CH
C- CH,' CH. NH~- COOH
C. CH2. CH,. COOH
Phenylalanine. COOH • CH2' CH" NH2" C 0 0 H Aspartic acid.
Phenylpropionic acid.
>
COOH
• CH2' CH2" COOH Succinic acid,
Through fermentation the amino, acids can yield alcohols. Leucine, e.g., can give iso.butylcarbinol (arnylalcohol) according to the following equation: C H 3.~ c\ H CH~/
CHo. CHNH2. COOH + H~O = NH3 + CO, + Leucine.
CH~
CH. CH2" CH2" OH CH,
IsobuWlcarbinol.
Again, the diamino acids may split off C02 n.nder the formation of amines. Lysine, 21 for instance, is known to split off 2, Zeit. physiol. Chem., 29, 334 (I9OO).
488
SAMUEL L. JODIDI.
CO2, under the action of micro-organisms, whereby cadaverine (pentamethylene diamine) results: NH2.CH~.CH2" CH~. CH~. CH. NH2. COOH
>
CO~+
Lysine.
NH2. CH2. CH2" CH,.. CH~. CH2. NH2. Cadaverine.
in this connection it is interesting to note that the amines choline 22 and trinmthylamine were extracted from the soil. There can be little doubt, if any, that trimethylamine was formed in the soil secondarily from betaine, choline, and neurine, o f which betaine is as such widely distributed in the vegetable kiaagdorrl, and the neurine is closely related to choline, which latter, in turn, is a decomposition product of lecithin. The above can best be illustrated in the following way: /CH2' (CH~)3
CO
-- N(
! J
\O
Betaine.
>
(CH3)3
~
N
Trimethylamine.
CH~. O. R 25
I
CH-O.R
I
CH2' 0
H0--~,P6
C~H__O/ I
I
= N//CH2" CH2' OH
, (ClI~)~
> (CH~)~ = N,/cH
\0H Choline
= CH2
"OH Neurine
OH
(CH~)3N
(CH3)~N
Lecithin.
Trimethylamine.
Trimethylamine.
The trimethylamine having been found in the soil, it is but reasonable to assume that methylamine and dimethylamine will also be found in soils, since the above three amines equally occur as degradation products of rotted flesh, of lecithin-holding substances, etc. Shorey, E. C., original co,mmunications, V I I I Intern. Congress of Appl. Chem'., vol. xv, p. 249, ~ R stands for the radical of the fatty acids, like pahnitic, stearic, oleie, etc.
THE
CHEMISTRY
OF
THE
SOIL
489
NITROGEN.
Just as cadaverine can result secondarily from lysine--a primary cleavage product of proteins--putrescine can result secondarily from ornithine, which can be formed, e.g., from the protein cleavage product arginine through the enzyme arginase, or from ornithuric acid through hydrolysis. Hence, the occurrence in the soil of cadaverine, putrescine, and related amines is altogether not out of the question. The above can best be illustrated l~y the following equations: NH2. CH~. CH2- CH2' CH2. CH. NH2. COOH = CO2 + NH2" (CH~), • NH~ Lysine.
Cadaverine.
NH2' CH2" CH2" CH2" CH" NH~' COOH = COs + NH2" (CH2)4" NH~" Ornithine.
Putrescine.
NH2
NH2
I
I HN
= C. NH.
CH2' CH2. CH~. CH.
COOH
+ H20
/NH,+
= OC,,
"NH2
Arginine.
NH~. CH2. CH2. CH2" CH- NH2' COOH Ornithine.
The occurrence in the soil of picoline carboxylic acid, as well as of other pyridine derivatives, may very well be due to. the existence in the soil o,f vegetable residues containing a pyridine nucleus, bearing in mind that many plants produce alkaloids all of which are closely related to pyridine, their parent body. However, pyridine and its derivatives may also be fo,rmed from proteins. Lysine, for instance, which is a primary cleavage product of proteins, is known, under the action of micro-organisms, to yield pentamethylene diamine. The hydrochloride of the latter yields, on distillation, piperidine, which is hexahydropyridine. The above facts may find expression in the following way : Protein
)- NH2.
CH2 • CH2- CH2. CH2. CH. Lyslne.
NH~. COOH
CH2
CH~~ "'\ CH2 '
CH~\/CH.~ NH Piperidine.
<
N H 2 ' (CH2)5 • NH2
Cad. . . . inc.
49 °
SAMUEL L. JODIDI.
