Amount Of Ammonium Sulfate Research Articles

Modeling and experimental studies on chemical absorption of ammonia emitted from poultry manure during the drying process by a wet spray scrubber: Optimization by Box-Behnken design

One of the most important environmental worries related to poultry production is ammonia gas emission which is affected by poultry manure moisture. This research was aimed at investigating poultry manure drying in a hot air dryer and its influence on ammonium nitrogen losses to provide an overview of ammonia gas emissions and absorption of emitted ammonia by a spray scrubber. The effect of air temperature (60–80 °C), air relative humidity (8–18 %), manure depth (2–4 cm), and air velocity (2–3 m s−1) were analyzed to optimize the drying process. The optimization of ammonia absorption involved analyzing the effects of absorbent solution temperature (30–50 °C), solution pH (2−4), and nozzle operating pressure (0.2–0.6 Mpa). The Box–Behnken design was applied to optimize these processes. Manure depth was the factor that had the most significant effect on both drying duration and ammonia emission (ammonium nitrogen losses). during the drying process, the ammonium nitrogen losses increased with increasing the manure depth and decreasing the air velocity and air temperature. The optimum ammonium nitrogen was 570,330 mg h lit−1 at an air temperature of 60 °C, air relative humidity of 8.11 %, manure depth of 3.95 cm, and air velocity of 2 m s−1. Both the temperature of the absorbent solution and the solution pH had opposite effects on the ammonia absorption. Increasing nozzle operating pressure increased ammonia absorption. The maximum ammonia absorption was obtained at a solution temperature of 49.2 °C, solution pH of 2, and nozzle operating pressure of 0.58 Mpa. At these conditions, the amount of ammonium sulfate in the absorbent solution was 9.09 g lit−1 and the efficiency of the spray scrubber was 66.79 %. So, we can be sure that ammonia emission from poultry manure and the absorption of emitted ammonia can be controlled by varying the investigated variables.

Effects of nitrogen application level on the physiological characteristics, yield and fruit quality of blackberry

To study the optimal amount of nitrogen application for blackberry plants, different amounts of ammonium sulfate were applied to three-year-old healthy ‘Shuofeng’ blackberry plants at three key growth stages (early bud burst, the flowering stage and the fruit veraison stage) to explore the effects of nitrogen fertilizer application level on the physiological characteristics of leaves, yield and fruit quality of blackberry. Overall, the leaves turned yellow, and cellular metabolism was disrupted in the CK group (no nitrogen fertilization). Among the nitrogen treatments, the leaf chlorophyll content, photosynthesis efficiency and antioxidant enzyme activity were significantly higher under the T2 (40 g plant−1) and T3 (60 g plant−1) treatments than under the T1 (20 g plant−1) and T4 (80 g plant−1) treatments, while the contents of ascorbic acid, glutathione, hydrogen peroxide and malondialdehyde showed the opposite trends. The yield, single-fruit weight, solids–acids ratio and anthocyanin contents of blackberry fruits increased first and then decreased with increasing nitrogen application. The contents of polyphenols and ellagic acid in fruits decreased with increasing nitrogen application. Correlation and principal component analysis showed that yield and its components were closely related to leaf photosynthesis characteristics and the antioxidant system (P<0.05). Application of 20 g ammonium sulfate per plant at early bud burst, the flowering stage and the fruit veraison stage was profitable, which resulted in more vigorously growth, increased yield and fruit quality, while the production cost was the most economical because of the low fertilizer consumption.

Optimization of baker`s yeast production on grape juice using response surface methodology

There is an increasing interest in improving biological processes, including fermentation processes, improving fermentation conditions is difficult, as it requires the use of an appropriate improvement method that allows operating the biological fermenter under optimal conditions in order to obtain the largest possible amount of the final product. The aim of this work was to succeed in examples of fermentation conditions to produce the largest possible quantity of dry yeast biomass Saccharomyces cerevisiae using grape juice as the sole carbon source. The optimum values of five factors that have an effect on the production of dry biomass from baker`s yeast were determined. The design of the experiments was carried out using the central composite experimental design (CCD) and the number of experiments according to the design was (54) experiments, the response surface methodology method was used to determine the best possible amount of production of yeast, and has reached (41.44 g/L) after 12 hours of fermentation, under the following optimal conditions (temperature (30.11??), pH (4.75), sugar concentration (158.36 g/L), the ratio of carbon to nitrogen (an essential nutrient for yeast growth ) is (11.9), initial concentration of yeasts (2.5 g/L), the amount of urea was 6.65 g/L and the amount of ammonium sulfate used was 6.65 g/L, so that the concentration of added urea and ammonium sulfate was (50-50)% and the required C/N ratio was achieved, and the used agitation speed was equal to 200 r.p.m during the fermentation process. The fermenter power of the obtained yeast was 470 ml. Three kinematic models (Monod, Verhulst, and Tessier) were also selected for the purpose of studying the kinetic performance of Saccharomyces cerevisiae yeast. Monod and Tessier`s models did not give satisfactory results, while the best results were according to the Verhulst model. Also, the Leudeking Piret model has also been successfully used to predict substrate consumption during fermentation time.

