Melamine of Possible Plant Food Value WALTER SCHOLL, R. 0. E. DAVIS Bureau of Chemistry and Soils
E. E. BROWN AND F. R. REID Bureau of Plant Industry, Dspertment of Agricultum, Washington, D. C.
A
MONG the derivatives of cyanamide are several that have been shown to possess fertilizing properties, particularly urea and t,o some degree certain guanidine compounds. Dicyanodiamide, a polymerization product of two molecules of cyanamide, may he formed under some conditions in the soil in the transformat i o n of calcium cyanamide; wheii present in excessive amounts, i t has been found to be toxic or an inhibitor to the utilization of its nitrogen hy the plant. Melamine, also a polymeizatiou Droduct but eontainine. three molecules-of cyanamide instead of two, is formed with other products by heating dicyanodiamide to 150" C. Guanidine is obtained by ammonolysis of cyanamide, and recently Jones and Aldred (5) showed that by treatment of cyanamide with diammonium phosphate under autoclave conditions a t 140' C., the cyanamide may be converted largely to guanidine and small amounts of u r e a m d ammonia. Other methods have been proposed for preparing guanidine by treatment of cyanamide with ammonium salts (8) or of calcium cyanamide with ammonium nitrate (4). During the work on ammoniated peat (8) i t was suggested that heating cyanamide with liquid ammonia in an autoclave might give a high conversion to guanidine. Smce no cyanamide was available a t tho time, dicyanodiamide was treated with liquid ammonia with the result that a mixture was produced with the major constituent melamine.
guanylurea or cyanamide. Further examination of the product showed it to he principally melamine. This indicated that themain reaction took plme in two steps as shown by equations 1 and 2. IXcyanodiamiue w a s partly split into cyanamide which in turn reacted with dicyanodiamide to form the po1merization Droduct, melamine. Williams (7) pointed out that dicyanodiamide heated a t 150" C. forms melamine and melam. No examination for nielam was made on the product obtained here. NE-
4"'
---tZN&NHj
(1)
\NHCN
"=
+NdNH, ~ H C N
3 H,N
dN-cT \N
N d
N&
Additional material prepared by the same method hut using larger quantities of source materials gave 150 grams of product. This was recrystallized from water, and the mother liquor and alcohol washings were examined by Gerhy's method (3) for dicyanodiamide with negative results, hut cold water washings of the crystallined product gave a positive test. Examination of the recrystallized product by the same method gave a negative test for dicyanodiamide. Bawd on the dry dicyanodiamide employed, the yield of melamine w m about 80 per cent; 10 per cent of the dicyanodiamide remained in the cold water washings, and 10 per cent was converted to other products. Two experiments were carried out with the object of producing guanidine carbonate. I n each case 7.5 grams of dicyanodiamide, 14.1 grams of ammonium carbamate, and 1.0 gram of solid carbon dioxide were charged in an autoclave.