T h e r e can hardly be any doubt but that the primary formation of lysine from proteins and the secondary degradation of lysine to cadaverine actually take place in the soil, since- lysine 24 could be extracted from soils, and this diamino acid is known under the action of bacteria--so numerous in the soil--to split off carbon dioxide under the formation of pentamethylene diamine. Whether the latter can, under the influence of the agencies active in the soil, be converted into piperidine has not yet been demonstrated. Proteins, however, can, in the process of decomposition, yield pyridine compounds also in another way. It is fairly well known that some of the primary decomposition products of proteins, like lysine, tyrosine, tryptophane, and glucoseamine, secondarily yield humin substances. The latter, in turn, as was shown by Samuelyfl 5 yield, on reduction, pyridine. Intermediary products can be, and actually are being, formed in the soil when conditions in it are favorable for the process of putrefaction. When, however, conditions in the soil are favorable for the process of cremacansis--in case the soil is well drained, porous, well cultivated, and hence contains a good deal of a i r - - t h e organic substances will naturally, sooner or later, completely be destroyed under the formation of carbon dioxide, water, and ammonia. Do amino acids, acid amides, purine bases, etc., as such; occur in the soil ? This question must be answered in the affirmative. Aside from the fact that some of these compounds may come into the soil with manures, or may be formed in it as the result of degradation of protein bodies, we must not forget that the nitrogen in plants consists in part of amino acids as such. E. Schulze, 26 for instance, has shown that in beets but 21.6-38. 9 per cent. and in potatoes only 56.2 per cent. of the total nitrogen consists of protein bodies. Further, it was found by O. Kellner 27 that amino acids and acid amides occur quite generally in plants, sometimes in very considerable proportions. It matters **Original communications, VII[ Inter. Congress of Applied Chemistry, vol. ~v, p. 249. ~ Beitr. Chem. Physiol. u. Path., 2, 355 (I9o2). ~ L a n d w . Versuchsst., I8, 320 (I875) ; 2L 86 (I878) ; 69, 393 (I9O8). ~ Landw. Yahrb., 8 (I879).
T H E CHEMISTRY OF THE SOIL NITROGEN.
49 1
little whether those compounds are the result of degradation of proteins through the action of proteolytic enzymes, which is especially the case in germs of plants or in the young sprouts, or whether they represent transition products from the inorganic nitrogen (taken up by the plants) to the synthesis of proteins in the vegetable organism. The fact remains that acid amides and amino, acids as such occur in plants, and hence they naturally come, on the death of the plants, into the soil. Tl)e above statement does not stand in contradiction to the fact that water extracts of soils usually contain but small amounts of nitrogenous bodies other than ammonia and nitrates. It should be borne in mind that many organic nitrogenous compounds, especially the amino acids, are able to combine with mineral bases acids or salts in order to form double compounds. The latter show physical properties different from the amino acids, acid amides, etc., so far as, e.g., solubility in water is concerned. Again, amino acids, 2s purine bas.es,29 pyrimidine derivatives ~o and other 81 non-protein substances have directly been isolated at room temperature from a considerable number of soils,--namely, from weak (2 per c e n t . ) s o d i u m hydroxide soil extracts. Under these conditions of the isolation of the above compounds hydrolysis of protein substances cannot very well be assumed. The chemistry, then, of the organic nitrogenous compounds in soils can at present broadly be stated as follows: Under the action of proteolytic enzymes, micro-organisms, or chemical means, the proteins are decomposed--probably through the stages of albumoses, peptones, and polypeptides--chiefly to diamino acids, mono-amino acids, and acid amides. In addition to these products, there results also nucleic acid, in the case of nucleoproteids, which latter, on decomposition, "yield nucleins, and, further, proteins on the one hand, and purine bases, pyrimidine derivatives on the other. Furthermore, some non-protein sub~Journ. Biol. Chem., vol. viii, No. 5, P- 38r (191o). m Journ. Biol. Chem., vol. viii, No. 5, P. 385 (191o). 80Ibid.
alarm. Report Hawaii Agr. Exp. Sta., p. 37 (19o6) ; fourn. Amer. Chem. Soc., 34, 99 (I912).