High Resistance of SO2 and H2O over Monolithic Mn-Fe-Ce-Al-O Catalyst for Low Temperature NH3-SCR

Monolithic Mn-Fe-Ce-Al-O catalyst with honeycomb cordierite ceramic as a carrier was reported for the first time for low temperature deNOx application. In the reaction of selective catalytic reduction (SCR) of NO with NH3, a NO conversion of above 80% at 100 °C was obtained. Notably, the catalyst also showed excellent resistance against SO2 and H2O. About 60% NO conversion was maintained after successive operation in the mixed stream of SO2 and H2O for 168 h. The Brunner−Emmet−Teller (BET) measurement, SEM, EDS, thermogravimetric analysis (TG), FT-IR, and XPS results of the used catalysts indicated that certain amounts of ammonium sulfate was formed on the surface of the catalyst. XPS results revealed that partial of Fe2+ was oxidized to Fe3+ during the reaction process, and Fe2+ species have strong redox ability, which can explain the decrease in activity after reaction. In addition, SO2 and H2O induced a transformation of Ce from Ce4+ to Ce3+ on the surface of the catalyst, which increased the amount of chemisorbed oxygen. Owing to these factors, the addition of Ce and Fe species contributes to excellent resistance of the catalyst to SO2 and H2O.

Effect of inorganic-to-organic mass ratio on the heterogeneous OH reaction rates of erythritol: implications for atmospheric chemical stability of 2-methyltetrols

Abstract. The 2-methyltetrols have been widely chosen as chemical tracers for isoprene-derived secondary organic aerosols. While they are often assumed to be relatively unreactive, a laboratory study reported that pure erythritol particles (an analog of 2-methyltetrols) can be heterogeneously oxidized by gas-phase OH radicals at a significant rate. This might question the efficacy of these compounds as tracers in aerosol source-apportionment studies. Additional uncertainty could arise as organic compounds and inorganic salts often coexist in atmospheric particles. To gain more insights into the chemical stability of 2-methyltetrols in atmospheric particles, this study investigates the heterogeneous OH oxidation of pure erythritol particles and particles containing erythritol and ammonium sulfate (AS) at different dry inorganic-to-organic mass ratios (IOR) in an aerosol flow tube reactor at a high relative humidity of 85 %. The same reaction products are formed upon heterogenous OH oxidation of erythritol and erythritol–AS particles, suggesting that the reaction pathways are not strongly affected by the presence and amount of AS. On the other hand, the effective OH uptake coefficient, γeff, is found to decrease by about a factor of ∼20 from 0.45±0.025 to 0.02±0.001 when the relative abundance of AS increases and the IOR increases from 0.0 to 5.0. One likely explanation is the presence of dissolved ions slows down the reaction rates by decreasing the surface concentration of erythritol and reducing the frequency of collision between erythritol and gas-phase OH radicals at the particle surface. Hence, the heterogeneous OH reactivity of erythritol and likely 2-methyltetrols in atmospheric particles would be slower than previously thought when the salts are present. Given 2-methyltetrols often coexist with a significant amount of AS in many environments, where ambient IOR can vary from ∼1.89 to ∼250, our kinetic data would suggest that 2-methyltetrols in atmospheric particles are likely chemically stable against heterogeneous OH oxidation under humid conditions.

Purification of phycocyanin from Arthrospira platensis by hydrophobic interaction membrane chromatography

The cyanobacterium Arthrospira platensis is an important source of phycocyanin, which has many commercial applications in foods, cosmetics and pharmaceutics. In this study, hydrophobic interaction membrane chromatography (HIMC) was used for the first time to separate phycocyanin from allophycocyanin and obtain analytical grade phycocyanin, avoiding packed bed (i.e., packed column) chromatography steps. The extraction of phycobiliproteins was carried out on freeze-dried biomass samples suspended in NaCl 0.1 M, and the phycobiliprotein crude extract was obtained by centrifuging the suspension to eliminate cell debris. The crude extract, after the addition of an appropriate amount of ammonium sulphate, was loaded on an ammonium sulphate responsive commercial hydrophilic polyvinylidene fluoride (PVDF) membrane for the HIMC purification process. Applying a two-step HIMC purification procedure, a phycocyanin purity ratio of 4.20 and a yield of 67.0% was attained.

