Hydrolysis with ammonia vapor

For most crops, other than rice, urea in the soil must first undergo hydrolysis to ammonia and then nitrification to nitrate before it can be absorbed by plant roots. One problem is that in relatively cool climates these processes are slow thus plants may be slow to respond to urea fertilization. Another problem, more likely in warmer climates, is that ammonia formed in the soil hydrolysis step may be lost as vapor. This problem is particularly likely when surface appHcation is used, but can be avoided by incorporation of the urea under the soil surface. Another problem that has been encountered with urea is phytotoxicity, the poisoning of seed by contact with the ammonia released during urea hydrolysis in the soil. Placement of urea away from the seed is a solution to this problem. In view of the growing popularity of urea, it appears that its favorable characteristics outweigh the extra care requited in its use. 

Analogously, colloidal tin(lV) oxide with particles of 1-2 (xm in diameter was obtained by the interaction of SnCl4 droplets with water vapor, which required considerably lower temperatures (—15 to -30°C) (62). To promote the rate of hydrolysis at these temperatures, a small amount of ammonia was added into the gas stream. The original amorphous particles started to crystallize into cassiterite on calcination at 400°C, and they retained their sphericity at treatments up to 1000°C. 

Augugliaro et al. have also studied the photoreduction of nitrogen by water vapor in a fixed-bed flow reactor [67]. The putative catalysts were prepared by coprecipitation or by impregnation. Undoped Ti02 was prepared by hydrolysis of aqueous TiCl3 with aqueous ammonia (25 wt %). The resulting precipitate was washed repeatedly with distilled water to remove... 

Properties Wh. or colorless cryst. solid dec. by water into AI(OH)3 and NH3 ammonia odor in moist air m.w. 40.99 dens. 3.10 m.p. 2150 C b.p. dec. 2773 K Mohs hardness 9-10 Toxicology ACGIH TLV 10 mg/m a poison overexposure may cause skin irritation, burning of eyes chronic inh. of dust may cause lung disorders/disease ingestion may release ammonia gas TSCA listed Precaution Incompat. with water and water vapor high humidity or exposure to moisture causes slow hydrolysis and formation of ammonia... 

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