Urea, or urea, is full the amide of the acid carbamino. As a chemical compound urea was discovered in 1773. And. Rollem.

Pure urea is a colorless crystalline substance, odorless, the crystals which have the form of long needles or rhombic prisms. Commercially available product can be slightly colored in yellowish or pinkish color, due to the presence of impurities, in particular iron salts.

Pure urea contains 46.6% nitrogen.

Urea is highly soluble in water, alcohol, and ammonia. With increasing temperature the solubility of urea in water increases. Above 120⁰Since in aqueous solution urea is decomposed into ammonia and carbon dioxide.

Urea has the properties of weak bases. The solubility of urea in liquid ammonia is very high. At temperatures below 46⁰With urea it forms with liquid ammonia complex compound WITH(NH₂)₂*NH₃ (22.1% N).

When heated, aqueous solutions of urea above 80⁰With its intensive hydrolysis and urea is converted into ammonium carbamate

WITH(NH₂)₂ +N₂ABOUT " NH₂ –CO –ARF_4, (2.4.1)

which, in turn, further decomposes into ammonia and carbon dioxide

NH₂ –CO – ARF₄ "2NН₃ +WITH₂ (2.4.2)

At lower temperatures the hydrolysis of urea proceeds with negligible speed. In the case of heating of aqueous solutions of urea, simultaneously with hydrolysis occurs thermal decomposition of urea to form biuret and ammonia

2N₂N – CO – NH₂ ®N₂N- - NH – CO – NH₂ + NH₃ (2.4.3)

With formaldehyde urea interacts, giving a variety of high-molecular compounds. By polycondensation of urea with formaldehyde in an acidic medium are specific nitrogen fertilizer, slowly giving nitrogen. They treat concentrated nitrogen fertilizer, unnecessarily. contain up to 40% nitrogen.

In n in. available two varieties of urea: crystalline and granular.

Crystalline urea, basically, designed for technical needs, granular is mainly used as fertilizer and nitrogen-containing additive to fodder for cattle.

Application

Urea (urea) among nitrogen fertilizer ranks second in production after ammonium nitrate. Increased production of urea due to the wide scope of its application in agriculture. It has a higher resistance to leaching compared to other nitrogen fertilizers, ie. less susceptible to leaching from the soil.

Urea, containing up to 46.5% nitrogen, is a concentrated ballastless fertilizer. Nitrogen urea is easily assimilated by the plants. As a fertilizer, urea has advantages over ammonium nitrate is not explosive it, less hygroscopic and not so much compressed. The hygroscopic point of urea at 20⁰With equal 80%. However, the price of nitrogen in urea is slightly more of its value in ammonium nitrate.

In the soil urea under the action of moisture at first is converted into ammonium carbonate, providing a neutralizing effect on acidic soil. But further ammonium ion nitrificants, which leads to the acidification of soil. Therefore, the urea should be attributed to the fertilizer with a little saline acidity.

A harmful impurity in urea is biuret. If its content is greater than 0.25%, when foliar feeding of plants with urea solution may burn the leaves.

Urea, in addition, widely used for obtaining complex fertilizers, fertilizers with adjustable expiration time.

Urea is used for feeding ruminants. It is added to the feed, contains a lot of carbohydrates and little protein.

In industry, urea is used for making varnishes, synthetic resins, plastics, adhesives, pharmaceuticals. Large quantity of urea used in the manufacture of urea-formaldehyde polymers, it is obtained from melamine, used for the production of melamine-formaldehyde resins.

Raw