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The phase diagrams of the CH 3 CH 2 OH + Cs 2 SO 4 + H 2 O system were determined at (10, 30, and 50) °C. The binodal curves were given using a five-parameter equation. The tie lines were correlated by the Othmer-Tobias and Bancroft equations. Samples of the solid phase analyzed by thermogravimetric analysis showed that it was the anhydrous salt.

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The e¡ects of dietary protein (DP) levels on the growth, digestibility, digestive enzyme activity and stress tolerance of Litopenaeus vannamei (Boone, 1931) were investigated in high-density (375 m^3) tank trials. Shrimps (6.2 AE 0.2 g) were fed diets with ¢ve di¡erent protein levels (31%, 35%, 39%, 43% and 47%) for 60 days. The results showed that variations in DP signi¢cantly (Po0.05) in£uenced the growth performance, digestibility, enzyme activity and their ability to tolerate stress.Weight gain showed a linear increase in relation to crude protein (CP) up to 43% and showed a slight decrease with a further increase to 47%. Feed conversion ratio was observed to be the lowest in CP 43%: 2.53. A higher protein e⁄ciency ratio was observed with the low-protein diet CP31 (1.07); however, it was not signi¢cantly di¡erent from the rest of the dietary treatments. Protein digestibility was the highest (75.71%) in CP47 and the lowest (71.94%) in CP31. Protease activity ranged between 63.7 and 70.2 (U Protein^1), and showed a positive correlation with the DP levels. Shrimp fed CP43 well tolerated a sudden decline in salinity and survived for 548.3 min in fresh water. Observations from this study indicate that a DP level around 43% could be optimum for L. vannamei in high-density culture systems in the absence of natural productivity.

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