492
SAi~IUEL L. JODIDI.
stances like acid amides and amino acids, as stated already, come as such into the soil with certain plants. As to the a,ccumulation in the soil of the nitrogenous compounds, it can safely be stated that the compounds which are more resistant to the above-mentioned agencies will be found in the soil in larger proportions than the less resistant substances. The amino acids and acid amides cannot accumulate in the soil to any extent, because they are easily alnmonified in it, as was shown in a recent publication, a2 It does not make, however, much difference whether at any time the acid amides and amino acids are present in the soil in smaller or larger quantities, if only the higher complex molecules ot' the proteins and nucleoproteids have to pass through the stage of the acid amides and amino acids before their nitrogen can be transformed into ammonia. The ammonia and nitrites, too, cannot accumulate in the soil, because of their ready oxidation to nitrates, which latter, again, are ordinarily encountered in soils in but small quantities, for the reason that they are eagerly taken up by plants, or leached out of the soil in case it is followed. It is only soil nitrogen in its initial stage--proteins and nucleoproteids--that is c'ommonly present in considerable quantities in the soil. The nitrogen in its final stage--nitrates--can, under certain conditions, accumulate in the soil. All other forms of nitrogen, both organic and inorganic compounds, represent transition stages and seem to be present in soils in but inconsiderable proportions. The acid amides and amino acids represent some of the organic nitrogenous compounds out of which ammonia is immediately form,ed. It thus can be seen that many of the organic nitrogenous compounds represent a great and important source from which the available nitrogen--ammonia and nitrates--is formed. Consequently, the problem of the formation and utilization of the available soil nitrogen is one which is intimately connected with the question of the chemical nature of the organic nitrogen. Schematically the chemistry of the soil nitrogen may be presented as follows: s'~Jodidi, S. L., original communications, V I I I International Congress of Applied Chemistry, vol. 26, p. I I9.
THE
CHEMISTRY
OF
THE
SOIL
NITROGEN.
493
Soil Nitrogen
I Inorganic N
Organic N
J
NH3 (Ammonia.) Taken up by plants, or transformed into nitrites and nitrates
I
• HN02 (Nitrites.) Oxidized to nitrates
•HNO~ (Nitrates.) Taken up by plants, or leached out of the soil in case it is fallowed
Proteins
Nucleoproteids
/
Nucleins
I
Nucleic acids
/
Non-protein substances (acid amides, amino acids, etc.)
/
Proteins
Purine bases and Pyrimidine bases
Albumoses
Peptones
Polypeptides
Diamino acids. / Mono-amino acids, Acid amides
Ammonia
Nitrites
Nitrates (see above) Diamino acids
Amines
Mono-amino acids
t
Humin substance
Pyridine
Alcohols Hydroxy F a t t y acids acids
Acid amides
494
SAMUEL L. JODIDI.
I n cojasidering the above scheme it should be borne in mind that it contains compounds which have actually been f o u n d in soils, or which, f r o m theoretical considerations, are likely to occur in soils. This scheme, however, does not represent the only w a y in which the various c o m p o u n d s m a y be f o r m e d in the soil. F o r instance, alcohols, fatty and h y d r o x y acids, can occur in the soil as the result of f e r m e n t a t i o n of carbohydrates. Equally, organic acids m a y be f o r m e d t h r o u g h oxidation of alcohols or t h r o u g h hydrolysis of n a t u r a l l y - o c c u r r i n g fats. H o w e v e r , a closer consideration of these and similar processes is beyond the province of this article. REFERENCES. I. Liebig, J. v., "Die Chemie in ihrer Anwendung auf Agricultur und Physiologie," p. 44 (1876). 2. Jodidi, S. L.. " The Utilization of Peat," Journ. Amer. Peat Society, vol. ii, No. 1 (19o9). 3- Suzuki, S., " Studies on Humus Formation," Bul. College of Agr., Tokyo Univ., vol. vii (I9O&I9o8). 4. Wolf, W., "Beitriige zur Begriindung der naturwissensehaftlichen Bonitirung der Ackererden," Landw. ]ahrbiicher, 2, 389 (1873). 5. Jodldi, S. L., "Organic Nitrogenous Compounds in Peat Soils," Michigan Agr. College Exp. Sta. Tech. Bul., No. 4; also Journ. Amer. Chem. Soc., 32, 396 (I9IO). 6. Berthelot and Andr6, " Sur les principes azot6s de la terre vegfitale," Comptes rendus, lO3, IiOI (I886). 7. Baumann, A., " Ueber die Bestimmung des im Boden enthaltenen Ammoniak-Stickstoffes und ueber die Menge des assimilirbaren Stickstoffes im unbearbeiteten Boden," Landw. Vers.-Stat., 33, 247 (1887). 8. Jodidi, S. L., "The Chemical Nature of the Organic Nitrogen in the Soil," Journ. Amer. Chem. Soc., 33, 1226 (1911). 9-Warington, R., "Some Recent Researches on the Nature of the Nitrogenous Organic Matter of Soils," The Chemical News, 55, 27 (1887). io. Sestini, F., "Der die HumussSure im Erdreich und Torfe begleltende Stickstoffgehalt," Landw. Vers.-gtat., 51, 153 (1899). ii. Jodidi, S. L., " The Chemical Nature of the Organic Nitrogen in the Soil," Iowa Agr. Exp. Sta. Research Bul., No. I ( I 9 I I ) . 12. Dojarenko, A., "Der Stickstoff des Humus," Landw. Vers.-Stat., 56, 311 (19o2). 13..Shorey, E. C., "Organic Nitrogen in Hawaiian Soils," Ann. Report Hawaii Agr. Exp. Sta. for 19o6. 14. Jodidi, S. L., and Wells. A. A., " Influence of Various Factors on Decomposition of Soil Organic Matter," Iowa Agr. Exp. gta. Research But, No. 3 (1911).