Experimental Procedure Preliminary experiments were conducted by treating 10 grams of pure dicyanodiamide with 20 grams of liquid ammonia in an autoclave of 100-d. capacity. The autoclave required 2 hours 40 minutes to reach a temperature of 155" C., which was maintained for 2 hours. It was then cooled in solid carbon dioxide-alcohol mixture before opening. After allowing excess ammonia to escape, the product obtained consisted of a white powder, about one-third of which was fused colorless crystals. The whole product was recrystallized from water, and qualitative tests were made by the method of Buchanan ( 1 ) for identification of some of the constituents. Positive identification waa obtained for dicyanodiamide, guanidine, and melamine; no evidence was obtained for 202
FEBRUARY, 1937
INDUSTRIAL AND ENGINEERING CHEMlSTRY
To one autoclave were added 2.6 grams of water and to the other, 20 grams of water. The autoclave charge was heated for 10 minutes a t 133" C. The products after discharge from the autoclave were recrystallized from water solution. Examination showed them to be composed of about 75 per cent melamine and 25 per cent guanidine carbonate in each case. Williams (6) indicated that ammelide also formed under similar conditions, but the products were not examined for this material since the melamine and guanidine carbonate made up practically the entire amount. Melamine recrystallized from the product as prepared from dicyanodiamide by treatment with twice its weight of anhydrous ammonia was employed for the preparation of melamine salts to be used in vegetative tests. Since melamine is a strong base, it readily forms salts with acids. Melamine sulfate! phosphate, and nitrate were prepared by treating melamine with dilute acid containing about 10 per cent excess acid over the required stoichiometric amount. The crystallized salts were separated, washed, and recrystallized from water solution. The analyses of the products indicated their empirical formulas and composition to be as follows: Total N (Dry Basis), %
203
Water Culture Tests Wheat was employed in the water culture tests. Five bottles, of 250-ml. capacity each with ten plants to each bottle, were used per treatment, and values were obtained for fifty plants. The culture solution contained 80 p. p. m. of nitrogen of the indicated nitrogen carrier, 160 p. p. m. PzOs from monocalcium phosphate, and 80 p. p. m. potassium oxide from potassium sulfate. The solutions were changed periodically, about every 3 or 4 days. The results obtained are shown in Table I. Series 1 continued for 25 days and series 2 for 22 days. Melamine sulfate culture early manifested a harmful reaction; the plants developed tip burn, and a t the end of the experiment they were in a dying condition. Green algae developed in the urea and sodium nitrate culture markedly, and to a somewhat less extent in melamine nitrate, but were absent in the other cultures. I n series 2, on the last change of solution, the p H was determined before the plants were placed in the solution and after they had been in the solution for 5 days:
Acid Radical (Dry Basis), yo
PH before 4.0 4.4 4.0 3.8 3.8 3.8
Melamine sulfate
7 Melamine phosphate
Compound Melamine sulfate (CaHeNe)n.HzS6r.H10 Melamine phosphate (C1HeNs)a.(HaP01);.2H10 Melamine nitrate, (CsHeNe).HNOa
TheoretiFound aal
TheoretiFound aal
45.4 45.6
SO3
22.01 21.7
39.8 41.3
PzOs
24.8
23.3
50.6 51.8
N (as NOa)
10.3
7.4
The approximate solubilities of melamine and the sulfate, phosphat,e, and nitrate salts were determined in water a t 29" C. Weighed quantities of material were placed in a flask with 200 ml. of water and allowed to remain in contact for 48 hours, during 14 hours of which the flasks were shaken. Weighed Gooch crucibles were used to collect the undissolved salt, the filtrate being employed to wash all undissolved salt onto the filter. After drying the Gooch crucibles a t 110' C. for 24 hours, the amount of original material dissolved was determined by weighing, with the following results: Soly. at 29" C Gram/ 100 Grams %ater (99.6%) 0.62 sulfate (99.7'7 ), (CaHeNe.)z~HzSOr~2HzO 0.19 phosphate (CPaHsNe)a,(HsPOr)n.4H*O 0.43 nitrate (C:HsNo) ."03.i/aHz0 0.68 Compound
Melamine Melamine Melamine Melamine
These salts were employed in a series of preliminary water culture and pot tests to obtain information on the availability of the nitrogen carried by them.
