Solid Urea Research Articles

Urease Activity of Enterobacteriaceae: Which Medium to Choose

Detection and intensity of urease activity in enterobacteriaceae greatly varies as a function of the media or techniques used, or both. A comparative investigation on several solid and liquid media led us to the following conclusions. (i) Detection of Proteus spp. can be adequately performed with the highly selective solid medium described by Cook (1948), as well as with the different liquid media described (Stuart standard and rapid media; Elek medium). (ii) Detection of Klebsiella should be based upon urease production on solid media with low buffer capacity (Christensen, 1946). (iii) For the identification of Yersinia, either the solid Christensen urea agar or the rapid Elek technique give optimal results.

Electron spin resonance and CNDO/2 study of the radicals produced during fast electron irradiation of substances containing nitrogen. Part 1.—Formamide, urea, biuret and thiourea

A detailed study has been made of a radical observed during electron irradiation of solid formamide, urea and biuret. Measurements of the 13C hyperfine coupling tensor and of the g-value tensor, in conjunction with CNDO/2 molecular orbital calculations, strongly support its identification as OĊNH2.

Studies on the Syntheses of Mercaptans. V.

The purification of mercaptans prepared from α-olefins and hydrogen sulfide by urea-adduction was investigated. Because α-olefin contains its isomers, the mercaptans prepared by radical addition of hydrogen sulfide to α-olefins are the mixture of straight-chain n-alkylmercaptans and their branched-chain isomers. As a result, it was found that the best method for separation of n-alkylmercaptans from these mixtures was the urea-adduction by reaction of solid urea with mercaptans dissolved in toluene containing a small amount of methanol.In various experimental conditions, the separations were carried out selectively, and the purified mercaptans contained over 98% of n-C10 or n-C12 mercaptan independently of the yields. The yields of n-alkylmercaptans were markedly dependent on the temperature of adduct-formation and on the solvent for the decomposition of urea-adduct. And it was suggested that the mercaptan itself might be an activator for the adduct-formation.In the case of this experimental condition, urea-adduct seemed to be not formed over 40°C and the urea-adduct of n-C8 mercaptan was hardly formed. And over the temperature range from -10°C to 30°C the rate of adduct-formation was accelerated almost linearly with lowering of temperature.The ratios of urea (moles) to the number of carbon atoms of n-mercaptans in the urea-adducts were not constant and decreased with increase of the number of carbon atoms of n-mercaptans from C8 to C18. This probably reflects the steric and polar effects of SH groups of n-mercaptans.Moreover, it was found that the formation of urea-adduct could be identified by IR spectrum. And it was qualitatively confirmed by NMR and mass spectra that the branched-chain isomers of n-mercaptans were derived from those of α-olefins.

Pressure Dependence of Liquid-Solid Ablation Rate

Abstract This investigation relates to the study of reactions between liquid and solid phases. This report describes the study of the influence of pressure on the rate of ablation of solid urea by liquid nitric acid in the range of 1-30 bars. The experimental results obtained are first given, followed by an attempt at interpretation by introducing a relation between pressure and the temperature at the reaction interface and by postulating the existence of an adsorbed layer on the surface of the solid. Three distinct ablation patterns have been uncovered, one at low flow rates where the ablation rate is independent of pressure and is a function of flow only; one at high flow rates where the ablation rate is independent of flow, is a function of pressure only and becomes constant at high pressures; and an intermediate pattern where the ablation rate is a function both of flow and pressure. The results obtained are exactly analogous to those noted in gas-solid ablation, which makes it possible to extend the ...

TOXICITY AS A CAUSE OF THE INEFFICIENCY OF UREA AS A FERTILIZER. I. REVIEW

SummaryThe causes and mechanisms of phytotoxicity that can bring about poor or adverse crop responses to applications of solid urea to soil are reviewed. Compounds which may cause phytotoxicity are urea, transformation products of urea formed during manufacture (biuret), and transformation products produced in the soil or in plants (cyanate, carbamate, ammonia, and nitrite). Of these, ammonia and nitrite are considered to be the most likely causes of phytotoxicity when urea of low biuret content is used.

Adducts of Urea and Thiourea obtained by means of a Sublimation Technique

THE classical methods for obtaining adducts of urea and thiourea with some classes of organic substances imply the use of aqueous or alcoholic solutions of ‘reagents’ (urea or thiourea). Other methods have been described more recently by which adduction is obtained by mixing solid urea directly with the proper ‘reactant’1.

