Abstract: A laboratory device and method are adapted to subject a same rock sample to successive liquid treatments without any intermediary handling of the sample. The device combines a chamber comprising a first part fitted with an inlet for introducing a rock sample and liquid reagents into the chamber; a heater for regulating the temperature in the chamber and a plug fitted within an open port for protecting the chamber from an overpressure. The first part also comprises means for stirring the contents of the chamber including a liquid by introducing gas as bubbles into the liquid. A second part of the chamber is located under the first part and a selective filtering unit is interposed between the first and second parts of the chamber, the filter has a porosity selected for retaining organic material contained in the sample.

Abstract: Process for manufacturing citric acid by aerobic culture of yeast strains in a medium containing at least one n-paraffin, comprising adding to the culture medium, after the phase of exponential growth thereof, a nitrogenous heterocyclic organic compound selected from .alpha.-picolinic acid, 2,6-dipicolinic acid, quinaldic acid, bi-pyridine, orthophenanthroline, 8-hydroxyquinoline and 5-hydroxyquinoxaline, at a concentration from 0.5 to 10 g/liter, and controlling the pH value of said medium during said growth phase by addition of sodium or potassium carbonate.