- A sampling procedure for an aqueous hydrosoluble polymer solution flowing in a main circuit, enabling a sample to be collected to undergo at least one characterisation under ambient air characterised in that a stabilizing solution is added, according to a discontinuous addition method, to the aqueous hydrosoluble polymer solution, before or after sampling from the main circuit, so as to obtain a sample comprising a mixture of aqueous hydrosoluble polymer solution and stabilizing solution in which the hydrosoluble polymer is protected against attacks it may undergo in the absence of a stabilizing solution and in an atmosphere containing at least 10% by volume of oxygen, the procedure comprising a prior step of determining the volume of stabilizing solution to be added to the aqueous hydrosoluble polymer solution in which the volume of stabilizing solution added is varied and the change in measured viscosity of the mixtures of aqueous hydrosoluble polymer solution and stabilizing solution obtained is studied when the sample comes into contact with the ambient air over time; the sampling procedure making use of a sampling device connected to the main circuit in which the aqueous hydrosoluble polymer solution to be sampled is circulating, including; - a first vessel, called the sampling tank, containing the sample collected, said sampling device including: • an inlet for aqueous polymer solution to be sampled, and a sampling pipe connecting this inlet to the main circuit, the said sampling pipe being fitted with a non-shearing sampling closure and being connected to the main circuit and • an outlet and outlet pipe fitted with an outlet closure and connected to the outlet, - a second vessel, called the treatment tank, containing the stabilizing solution, comprising an outlet for the stabilizing solution, a connecting pipe connected to the outlet for the stabilizing solution and fitted with a treatment closure and providing, at least in part, the connection between the treatment tank and the sampling tank, and where the sampling tank is connected hermetically to the main pipe, and is isolated hermetically when the sampling closure, outlet closure and treatment closure, as well as any other closures that may be present to provide communication from the sampling tank to the outside, are closed. - a first vessel, called the sampling tank, containing the sample collected, said sampling device including: • an inlet for aqueous polymer solution to be sampled, and a sampling pipe connecting this inlet to the main circuit, the said sampling pipe being fitted with a non-shearing sampling closure and being connected to the main circuit and • an outlet and outlet pipe fitted with an outlet closure and connected to the outlet, • an inlet for aqueous polymer solution to be sampled, and a sampling pipe connecting this inlet to the main circuit, the said sampling pipe being fitted with a non-shearing sampling closure and being connected to the main circuit and • an outlet and outlet pipe fitted with an outlet closure and connected to the outlet, - a second vessel, called the treatment tank, containing the stabilizing solution, comprising an outlet for the stabilizing solution, a connecting pipe connected to the outlet for the stabilizing solution and fitted with a treatment closure and providing, at least in part, the connection between the treatment tank and the sampling tank,