Recibido en junio de 1991; aceptado en enetv de 1592 RESUMENSe estudió la recirculación del liquido residual de la etapa de pre-extracckkt y precipitaci6n en muestras de Maupcystis pyrifem, para minimizar el consumo de agua dulce en el proceso de extracción de alginato a nivel laboratorio. En la etapa de pre-extracción se demostró que al recircularlos hasta en tres ocasiones se obtuvo un rendimiento promedio de 28.44%, con ahorros del 2.5% del consumo de agua dulce del proceso y de 56.25% en el consumo de kido clorhkirico concentrado en esta etapa. Se redujo en 50% el consumo de agua dulce en el proceso, mediante tres recirculaciones del líquido residual de la precipitación en la etapa de extracción alcalina, mostrando un rendimiento promedio del alginato de sodio obtenido de 33.45%. Los alginatos de sodio obtenidos presentaron una alta viscosidad y valores de pH comprendidos dentro del intervalo de mayor estabilidad (pH S-9).The recirculation of the residual liquid from the preextraction stage and precipitation using samples of Macmqstis pyrijem was studied to reduce the consumption of fresh water in the process of alginate extraction in the laboratory. An average yield of 28.44% was obtained with three recirculations in the pre-extraction stage, with a saving of 25% in the consumption of fresh water and of 56.25% in the consumption of concentrated hydrochloric acid. The consumption of fresh water was reduced by SO% with three recirculations of the residual liquid from the *Becario de la COFAA-IPN.

Sodium and potassium alginates were extracted at the pilot plant scale from the giant kelp, Macrocystis pyrifera, from Bahía Tortugas, Baja California Sur, Mexico. Alginates were coded as S1, S2 and S3 for sodium alginate, and as P1, P2 and P3 for potassium alginate. The average viscosities of the sodium and potassium alginates in aqueous 1% solution were 58, 145 and 506 mPa s, and 48, 155 and 200 mPa s, respectively. Results showed that dental impresion material prepared with sodium alginate with extra low viscosities (S1 = 58 mPa s) and low viscosities (S2 = 145 m Pa s) did not form gels, the material prepared with medium viscosity (S3 = 506 mPa s) produced a gel type II (regular set) in 70% of the 10 formulations experimented, and the material prepared with potassium alginate with extra low viscosity (P1 = 48 mPa s) produced a gel type II in 90% of the formulations. Using potassium alginate with low viscosity (P2 = 155 mPa s), 90% of the formulations were type I (fast set), and using potassium alginate with medium viscosity (P3 = 200 mPa s), 80% of the formulations were type I. The highest compressive strength was obtained using sodium alginate of 506 mPa s and the three potassium alginates experimented at 25% concentration, with values of 2474, 1209, 2101 and 2124 g cm-2 for S3, P1, P2 and P3 alginates, respectively. The elasticity order of formulation with 25% alginates compared with a commercial product (Jeltrate®) was as follows: Jeltrate® > P2 > S3 > P3 > P1. It was concluded that S3, P1, P2 and P3 alginates have good potential for use in the production of dental impression materials.