No abstract

No abstract

A study is reported of some of the factors affecting the physical condition of superphosphate made by mixing ground phosphate rock with 70 t o 85 per cent phosphoric acid. The factors investigated were: length of mixing time; composition and particle size of phosphate rock ; strength, temperature, and quantity of acid. Mixtures of phosphoric and sulfuric acids were also used. Some data on the chemical composition of the products plication of the conditions for of concentrated scribed. are included. The apresults in the choice of plant-scale production superphosphate is de- 6, HE plant constructed by the TennesseeValley Authority a t Wilson Dam, Ala., T for the manufacture of concentrated superphosphate has been described by Curtis (2, 3). A brief discussion was included of some of the small-scale experimental work which laid the foundation for the commercial-plant construction.The present paper describes in greater detail some of the research performed in the Chemical Engineering Laboratory of the T. V. A. on the manufacture of concentrated superphosphate (40 to 48 per cent PZOS) from phosphoric acid and ground phosphate rock. The paper is concerned primarily with a study of some of the factors affecting the physical condition of the superphosphate during and after mixing.Sufficient analytical data are included to indicate the chemical composition of the products. A more detailed study of factors affecting the chemical composition of superphosphate prepared from concentrated phosphoric acid will be given in a subsequent paper.Marshall, Rader, and Jacob (4) studied the reaction beh e e n phosphoric acid and phosphate rock as affected by the 1 Present address, Cniversity of Idaho, Moscow, Idaho. 973 924 ISDUSTRIAL AND ESGINEERING CHEIIISTRY VOL. 28, NO. 8quantity, concentration, and purity of the acid, the type and particle size of the rock, the time and temperature of mixing, and the time of storage of the mixtures. They investigated the effect of these variables upon the conversion of the P2Oj in the rock into available (citrate-soluble) phosphate. RIost of their data covered the range from 21 to 64 per cent H3P04. When 10 per cent excess of acid was used and the products were stored for 16 days, the percentage conversion was reported in one series of experiments to be i 5 per cent with 4 i per cent acid, 82 with 56 per cent acid, and 95 with 64 per cent acid. X'ith 75 per cent acid, rapid solidification of the mixture prevented uniform mixing. This probably m s due to the limitations of the mixing device. Berlin and co-workers ( I ) also investigated the preparation of superphosphate from apatite and concentrated phosphoric acid. These authors recommended the use of 70 to 80 per cent &Pod1 and 10 to 30 per cent excess of acid over that theoretically required. It was stated also that the reaction should be carried out by heating a t 40" to 100" C. for 3 hours. The apatite used seems to have been a type much more difficult to decompose than that commonly found in the United States. Concentration and Quantity of Ac...

No abstract

We have measured the isotope effect in stablized 7-uranium alloys and found T c ozM a , a= -0.53±0.02. We find r c »2.1°K to be a more representative value for the extrapolated superconducting transition temperature of a hypothetical pure 7-uranium than the previously reported estimate of 1.8°K.