Extraction of Limonin in Lemon Peel by Ultrasonic-assisted Aqueous Two-phase System

In this study,limonin was extracted from dried lemon peel by ultrasonic-assisted aqueous two-phase system of ethanol-( NH4)2SO4. The effects of ethanol concentration,solid-liquid ratio,amount of ammonium sulfate,ultrasonic treatment temperature,ultrasonic treatment time,extraction temperature and extraction time,on the extraction yield,were studied by the single factor experiments and orthogonal tests. The results showed that when the volume concentration of alcohol was 60%,the solid-liquid ratio was 1∶ 20 g / m L,the amount of ammonium sulfate was 12 g,the treatment temperature was 60 ℃,the ultrasonic treatment time was 30 min,the extraction temperature was 50 ℃ and the extraction time was 3 h,the extraction yield of limonin reached the maximum. Under the optimal conditions,three parallel experiments were carried out and the average extraction yield reached 0. 3222%. The reproducibility of the optimized method was good.

Estudo das metodologias de destilação na quantificação do Nitrogênio das Bases Voláteis Totais em pescada, tilápia e camarão

O pescado apresenta grande importância no panorama atual e a manutenção da sua qualidade e inocuidade é imprescindível para se obter alimento seguro. Por ser um alimento altamente perecível, o pescado necessita de cuidados em todas as etapas da cadeia produtiva. Um dos métodos utilizados mundialmente para avaliar a qualidade do pescado é a determinação do Nitrogênio das Bases Voláteis Totais (N-BVT), que consiste na quantificação de compostos de baixo peso molecular, como a trimetilamina, dimetilamina e amônia, que são formados durante o processo de deterioração do pescado. O objetivo deste trabalho foi avaliar a eficiência de duas metodologias de quantificação de N-BVT (BRASIL 1981 e BRASIL 1999) por destilação, para três espécies de pescado de importância comercial, assim como buscar a diminuição do volume de amostras e reagentes utilizados. Para verificar a eficiência das metodologias utilizou-se um índice de recuperação, adicionando-se quantidades conhecidas de sulfato de amônio [(NH4)2SO4] nas amostras e comparando-se o teor de N-BVT recuperado com uma amostra controle. Foram testadas modificações na metodologia BRASIL 1999 quanto à redução nas quantidades de amostra e reagente. Considerando-se o desempenho quanto à recuperação do nitrogênio adicionado às amostras, os resultados demostraram que não houve diferença quanto à recuperação de nitrogênio nos dois métodos (BRASIL 1981 e BRASIL 1999) para as três espécies estudadas, evidenciando-se que ambos podem ser empregados com a mesma eficiência. Os resultados indicam que a redução na quantidade de amostra e reagentes, nas determinações de N-BVT para o método BRASIL 1999, pode interferir significativamente nos resultados.

Influence of Solution Parameters on Phase Diagram of Recombinant Spider Silk-Like Block Copolymers

Spider silks form interesting protein-based materials with exceptional mechanical properties from processing in aqueous systems. To more fully understand the role of specific chemical domains in the proteins responsible for these material features, selective regions are utilized to assess structure–function relationships. Toward this goal, the amphiphilic spider silk-like block copolymer HBA6 [hexahistidine tag (H), with hydrophilic (B) and hydrophobic (A) blocks] is studied to generate a partial phase diagram of the morphologies formed under different processing environments. Particles of HBA6 are prepared from a 2 m phosphate buffer at pH 5 and 8, and the resultant phase behavior upon ammonium sulfate (AS) addition is examined at room temperature for protein concentrations from 0.1 to 17 wt%. There is no apparent difference in the sizes of the microspheres formed at pH 8, irrespective of the amount of AS. In contrast, mixed morphologies ranging from unordered structures to clustered sheets to nanofibril-like morphologies are obtained at pH 5 with varying concentrations of AS. A partial ternary phase diagram is reported, representing the different morphologies obtained by changing the concentrations of HBA6, AS, and water. Differences in the morphologies as observed from scanning electron microscopy (SEM) are the result of altered protein-solute, interprotein, and intraprotein interactions caused by changing the pH and AS concentrations. The characteristics of the different morphologies illustrate how material properties based on motifs from spider silks can be tuned towards specific features, an important control point for matching materials to applications.