Melamine nitrate Urea NaNOs (NHdnSO4 NaNOa
+
pH after 5 Days 3.8 4.0 4.8 4.2 3.8 6.8
Very little change was evident with the exception of melamine nitrate and sodium nitrate; the first became less acid and the latter practically neutral. As shown in Table I and in Figure 1, melamine nitrate gave favorable results in both series, but the results from the other two melamine salts were not so good. An interesting feature of the melamine nitrate treatment is the extensive root development. Still another point of interest is the high transpiration with melamine nitrate, 1120 and 1117 grams of water in the two experiments; for the sodium nitrateammonium sulfate treatment this was only 568 and 895 grams in the two series, and for sodium nitrate in the second series, 1420 grams. Transpiration for all the others was very much less. The transpiration results were probably influenced to some extent by the varying reactions induced by the treatments. The results presented fail to show, except perhaps indirectly, that the nitrogen of melamine itself is absorbed and assimilated by the wheat plants. What part the nitrate nitrogen in melamine nitrate plays in the growth, transpiration, and root development is being studied in additional tests in which a n amount of nitrate nitrogen equivalent to that in melamine
COMPOUNDS" TABLEI. WATERCULTURESTUDYWITH ORGANICNITROGEN (In grams) Nitrogen Material
Transpi- -Green ration Tops
Wt.bRoots
Melamine sulfate Melamine phosphate Melamine nitrate Cyanuric acid a Urea NaNOs- , ( N H-,I~SOI
415.3 533.2 1120.3 385.3 491.3 568.2
4.73 0.46 10.8 4.51 9.45 10.73
3.55 3.97 6.20 2.95 3.82 4.31
Melamine sulfate Melamine phosphate Melamine nitrate Cyanuric acid Urea NaNOa (NHdrSO4 NaNOs Cyanuric acid CaCOa
531.5 748.7 1117.4 642.2 835.1 895.8 1420.6 870.1
4.22 4.15 7.13 5.06 9.40 11.04 14.71 4.96
3.96 5.65 7.97 4.75 5.88 4.81 8.90 7.34
+.
-Dry W t . 7 -Total Wt.-Green Tops Roots Green Dry Tops Series 1, September 8 to October 3 1.67 44 8.28 1.07 0.60 60 10.43 2.00 1.27 0.73 1.75 0.75 17.00 2.50 104.4 42 7.46 1.43 0.95 0.48 88 1.61 0.67 13.27 2.28 1.70 0.66 15.04 2.36 100 Series 2. Ootober 17 to November 8 38.2 8.18 1.47 0.93 0.54 37.6 9.80 1.57 0.94 0.63 64.5 1.39 0.69 15.10 2.08 45.8 9.81 1.71 1.13 0.58 1.68 0.68 15.28 2.30 85.1 1.85 0.63 15.86 2.48 100 3.05 133 2.14 0.91 23.61 1.07 0.91 12.30 1.98 44.9 ~~~
+
+
~~
.
~~
Wt.Roots
Relative Values -Dry Wt.-Total Tops Roots Green
Transpiration
82 92.1 143.9 69 89 100
63 74.7 103 50 94.7 100
90.9 110.0 113.6 72.7 101.5 100
55.1 69.4 113 49.6 88.2 100
70.7 84.7 105.8 60.6 96.6 100
73.1 93.8 197.0 67.6 86.5 100
82.3 117.4 165.5 98.8 122.2 100 185.0 152.6
50.3 50.8 76.2 61.1 90.8 100 115.7 57.8
85.7 100 109.5 92.1 108 100 144.6 144.6
51.6 61.8 95.2 61.9 96.4 100 149 77.6
69.3 63.4 83.9 69.0 95.2 100 123 79.9
59.4 83.5 124.6 71.6 93.2 100 159.1 97.8
~~
Water c*tw,e solutions: 80 p. p. m. N , 160 p. p. m. Pros aa c. P. monocalcium phosphate, 80 p. p. m. KtO a8 c. b Five replications of ten plants each. Cyanuric acid was included in the series as a compound related t o urea and melamine.
0
Wt.Dry
P.
potassium sulfate.
INDUSTRIAL AND ENGINEERING CHEMISTRY
204
a
I
3
5
4
6
7
FIGURE 2. Par TESTSivmn MELAMIXE SALTSON HDNQARIAN MILLET 1. "res; 2 , ammonium suliste: 3 sodium nitrate: 4. Bmmonium nitrate: 5 . melamine pliosphatr: 6 , melu6ine nitrate: 7 . phosphorus plus pota~sium
nitrate is furnished by standard sources of nitrate nitrogene . g., sodium nitrate or calcium nitraie.
Pot Test with Millet Following the water culture tests wibh melamine salts, preliinlinary pot tests were carried out, first employing German millet. The results of these test,s are shown in Table 11. Of the inelanline salts, the nitrate mas again best. The melamine nitrate gave yields practically equivalent t o those for urea and calcium cyanamide hut below the value for sodium nitrate.