Molecular association complexes of polymers. Urea and thiourea complexes of high molecular weight poly(ethylene oxide)

AbstractComplexes have been formed by mixing urea or thiourea with high molecular weight yoly(ethylene oxide) on a hot roll mill and by precipitation of the complex from benzene solution. The most dramatic method of complex formation, however, is observed when finely divided urea or thiourea is suspended in a benzene solution of poly(ethylene oxide). The complex forms quantitatively, abstracting all the polymer from solution. The rate of complex formation from solid urea or thiourea and poly(ethylene oxide) in solution has been observed, the thiourea complex forming more rapidly than that of urea. This process of formation can be followed by microscopic examination of the suspended urea particles. The crystalline complex appears to form in a ratio of 2 moles of urea or thiourea to 1 mole of oxyethylene monomer unit. The urea complex melts at 143°C. in comparison with the melting point of urea, 132°C., and of poly(ethylene oxide), 65°C. The complex with either urea or thiourea shows distinct x‐ray diffraction patterns, and the presence of complex in a poly(ethylene oxide) matrix can be detected both by x‐ray diffraction and by stiffness–temperature measurements. Both complexes are water‐soluble.

Urea Extraction Methods. IV.

There are several kinds of urea dewaxing process applicable to petroleum fractions. If the recovery of urea from adducts could be simplified, the dewaxing process by solid urea is interesting. Thus, we investigated the solvent extraction of component hydrocarbons from adducts to decide whether this technique is effective or not for applying the continuous dewaxing operation.Toluene was used as the extracting solvent, and extracted at 95°C. Then, we re-used the recovered urea to form urea adduct. The extracting efficiency was not satisfactory. Furthermore, hydrocarbons which have stronger affinity to urea were gradually accumulated. Consequently, subsequent urea adduction was gradually reduced, and inhibitive substances were gradually accumulated in both of recovered solvent and urea.With the experimental results, we understand that this process is not suitable.

Ammonia‐Salt Systems as Nitrogenous Fertilizers

Abstract“Divers' solution” (an NH4NO3‐NH3 system); similar systems of NaI‐NH3, NH4I‐NH3, NaSCN‐NH3, NH4SCN‐NH3, NH4Br‐NH3; and three solid nitrogenous fertilizers (NH4NO3, CO(NH2)2, and urea‐form) were compared in the greenhouse as sources of nitrogen for wheat and millet plants.The systems of NaSCN‐NH3, NH4SCN‐NH3, NH4I‐NH3, and NaI‐NH3 were very toxic for the first crop of plants. Lethal effects of NaSCN‐NH3 and NH4SCN‐NH3 disappeared in about 5 months. Both systems, NH4I‐NH3 and NaI‐NH3, were toxic for a longer period. Applications of NH4Br‐NH3 caused considerable wilting at first but no lethal effects occurred.The greatest nitrogen percentage in wheat plants occurred from use of NH4Br‐NH3 but the greatest total accumulation in plants resulted from use of NH4NO3‐NH3. Urea‐form was ineffective as a source of nitrogen for the first crop. Solid ammonium nitrate and urea were of about the same effectiveness.Herbicidal possibilities for some of the systems were suggested.

STUDIES OF THE MECHANISM OF THE FORMATION AND DECOMPOSITION OF THE MOLECULAR COMPLEX BETWEEN SOLID UREA AND n-OCTANE VAPOR

The formation and decomposition of the molecular complex between solid urea and n-octane vapor, in the presence and absence of initiators, has been studied by a variety of techniques. Suggestions are made for the possible mechanism of this heterophase reaction incorporating known structural and thermodynamic data.

Unsaturated fatty acids. I. Low temperature urea complexes of polyunsaturated acids from bovine tissue

SummaryA mixture of fatty acids obtained from autolyzed saline extracts of beef testicular tissue was fractionated by crystallization of the urea complexes at 5°, −20°, and −75°C. Fractions rich in docosahexaenoic and in arachidonic acids were obtained as solid complexes. The filtrate remaining after precipitation of the solid urea complexes contained a high percentage of hexaenoic acid of shorter chain length than docosahexaenoic, probably eicosahexaenoic acid.

A specific tubercle antigen, extracted from living Myco. tuberculosis

1. 1. Extraction of living cultures of virulent Myco. tuberculosis with solid urea results in the production of a complex mixture of proteins, polysaccharide and nucleic acid. 2. 2. The crude mixture has the biological properties of an unheated tuberculin and reacts in the complement fixation test with the sera of tuberculous humans. 3. 3. By various methods of fractionation a main protein component representing 60–70% of the total extract has been isolated. This main component still contains a small amount of nucleic acid and polysaccharide. Attempts to purify it further have failed. 4. 4. The biological properties of the crude extract are all possessed by the purified protein.