암모니아 용출용액을 이용한 저 품위 엽납석으로부터 Fe 제거 효율과 용해 동역학

저 품위 엽납석 광석에 포함된 불순물 Fe를 제거하기 위하여 입도크기, 황산농도, 황산암모늄농도, 과산화수소농도 그리고 온도변화에 따른 제거 효율에 대하여 연구하였다. 저 품위 엽납석 광석에서 자형의 입방체 황철석이 포함된 것을 반사현미경으로 관찰할 수 있었으며, X-선 회절분석결과 주 구성광물은 석영과 딕카이트였다. 실험 결과 Fe 용출율이 최대로 나타나는 입도 -325 mesh에서, 황산농도는 2.0 M에서, 황산암모늄 농도는 10.0 g/l, 과산화수소 농도 3.0 M 그리고 최적의 용출 온도는 <TEX>$70^{\circ}C$</TEX>에서였다. 용해 동역학 분석에서, Fe 용해는 황철석 표면에서 일어나며 화학적 반응에 통제되는 것으로 그리고 0.066/R, <TEX>$[H_2SO_4</TEX><TEX>]</TEX><TEX>^{1.156}$</TEX>, <TEX>$[(NH_4)_2SO_4</TEX><TEX>]</TEX><TEX>^{0.745}$</TEX>, <TEX>$[H_2O_2</TEX><TEX>]</TEX><TEX>^{0.428}$</TEX>에 비례하는 것으로 나타났다. In order to remove Fe impurity from low-grade pyrophyllite ore, the effect of certain variables such as particle size, concentration of sulfuric acid, amount of ammonium sulfate, added hydrogen peroxide, and temperature were studied. The euhedral cubic pyrites were observed in the low-grade pyrophyllite ore by reflected light microscopy, and quartz and dickite were identified in the sample by XRD analysis. The results of the Fe removal experiments showed that the best Fe removal parameters were when the particle size was at -325 mesh, the addition of <TEX>$H_2SO_4$</TEX>, <TEX>$(NH_4)_2SO_4$</TEX> and <TEX>$H_2O_2$</TEX> was at a 2.0 M, 10.0 g/l, and 3.0 M concentration, respectively, and at a <TEX>$70^{\circ}C$</TEX> leaching temperature. In the dissolution kinetics analysis, the dissolution of Fe from the pyrite surface was a controlled chemical reaction, and the Fe dissolution reaction was proportioned to 0.066/R, <TEX>$[H_2SO_4</TEX><TEX>]</TEX><TEX>^{1.156}$</TEX>, <TEX>$[(NH_4)_2SO_4</TEX><TEX>]</TEX><TEX>^{0.745}$</TEX>, <TEX>$[H_2O_2</TEX><TEX>]</TEX><TEX>^{0.428}$</TEX>.

Synthesis of Ultrafine Spherical Yttrium Aluminum Garnet Powders from Yttrium Nitrate and Aluminum Nitrate System

Ultrafine spherical yttrium aluminum garnet (YAG) powders have been synthesized via homogeneous precipitation method using urea as the precipitant. The precursor powders were calcinated at 1000°C or 1100°C for 4 hrs and then were studied by means of FE-SEM, XRD, FT-IR and TG-DTA. The result shows that the amount of ammonium sulfate has a significant effect on morphology and particle size of powders. Pure phase and spherical YAG particles with 350 nm in diameter can be obtained when the molar ratio of ammonium sulfate to aluminum nitrate is about 0.75 and the concentration of the metallic ions is 0.008M.

Synthesis of Uniform Spherical Alumina Powders by Homogeneous Precipitation

Uniform spherical alumina powders have been synthesized via homogeneous precipitation method from aluminum nitrate using urea as the precipitant. The amount of ammonium sulfate has a significant effect on morphology and particle size of the precursor powders. It was found that spherical particles can be obtained when the molar ratio of ammonium sulfate to aluminum nitrate is about 0.72 and the concentration of the aluminum nitrate is 0.005M. Spherical alumina particles with 400 nm in diameter were obtained by calcining the precursors at 1100°C for 4 hrs.