Melamine nitrate Melamina phosphate Melamine sulfhte Bodiurn nitrate Ammonium sulfate Urea Calcium oYeasmide Dued blood P K (oiieek)
-
Melamine nitrate
Melamine p b u s p l ~ ~ t e Sodium nitrate Ammonium auliate Ammonium nitrste Urea
c. s. mea1 P
- B (oheckl
45.7 29.7 31.6 w2.5 56.3 45.1
46.0 55.1 29.4 15.45
9.70 28.65 36.45
37.10 35.35
37.60 7.90
16.8 0.3 2.1
231.1 26.9 15.7
16.6 25.7
...
8.55
1.80
30.75
28.55
?9.20
155.4
101.0 107.1
178.5
191.4 153.4
156.4
187.4
inn
196 12%
363 461 470
27.60
447
'29.60
414
...
A second series of pot tests employing Hungarian millet as an indicator plant did not give as favorable results for melamine nitrate. The results are shown in Table I1 and Figure 2; the melamine phosphate gave a yield about 60 per cent of that obtained from melamine nitrate, and melamine nitrate was about 100 per cent greater than the
VOL. 29, NO. 2
ptiosphorus-potassium check, 44 per cent of the urea, and 54 per cent of the sodium nitrate yield. The amount of nitrogen as nitrate in the melamine nitrate is only 14.5 per cent of the total nitrogen in the compound, or of that used with each of the materials. The pot tests are inconclusive as to the value of melamine nitrate, so that the results are to he considered as preliminary. For a better evaluation it mill be necessary to employ several rates of application of nitrogen, to vary the time of planting after the fertilizer application, to consider the soil reaction, to vary the crops and soil types, and to apply nitrate nitrogen in amounts equivalent. to that furnished by melamine nitrate. Of these proposed studies for the better evaluation of melamine oompounds as plant food materials, particnlar importance is to he ascribed to a comparison of different rates nitrogen application from melamine sources and to equivalent nitrat.e nitrogen supplies. These points are being given consideration in additional vegetative tests now in progress.
Nitrification Tests h series of nitrification tests was carried out over a period of 13 weeks on the three melamine salts with the use of ainmonium sulfate and R soil check sample for comparison. Tho results obtained indicated that ahout 1 per cent of the nitrogen in the melamine radical was converted to nitrate during this period. in contrast to a conversion of 80 per cent for ammonium sulfate. Summary Treat.ing dicyanodianiide with liquid ammonia in the ratio of 1 to 2 in an autoclave a t 155' C. for about 2 hours gave a white cryst,alline product containing 80 per cent melamine and 10 per cent dicyanodiamide. Two treatments were carried out on dicyanodiamide with ahout twice its weight of ammonium carbonat.e and one-seventh of carbon dioxide and, in one case, with one-third its weight of water and, in the other, three times its weight. The products in both eases contained 75 per cent melamine and 25 per cent guanidine carbonate. Material prepared hy the first method was recrystallized and used for the preparation of melamine salts for vegetative and nitrification tests. I n water culture tests, melamine nitrate gave results better than melamine phosphate or sulfate. In one of the tests melamine nitrate gave better results but in the other test somewhat lower results than urea or ammonium sulfate and sodium nitrate. The influence of the nitrate nitrogen furnished by melamine nitrate and the effectof the treatments on reaction were probably factors in giving the results obtained. Preliminary pot tests with German millet were similar. The melamine nitrate gave n plant yield practically t.he same as urea and cyanamide, hut a lower yield value than was obtained when using sodium nitrate as a source of nitrogen. Pot tests with Hungarian millet gave yields with melamine nitrate double that obtained from the phosphorus-potassium check but considerably below those from urea and sodium nitrate. One of tlie chief points of interest connected with these and subsequent vegetative tests is whether the growth response is due primarily to the nitrate nitrogen in melamine nitrate, particularly in view of the nitrification t.ests which indicated that very little of the melamine nitrogen is converted to nitrate during a 13-week period.
