a container 1 illustrated in fig1 and 2 comprises a rigid cylindrical container body 2 comprising glass or a polymer such as polypropylene . the container body 2 is provided with a lid 3 which comprises a porous cellulose dome which engages with the container body 2 allowing only soluble components to pass through it . the domed shape is designed to increase the surface area of the filter , thus allowing more effective solvent extraction . the lid 3 has a dual purpose , firstly to contain test material in the container 1 prior to analysis and secondly to separate the soluble components from insoluble components during solvent extraction . the container body 2 contains a porous filter 4 , the preferred design being a spirally wound expandable , slidable and rotatable polyester filter ( acting as a filtration membrane ) which exhibits hydrophilic and also oleophobic properties , this not only enhancing the drying process post hydrolysis but also the final solvent extraction . inside the container body 2 there is an internal shoulder 5 , acting as a stop when the filter 4 is moved towards the lid 3 ( see below ). in use , a sample ( not shown ) is introduced into the container body 2 . the lid 3 is affixed to the container 1 , thus trapping the sample therein and the container is re - weighed to obtain the weight of the sample . if the sample is a food or feed product and it is desired to determine its total fat content , a weight of the food product is placed in the container 1 . the sample then undergoes a hydrolysis process , which releases the bound fat , in the absence of the lid 3 . at completion of this stage , the water soluble phase is separated by filtration , draining out of the container body 2 , leaving behind the fats , oils and waxes and non - hydrolyzed material , which remain within the container body 2 . the porous nature of the filter 4 retains the hydrolyzed fats , oils and waxes and hydrolyzed material within the container body 2 . after the step of hydrolysis , e . g . by boiling in acid , has been completed , the container body 2 may be flushed with distilled water until the material contained within the container body 2 is free of acid . prior to solvent extraction , it is necessary to remove the water from the hydrolyzed sample and filter 4 , and this is achieved by sliding and expanding the filter 4 to its upper position against the shoulder 5 using a tool provided . the inventors have found that this process speeds up the drying procedure by increasing the surface area of the sample and filter 4 and reduces condensation . for this purpose , the bottom of the container body 2 may be open as shown or shaped to receive an appropriate tool . next , the container body 2 and its contents may be oven dried , e . g . in a microwave oven , prior to the final stage of solvent extraction . prior to the final solvent extraction , the filter 4 is rotated to a vertical position , this enhancing efficient solvent extraction , and the lid 3 is put in place on the container body 2 . fats , oils and waxes ( the crude ( or total ) fat ) of the sample are removed from the hydrolyzed material by subjecting the container and its contents to solvent extraction , the fats , oils and waxes being solubilized and collected in a pre - dried and weighed receiving receptacle which is finally dried and re - weighed . the increase in weight of the receptacle represents the total weight of fats , oils and waxes contained within the material and called in the art oil b . table 1 shows various determinations of oil b in various materials . each material was tested using the conventional prior art method described above and a method according to the invention , using the above - described container . the results for the prior art oil b method , and the method using the invention are each presented in columns , the left - hand column in each case containing experimental results , and the right - hand column containing the averages . as can be seen from the conventional prior art method , dried milk gave a mean value of 25 . 58 gms per 100 gms of sample with a range of 0 . 43 . the use of the present invention gave a mean value of 25 . 78 with a range of 0 . 12 . in general the use of the invention gave greater agreement between replicates than the conventional prior art method . it is thus possible to provide a filtration container for analytical use which functions both as a container and a filter element . this enables the transfer of materials to be eliminated , thereby giving an increase to experimental accuracy . the use of container 1 also increases the capability of a laboratory to perform many tests simultaneously . the container 1 may , in use , be held within a rack or carousel assembly which aids the placement and removal of one or more containers into and out of beakers containing reagents used in the analysis . the container may be used to perform a number of tests . an example of a test for the oil b content of a food is described below : 1 . for each test , weigh 1 . 5 - 2 . 0 grams of a sample into a container body 2 and place the container 1 into a carousel which can take several samples ( e . g . 6 ). 2 . if required , independently determine the dry matter content of each material using a standard oven drying method . 3 . measure out 350 mls of hydrochloric acid ( 3 molar ) and transfer to a first extraction beaker . 4 . lower the carousel gently into the beaker of solution and moisten the surface of each sample with acid using a disposable pipette . 5 . place the beaker on a pre - heated hotplate , replace the condenser and bring to a gentle boil under reflux conditions . this procedure is repeated for each set of tests . 6 . after 1 hour from the point of boiling , remove the beaker from the hotplate , cool to ambient temperature and remove the carousel from the beaker and allow the containers 1 to drain . 7 . discard the acid and solubles within the beaker and fill with purified water at ambient temperature . lower the carousel into the water , ensuring all the containers refill . remove the carousel and drain the containers and beaker and repeat until the washes become neutral , which may be tested with ph test paper . 8 . all drained containers are placed for a few minutes on tissue paper to remove excess water . 9 . using the tool provided , the internal filter 4 of each container 1 is expanded and repositioned to its uppermost limit . 10 . the containers containing the residues are oven dried to a constant weight in a microwave oven to remove the water . 11 . a filter lid 3 is fitted to each container 1 , a small plug of cotton wool inserted to retain the sample and each placed in a solvent extraction assembly and refluxed for a specific period . the fats , oils and waxes are collected within a pre - dried and weighed receptacle . 12 . finally , the solvent is removed from each receptacle , placed in a rack and oven dried ( 100 ° c .) to a constant weight and re - weighed . the increase in weight is reported as oil b . the oil b content can be calculated from the following equation :