The EACN scale for oil classification revisited thanks to fish diagrams.

The phase behavior of C(10)E(4)-oil-water systems at constant o/w ratio and variable temperature (fish diagram) has been investigated for several homologous oil families. The temperature T( *) and surfactant concentration C( *) at the critical point were determined for 10 n-alkanes varying from C(6) to C(28) as well as for a series of alkylcyclohexanes and alkylbenzenes. On the basis of T( *), equivalent alkane carbon numbers (EACN) were assigned to nonlinear alkanes, alkylbenzenes, and alkylcyclohexanes. The consistency of the method was shown by corroborating that the EACN values of oils previously investigated with other C(i)E(j) (dibutyl ether, squalane, isopropyl myristate, and dodecylbenzene) are the same when determined with C(10)E(4). The fact that two oils of different nature but with the same EACN (i.e., the same T( *)) do not exhibit the same C( *) is discussed in terms of monomeric solubility of the surfactant in the oil (CMC(oil)).

Carbon allocation to volatiles and other reproductive components in male Ficus carica (Moraceae).

Volatile compounds are often mediators of plant-pollinator interactions. Their emission is presumed to be costly, but this cost has seldom been quantified. Figs of Ficus carica (a dioecious species) release volatile compounds when receptive, thus attracting the agaonid wasp Blastophaga psenes. In dioecious fig species, wasps lay eggs inside male figs and pollinate female ones. For a male tree, we estimated carbon allocation to reproduction using the annual growth module (AGM) as the unit of measurement. Over the growing season, leaf and fig carbon exchange and construction costs were measured, as well as carbon investment in stamens, provisioning pollinators, and biosynthesis and release of volatile compounds. Representativity of the tree studied was evaluated by measuring some of these parameters on seven other male fig trees. The results show that 7.6-16.4% of the carbon assimilated by leaves and figs was invested in reproduction. Of the carbon invested in reproduction, pollinator attraction and feeding represented only 0.08-0.12% and 1.84-2.33%, respectively, while pollinator sheltering (fig construction and respiration) represented 97.6-98.0%. In this strict and coevolved plant-pollinator association, the main male reproductive investment was thus in the structures sheltering the associated pollinators.

The use of emulsions for the determination of methylmercury and inorganic mercury in fish-eggs oil by cold vapor generation in a flow injection system with atomic absorption spectrometric detection.

An on-line time based injection system used in conjunction with cold vapor generation atomic absorption spectrometry and microwave-aided oxidation with potassium persulfate has been developed for the determination of the different mercury species in fish-eggs oil samples. A three-phase surfactant-oil-water emulsion produced an advantageous flow when a peristaltic pump was used to introduce the highly viscous sample into the system. The optimum proportion of the oil-water mixture ratio was 2:3 v/v with a Tween 20 surfactant concentration in the emulsion of 0.008% v/v. Inorganic mercury was determined after reduction with sodium borohydride while total mercury was determined after an oxidation step with persulfate prior to the reduction step to elemental mercury with the same reducing agent. The difference between total and inorganic mercury determined the organomercury content in samples. A linear calibration graph was obtained in the range 0.1-20 micrograms l-1 of Hg2+ by injecting 0.7 ml of samples. The detection limits based on 3 sigma of the blank signals were 0.11 and 0.12 microgram l-1 for total and inorganic mercury, respectively. The relative standard deviation of ten independent measurements were 2.8 and 2.2% for 10 micrograms l-1 and 8.8 and 9.0% for 0.1 microgram l-1 amounts of total and inorganic mercury, respectively. The recoveries of 0.3, 0.6 and 8 micrograms l-1 of inorganic and organic mercury added to fish-eggs oil samples ranged from 93.0 to 94.8% and from 100 to 106%, respectively. Good agreement with those values obtained for total mercury content in real samples by electrothermal atomic absorption spectrometry was also obtained, differences between mean values were < 7%. With the proposed procedure, 22 proteropterous catfish-eggs oil samples from the northwestern coast of Venezuela were measured; while the organic mercury lay in the range 2.0 and 3.3 micrograms l-1, inorganic mercury was not detected.

Emulsiones: aspectos físico-químicos / Emulsions: physico-chemical aspects

Se ha estudiado la influencia de la formulación físico-química (salinidad de la fase acuosa, EACN del aceite, naturaleza del surfactante, naturaleza y concentración del cosurfactante), sobre la naturaleza y propiedades de los sistemas Surfactante-Alcohol-Agua-Aceite emulsionados. Dicha influencia se muestra en un diagrama bidimensional mixto generalizado (Formulación-Fracción volumétrica de fase acuosa, fw). A relaciones agua/aceite próximas a la unidad (30% 70%), la inversión depende fundamentalmente de la proporción volumétrica de las fases, es decir, está controlada por factores físicos. Basándose en los resultados obtenidos, se propone una clasificación general del tipo de emulsión, de acuerdo con la formulación óptima y las líneas de inversión. La existencia de correlaciones entre las diferentes variables de formulación en el óptimo, los fenómenos asociados y una regla lineal de mezclas, sugieren la utilización de un nuevo método de caracterización de surfactantes, más rápido y exacto que el método HLB. Experimentalmente se usan uno o dos surfactantes conocidos y el parámetro característico correspondiente, que puede ser el HLB, es independiente de las demás variables físico-químicas