CURRENT TOPICS.
495
15. Hausmann, W., "Ueber die Vertheilung des Stickstoffs im Eiweissmolekfil," Zeit. physiol. Chem., 27, 95 (1899) ; 29, 136 (I9OO). 16. Schreiner, O., and Shorey, E. C., '"The Presence of Arginine and ttistidine in Soils," ]ourn. Biol. Chem., vol. viii, No. 5, P. 381; vol. viii, No. 5, P. 385 (I9IO). I7. Jodidi, S. L., " The Chemical Nature of the Organic Nitrogen in the Soil" (second paper), fourn. Amer. Chem. Soc., 34, 94 (1912). I8. Osborne, T. B., and Harris, I. F., "Nitrogen in Protein Bodies," ]ourn. Amer. Chem. Soc., 25, 323 (I9O3). 19. Samuely, F., "Ueber die aus Eiweiss hervorgehenden Melanine," Beitr. Chem. Physiol. u. Path., 2, 355 (19o2). 20. Sehulze, E., and Urieh, A., " Ueber die stickstoffhaltigen Bestandtheile der Futter-Rfiben," Landw. Vers.-Stat., 18, 320 (1875). 21. Jodidi, S. L., " Behavior of Amino Acids in the Soil," original communications, VIII Intern. Congress of Appl. Chem., vcyl. 26, p. 119. 22. Schulze, E., and Barbleri, J., "Ueber den Gehalt der Kartoffelknollen an Eiweisstoffen und an Amiden," Landw. Vers.-Stat., 21, 86 (1878). 23. Hdbert, A., " D e la formation de l'ammoniaque dans la terre arable," Annales agronomiques, I5, 355 (1889). 24. Jodidi, S. L., "The Behavior of Acid Amides in the Soil," JOURNAL OF THE FRANKLIN INSTITUTE,175, 245 (March, 1913). 25. Jodidi, S. L., "Nitrogen in Beet Land," American Sugar Industry, voI. xiil, N~. 11 (November, 19II). IOWA STATE COLLEGEjAmes, Iowa. T h e Specific H e a t of F i b r o u s M a t e r i a l s . OTTO DIETZ. (H/ochbl. Papierfabr., xliii, 3119.)---The specific heats of the animal and vegetable fibres v a r y only slightly f r o m one another, and are between the limits o.319 and o.33 I, so ~ar as cotton, silk, wooI, linen, hemp, wood-pulp, artificial sill<~ etc., are concerned. The mineral fibres have lower specific heats: thus, that of asbestos is o.25I and that of glass-wool is o.I57. T h e specific heat is practically unaffected by t e m p e r a t u r e or content of moisture. H e l i u m in G a s e s f r o m S p r i n g s . C. ~-~,~OUREUand A . ' LEPAPE. (Comptes Rendus, clv, I 9 7 . ) - - W h i l e the rare gases argon, krypton, xenon, and neon seem to occur in natural springs a p p r o x i m a t e l y in quantities of the same order as in the atmosphere, the p e r c e n t a g e of helium is sometimes far higher, and some springs in the C6te d'Or contain I o per cent. of helium in their total gas content, consisting of nitrogen and the rare gases. T h e Source Carnot at Santenaz yields I7,845 litres of helium per annum. This helium might be " y o u n g " (i.e., liberated as it is f o r m e d ) or "fossil" (i.e., liberated after long accumulation). T h e first assumption would require the disintegration of 91 tons of radium or of 500 million tons of pitchblende per year for the production of the helium, hence this seems out of tl~e question.