Glyphosate Weed Control Enhancement with Ammonium Sulfate and Commercial Water Conditioning Agents

Abstract Glyphosate herbicide labels generally recommend addition of ammonium sulfate (AMS) to the spray solution, which often improves weed control, especially when mixed with hard water. AMS in solution disassociates, and the sulfate binds with cations in the spray solution, preventing the development of glyphosate-cation complexes that tend to have lower absorption into plant leaves. In addition, the ammonium ion can associate with the glyphosate molecule, which helps facilitate glyphosate absorption into the leaf. The recommended AMS rate is 1–2 % w/w, and AMS is available in both dry and liquid formulations. Applicators generally find AMS inconvenient to use because of the high use rate and handling issues. Several companies are marketing low-rate water conditioner products to be used as an alternative to AMS with glyphosate. Pesticide applicators like the convenience of low-rate water conditioners, but performance of these products has been inconsistent. Field experiments were conducted near Manhattan, KS, from 2005 to 2008 to compare the efficacy of glyphosate with AMS and various commercial water conditioners on velvetleaf, sorghum, corn, and sunflower. Each experiment consisted of a sublethal (0.31 or 0.43 kg ae/ha) dose of glyphosate applied in combination with the recommended application rate of each adjuvant. Water hardness, environmental conditions, and plant growth stages varied by experiment. Control of all assay species with glyphosate was enhanced by the addition of AMS, unless control was near complete in the absence of AMS. Commercial water conditioner products that included an AMS component at the equivalent rate of 1 % w/w gave equal or slightly better control than glyphosate plus 1 % w/w AMS. Commercial water conditioners that did not provide an equivalent amount of AMS gave less control than glyphosate with 1 % or 2 % w/w AMS and were often no better than glyphosate alone for the low-rate products.

Manipulation of N,O-Nucleophilicity: Efficient Formation of 4-N-Substituted 2,4-Dihydro-3H-1,2,4-Triazolin-3-ones

A new efficient two-step synthesis of 2,4-dihydro-3H-1,2,4-triazolin-3-ones (triazolinones) from readily available amines is reported. Our novel conditions using hexamethyl disilazane, bromotrimethylsilane, and a catalytic amount of ammonium sulfate smoothly cyclize 1-formyl and 1-acetyl semicarbazides to the target triazolinones. This transformation features simultaneous manipulation of N- and O-nucleophilicity as well as differentiation of the nucleophilicity of a urea and an acyl carbonyl.

Macroaffinity ligand-facilitated three-phase partitioning for purification of glucoamylase and pullulanase using alginate

Starch-degrading enzymes glucoamylase (from Aspergillus niger), and pullulanase (from Bacillus acidopullulyticus) were purified using alginates (polysaccharides consisting of mannuronic acids and guluronic acids) by a recently developed technique called macroaffinity ligand-facilitated three-phase partitioning (MLFTPP). In this process, a crude preparation of the enzyme was mixed with alginate. On addition of appropriate amounts of ammonium sulfate and t-butanol, the alginate bound enzyme appeared as an interfacial precipitate between the lower aqueous and the upper t-butanol phase. Enzyme activity from this interfacial precipitate was recovered using 1 M maltose. Glucoamylase and pullulanase were purified 20- and 38-fold with 83% and 89% activity recovery, respectively. Both the purified preparations showed a single band on SDS–PAGE.

Effect of Roasting with Ammonium Sulfate and Sulfuric Acid on the Extraction of Copper and Cobalt from Copper Converter Slag

Abstract Copper converter slag, provided by Ergani Copper Co. of Etibank and containing 2.56% copper and 0.22% cobalt, was roasted with ammonium sulfate. The effects of such parameters as temperature (200–600°C), duration of roasting (15–120 min), and amount of ammonium sulfate (0.5–2.5 times stoichiometric) have been studied. Under optimum conditions (slag size, − 100 mesh; stoichiometric requirement of ammonium sulfate; roasting temperature of 400°C for 60 min), we obtained 88% Cu and 67% Co by extraction. Similar studies were carried out with concentrated sulfuric acid. The influence of experimental variables such as roasting temperature (25–300°C), roasting period (30–120 min), and amount of sulfuric acid (0.5–2 times stoichiometric) has been studied. Under atmospheric conditions, i.e., at 200°C and a roasting period of 60 min with 1.5 times the stoichiometric amount of sulfuric acid, recoveries of copper and cobalt were 82 and 96%, respectively.

