• urea, also known as urea or carbamide, is a final product of protein metabolism in humans and mammals, and is also a major organic nitride excreted by animals. The pure product is white granular or needle-like, prismatic crystal, mixed with heavy metals such as iron is reddish or yellow. Taste and odor, soluble in water, ethanol and benzene, insoluble in ether and chloroform. At 20 ℃, 100kg of water can dissolve 105kg of urea and absorb heat when dissolved. The aqueous solution is a neutral reaction. Pure nitrogen content is 46.65, agricultural urea is 42% ~ 46%, containing a small amount of biuret, generally less than 2%, usually harmless to crop growth; The specific gravity and bulk density of urea are small, weighing 0.65 tons per cubic meter of fertilizer.
• when the temperature is below 20 ℃ and the relative humidity is below 70%, urea not only does not absorb moisture, but also evaporates water and reduces its water content. When the temperature exceeds 20 ℃ and the relative humidity is higher than 80%, it starts to absorb moisture. In severe cases, it is pasty. When the air is dried again, it will agglomerate again, which is second only to ammonium nitrate. When the urea aqueous solution is at 80 ℃, hydrolysis and decomposition reactions will occur to form ammonium carbamate, ammonia and carbon dioxide respectively. Under acid and alkaline conditions, when urea is heated, the decomposition is accelerated.
• Urea is easy to combine with linear carbohydrates to form crystalline additional compounds; with a variety of inorganic compounds to form Ca(NO3)2 · 4CO (NH2)2, NH4Cl · CO (NH2)2, CaSO4 · 4CO (NH2)2 · 4CO (NH2)2 · 3H2O, Mg (NO3) · 4CO (NH2)2 · 2H2O and other complex salts; it is easy to form urea phosphate, dicalcium phosphate and water with monocalcium phosphate, namely Ca(H2PO4)2 H2O + CO (NH2)2 → H3PO4 CO (NH2)2 + CaHPO4 + H2O; Urea nitrate, CO (NH2)2 + HNO3 → CO (NH2)2 HNO3, which can be combined with formaldehyde to generate urea formaldehyde compounds (uric acid condensate), among them, the high proportion of formaldehyde is urea resin, and the low proportion is slow-release (effective) urea.

white columnar crystal or crystalline powder. Lg of this product is soluble in 1mL of water, 10mL 95% ethanol, 1mL 95% boiling ethanol, 20mL of anhydrous ethanol, 6mL of methanol and 2mL of glycerol, soluble in concentrated hydrochloric acid, and almost insoluble in ether and chloroform. When heated above the melting point, it decomposes into biuret, ammonia and cyanuric acid.

Ammonia and carbon dioxide react to form ammonium carbamate, which is then dehydrated to form urea.

Pharmaceutical excipients, penetration enhancers, cosolvents.

This product contains CH4N20 not less than 99.5%.

• This product is colorless prismatic crystal or white crystalline powder; almost odorless, taste salty and cool; placed for a long time, gradually faint ammonia odor; aqueous solution showed neutral reaction.
• This product in water or ethanol soluble in ether or three gas methane insoluble.

melting point

The melting point (general 0612) is 132~135 ℃.

• urea is an important nitrogen fertilizer with high quality and high efficiency. At the end of the First World War, Germany began to use urea as fertilizer. Practice has proved that urea has high nitrogen content and no side components, and shows good yield-increasing effect on all crops. After the 1950 s, it became a key nitrogen fertilizer variety developed by various countries. In the 15 years from 1960 to 1975, the global urea production increased by 10.5 times, and gradually replaced ammonium nitrate from the 1970 s to become the most widely used nitrogen fertilizer variety in all countries in the world. After urea is applied to the soil, a small part of it is absorbed by plants in the form of amide. Most of it is ammoniated under the action of urease and converted into ammonia, which is then absorbed by plants. The decomposition rate depends on the soil quality, temperature and water content. Generally in 3 to 10 days, so the fertilizer efficiency of urea is longer than other nitrogen fertilizers and nitrogen loss is less. Urea is an ideal fertilizer for topdressing outside the root, because it does not contain harmful ingredients to crops, is neutral, does not burn stems and leaves, hygroscopic, easy to penetrate into the leaves with water, quickly absorbed by crops. The concentration of topdressing outside the root is generally 0.5 ~ 2%. In order to improve the effect of urea utilization, we must not only correctly grasp the nature and application conditions of urea, but also pay attention to reasonable application.
• Urea is a neutral fertilizer, does not contain harmful components, hydrolysate NH +4 and HCO-3 can be absorbed by crops, applied in successive years, generally no adverse effects on soil properties. It is suitable for all kinds of crops and soil, and its fertilizer effect is similar to that of ammonium sulfate with the same amount of nitrogen. It is better than ammonium sulfate for the "aging" paddy fields that lack active iron and are prone to hydrogen sulfide poisoning. Excessive application of urea or high biuret content is easy to cause ammonia and biuret poisoning to crops; the higher the urease activity of crops, the more sensitive to urea and biuret poisoning.
• urea can be used as a supplementary feed for anti-chick animals. Urea is a raw material for the synthesis of urea-formaldehyde and melamine-formaldehyde resins in industry. Pharmaceutically used in the manufacture of tetracycline, phenobarbital, caffeine and other drugs. The dye industry uses it to produce reduced brown BR, phthalocyanine blue B, etc.
• Urea is packed in woven bags lined with plastic film and jacketed. It shall be stored in a dry warehouse and shall not be mixed with acids.