FEBRUARY, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
Acknowledgment The writers are indebted to L. A. Pinck for assistance i n identifying and analyzing some of the products.
205
(4)Gocket, H., Angew. Chem., 47, 555 (1934). ( 5 ) Jones, R. M., and Aldred, J. W. H., IND ENG.CHEM.,28, 272 (1936). (6) Williams, H.E.,"Chemistry of Cyanogen Compounds," p. 20 (1915).
(7) Ibid.,
Literature Cited (1) Buchanan, IND. ENG.CHEM.,15, 637 (1923). (2) Davis, R. 0. E . , Scholl, w., and Miller, R. R.,I b i d . , 27, 69 (1935), (3) Garby, C. D., Ibid., 17,266 (1925).
p.
24.
(8) Ibid., p. 25. RECEIVED September 12, 1936. Presented before the Division of F e r t i l i ~ e r Chemistry a t the QZnd Meeting of the American Chemical Society, Pittsburgh, Pa., September 7 t o 11, 1936.
Vulcanization Characteristics of Mercaptobenzothiazole Derivatives M. W. HARMAN Monsanto C h e m i c a l C o m p a n y , Nitro, W. Va.
The results of standardized vulcanization tests on forty-five condensation derivatives of mercaptobenzothiazole are reported. The materials alone and with added diphenylguanidine were compounded in a g u m stock and examined for curing value and scorching tendency. Twenty-seven of t h e compounds show upon activation a curing value equal t o or greater than mercaptobenzothiazole alone. Of these, eight show little or no scorch. The presence in t h e substituent
of the groups CO-, -NH-, -NOz, -OH, -S-, or -C1 seems to favor subsequent activation. On t h e other hand, certain combinations such as -CH2CO-NH-, -CH2*CO*O-, CaHb*CH2-, CloH,.CH2-, and aliphatic hydrocarbon chains tend to give compounds which are nonaccelerators. The effect of a given group varies not only according t o its position b u t also to t h e other groups present: nevertheless certain group tendencies are manifested.
I T H I X the past few years much progress has been of these materials exhibit the desired curing action when used made in the development of rubber vulcanization alone; some are activated more or less by diphenylguanidine; accelerators of the semi-ultra type which exhibit others remain unaffected. Primarily, the compounds of no prevulcanization or scorch during the preliminary processinterest are those which alone or activated are stronger ing. Most of the commercially important members of this but less scorchy accelerators than mercaptobenzothiazole. class are derivatives of mercaptobenzothiazole in which the However, certain ones which are strongly activated by hydrogen atom of the mercapto group is replaced by an diphenylguanidine and thereby show a moderate scorching organic substituent. The increasing use of these products tendency should not be overlooked since in many cases i t is can be attributed to their possible to eliminate prevulfavorable curing characteristics Eanization by substituting a reBase Stoch Material Added tarding activator such as diand to the valuable physical A =&ctlerotor'h'- 0.15 phenylguanidine phthalate. It properties which they impart to Rubber /o 0 the cured stock. Naunton and Zinc Oxide 5 B s II II 'BS"-0.75 is also recognized that a comSulfur s his eo-workers (4), Twiss and " "cro.75 plete compounding study is D: ' I "0"- 0.75 stearic Acid a5 Jones (8), and Shepard (6)disnecessary for the proper evaluacussed .a' number o'f these. comtion of any accelerator. Plastometer Readinas 700% Modulus of Cures at 134%. in at mm. at 93 'c.pounds in recent papers. NuExperimental Procedure merous references to their preparation and use also appear in the I n order to obtain a furst appatent literature (1,9, 3,5,?',10). proximation of the vulcanizaThe purpose of this paper is to tion characteristics and possi500 determine the effect of various bilities of these materials, they substituents upon the curing were compared alone and acvalue and scorching tendency of tivated by diphenylguanidine, 140 240 360 mercaptobenzothiazole conusing mercaptobenzothiazole *densation derivatives. Few FIUUREI as a control. The general test
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