Sulphation Kinetics of Zinc Sulphide with Ammonium Sulphate and Ammonium Bisulphate

Studies on the kinetics of sulphation of zinc sulphide with ammonium sulphate have been carried out. The influence of temperature (448 K to 873 K), reaction atmosphere such as oxygen, nitrogen and air, amount of ammonium sulphate up to 330% stoichiometry and duration of roasting (up to 120 min) have been studied.The activation energy values using the Arrhenius equation were 84 and 36 kJ/mol in the temperature ranges of 448 K–548 K and 548 K–623 K respectively indicating two separate reaction mechanisms. To confirm the two reaction mechanisms, similar studies were carried out using ammonium bisulphate in the same temperature range. The activation energy was 42 kJ/mol which agreed well with that obtained in case of ammonium sulphate at higher temperature range studied. The activation energy values based on initial rates were 29 and 17 kJ/mol with ammonium sulphate and ammonium bisulphate respectively. Sulphation increased with addition of ammonium sulphate and ammonium bisulphate, more rapidly with the latter. Sulphation reaction of zinc sulphide with these two reagents were of first order.

Recovery of cobalt, nickel and copper from converter slag through roasting with ammonium sulphate and sulphuric acid

Roasting of copper converter slag containing 4.03% copper, 1.98% nickel and 0.48% cobalt with ammonium sulphate open to atmosphere has been carried out in order to achieve sulphation of copper, nickel and cobalt followed by leaching of the metal values as soluble sulphates with water. The effect of parameters such as temperature (200–600°C), time (15–120 min), and amount of ammonium sulphate (0.5–2.5 times stoichiometric) has been studied. Under atmospheric conditions, using 2.5 times the stoichiometric requirement of ammonium sulphate, the recovery of copper, nickel and cobalt was found to be 85%, 81% and 85%, respectively. Similar studies were carried out with sulphuric acid. The influence of experimental variables such as the amount of sulphuric acid (0.25–2 times stoichiometric), roasting temperature (100–300°C) and time (15–120 min) has been studied. Under optimum conditions, i.e., at 150°C and a roasting time of 60 min with the stoichiometric amount of sulphuric acid, recoveries of copper, nickel and cobalt were 95, 90 and 99%, respectively, along with a contamination of 60–80% iron. Removal of most of the iron from the leach liquors has been effected with ammonia liquor and lime as precipitants. A two-stage roasting operation using sulphuric acid, first at 150°C and then at 650°C, has resulted in bringing the iron content down to about 3% in the sulphation product without much affecting the recovery of other metal values.

Chemical attractants tested against the Australian bush flyMusca vetustissima (Diptera: Muscidae)

A number of chemical compositions known to attract several synanthropic and pest fly species were tested against the Australian bush flyMusca vetustissima, a severe and persistent pest of man and domesticated and wild mammals. A standard composition containing small quantities of trimethylamine and indole, blended with large amounts of ammonium sulfate and anchovy meal, showed good attractancy against this fly. Deletion of ammonium sulfate did not significantly alter attractancy. Similarly, incorporation ofn-butyric acid and linoleic acid into the formulation did not alter attractancy, nor did addition of several carbonates and bicarbonates. Skatole, a closely related compound to indole, decreased attractancy significantly. In all the tests, the attractant compositions lured greater number of females than males. The attractancy of the standard composition was studied and compared with equal amount of fresh cattle dung. Chemical attractants lured bush flies and not dung beetles, while dung attracted both flies and beetles. The dung resource was 4.6 × more attractive to flies than the standard attractant composition. This suggests that there are other chemical attractants emanating from dung that warrant isolation and identification work. Nevertheless, the chemical attractants studied here provide a starting point for further investigations. The ratio of female to male flies attracted to humans was greater than the ratio of flies attracted to chemicals. The sex ratio of flies netted from human host was 3.0, while the sex ratio of flies attracted to chemical attractants was 1.8. The preponderance of females attracted to both sources was probably due to physiological requirements of the sexes.

N,N?-bis(3-trialkoxysilylpropyl)- and N,N?-bis(3-trialkylsilylpropyl)thioureas

The reaction of trialkyl- and trialkoxy(3-aminopropyl)silanes with paraformaldehyde yielded 1,3,5-tris-(3′-trialkylsilylpropyl)- and 1,3,5-tris(3′-trialkoxysilylpropyl)hexahydrotriazines, respectively, which, upon treatment with sulfur, were converted into N,N′-bis(3-trialkylsilylpropyl)- or N,N′-bis(trialkoxysilylpropyl)-thioureas. The same compounds were also obtained by heating trialkyl- or trialkoxy(3-aminopropyl)silanes with thiourea in the presence of catalytic amounts of ammonium sulfate.