Examination of antimony and tin, determination of lead, copper, gallium, phosphorus, iodide, nitrate.

1. Take 0.5g of this product, heat it in a test tube, liquefy it and release ammonia gas. Continue to heat until the liquid is turbid, cool, add water 10ml and sodium hydroxide test solution 2ml to dissolve, add copper sulfate test solution 1 drop, that is, purple red.
2. Take 0.1g of this product, add water lml to dissolve, add nitric acid 1ml to generate white crystalline precipitate.
3. The product's infrared absorption map should be consistent with the control's map (spectral set 210 map).

• The application methods of urea include base fertilizer, top dressing, seed fertilizer or root top dressing. The application time of base and top dressing should be 4 to 5 days earlier than ammonium nitrogen fertilizer, and the application rate should be reduced accordingly according to the nitrogen content. Urea is used as a base fertilizer for paddy fields. It should be ploughed immediately after 5 to 7 days before irrigation. Do not irrigate too early after application to reduce the direct loss of urea. When used as top dressing, the water should be drained to the surface of the field to keep the shallow water layer. After fertilization, the field should be cultivated immediately and kept for 2 to 3 days without irrigation. The application method of urea for dry land base fertilizer and top dressing is basically similar to various ammonium nitrogen fertilizers. Urea is generally not directly used as seed fertilizer, because the concentration and pH value of urea or ammonia in the fertilization belt are high, which will lead to protein denaturation, hinder seed germination and seedling growth, and even make seeds lose germination ability, which is especially harmful to small seeds. However, if urea is mixed with dry fine soil before being applied to a certain depth under the seed, and covered with a thin soil layer before sowing; Or apply urea sideways at 2.5cm from the seed, it has no adverse effect on seed germination.
• The speed of urea absorption and utilization of leaves of general crops is faster than that of roots. Urea is better than other nitrogen fertilizers for topdressing outside roots. The reasons are as follows: ① Urea is neutral organic nitrogen and does not contain secondary components. Spraying solution with general concentration has little burning on crop stems and leaves. The ionization degree is very small, the molecular size is also small, easy to enter the leaf cell through the cell membrane. The molecular urea has a higher penetration and diffusion speed, in the penetration of the cell, is not easy to occur the separation of the quality of the wall, even if it occurs, it is easy to recover. The itself has a strong hygroscopicity. The solid urea remaining on the leaf surface due to the evaporation of the spray liquid can still absorb moisture and dissolve again, and the absorption utilization rate is high. The appropriate concentration of urea as external root dressing varies with crop species and their growth stages. The optimum concentration of common rice, wheat and gramineous herbage is 2.0%, cucumber 1.0%~ 1.5%, radish, cabbage, spinach and cabbage 1.0%, watermelon, eggplant, sweet potato, potato, peanut and citrus 0.4%~ 0.8%, mulberry, tea, pear, apple and grape 0.5%, persimmon, tomato, strawberry, greenhouse cucumber and eggplant, flowers for 0.2~0.3. Usually every 7 to 10 days spray once, a total of 2 to 3 times. The dosage of the solution is 750-1125kg per hectare, and the degree is taken as the degree to which the leaves are wet. Spraying time in the early morning or evening is better. The content of biuret in urea used as topdressing for root shall not be higher than 0.5% to avoid leaf injury.